Episode One

[Beach]

(The Tardis has materialised in mid-air just offshore, and set itself down gently on the water. The Doctor, Jamie and Victoria use a rubber dinghy to row to the shingle beach nearby.)
DOCTOR: There. Come one, Victoria, out you get.
JAMIE: Trust you to bring us right down in the middle of the sea.
DOCTOR: The Tardis is perfectly capable of floating you know.
VICTORIA: Where are we exactly?
DOCTOR: Oh England, undoubtedly.
JAMIE: Aye, you can tell by the weather.
DOCTOR: And the white cliffs.
VICTORIA: We always seem to land on this planet.
JAMIE: Aye, it's always England. I think by the hammering the Tardis has got, you've gone and spiked it. Hey, where are you going?
(Something further along the beach has caught the Doctor's attention.)
JAMIE: Hey what's all this stuff Doctor?
VICTORIA: Foam, you silly. You often get it on the sea shore.
JAMIE: Aye, but not in big lumps like this, hey Doctor?
DOCTOR: No, not usually, Jamie. (He scoops some up.) Hey Jamie, feel that.
(The Doctor pushes the foam into Jamie's face.)
JAMIE: Right.
(And the three have a foam fight up the beach. Then Jamie sees something further along.)
JAMIE: Hey, Doctor, what's that? May be that's where the foam's coming from.
DOCTOR: Oh, I hardly think so, Jamie.
JAMIE: Well, let's go and see.
(They come to a large steel pipe which curves up out of the sand and into the face of the cliff.)
JAMIE: What is it?
DOCTOR: It's just what it says, Jamie. It's EuroSea Gas.
JAMIE: Gas from the sea? Oh, who are you trying to kid?
VICTORIA: So it's nothing to do with the foam then.
DOCTOR: No, no, I shouldn't think so. I wonder what that is?
(The Doctor peers at a large black metal box fastened to the pipe, then tries to open it.)
JAMIE: Will it not budge?
DOCTOR: No, it won't touch it, I'm afraid, Jamie. Ah well, have to use this.
JAMIE: What's that?
DOCTOR: It's a sonic screwdriver. Never fails.
(The Doctor activates the wand-like device and the screws unwind themselves out of the box.)
DOCTOR: There we are. Neat isn't it? All done by sound waves. Now, what have we got here. Oh yes.
JAMIE: What is it? What's that noise?
DOCTOR: I don't know, Jamie.
(The Doctor closes the box, gets a stethoscope from his pockets and listens to the pipe. It sounds like a heart beat.)
VICTORIA: I can hear it too.
DOCTOR: Yes. It's probably only throbbing from a pump, you know.
VICTORIA: Doctor, please hurry up. I don't like this place. It's so quiet. I feel as if we're being watched.
DOCTOR: All right, Victoria. Now then, Jamie.
(They are being watched, through the telescopic sight of a remotely controlled rifle which is relaying the image to a television screen. The rifle moves to put its cross-hairs on the Doctor. The Doctor is shot in the shoulder, and falls.)
VICTORIA: Doctor!
(Jamie and Victoria are also shot.)

[Control hall]

(Victoria wakes. She is lying on the floor of a brightly lit room with two armed guards standing over her.)
VICTORIA: Doctor? Doctor?
DOCTOR: Victoria? Jamie, you there?
JAMIE: Oh, I think so.
VICTORIA: I can't move. My legs.
JAMIE: What happened?? What do you want?
DOCTOR: Would someone kindly tell us where we are, please? Why don't you answer?
JAMIE: Come on, where are we?
VICTORIA: What have they done? Can't move.
DOCTOR: I think we've been tranquillised, Victoria.
JAMIE: Eh?
DOCTOR: Tranquillised.
JAMIE: Who do they think they are?
ROBSON: We should be the ones asking the questions. I shall expect quite a lot of answers.
JAMIE: What is this place?
ROBSON: You mean you don't know?
JAMIE: If only I could just get up.
ROBSON: I wouldn't try if I were you.
DOCTOR: You know, in this position it's just a little difficult to communicate.
HARRIS: Shall we give them some U4, sir?
DOCTOR: Eh?
ROBSON: Yes, do that Mister Harris.
JAMIE: What's U4?
VICTORIA: Oh no.
DOCTOR: I think it's all right, I think it's the antidote.
VICTORIA: No, please.
DOCTOR: Anyway, there's nothing we can do about it, you know. Oh yes, thank you. Yes, that's better, thank you. Thank you very much. Yes.
(Revived by the antidote gas, the travellers stand.)
ROBSON: You were on the beach by the pipe line, in a restricted area. Now why?
VICTORIA: We were lost, that's all.
ROBSON: You were tampering with the emergency release valve remote control. You're a saboteur.
VICTORIA: He's not. He's a doctor.
DOCTOR: I can assure you. I was only being curious.
HARRIS: I don't really think how they could have anything to do with the fall in pressure
ROBSON: When I want your opinion, Harris, I'll ask for it. In the meantime, lock them up in one of the cabins. I'll interrogate them later. And you lot, get back to work.
JAMIE: Is he always as charming as that?
HARRIS: We're in something of an emergency at the moment. You see, we've just lost contact with one of our rigs at sea.
DOCTOR: You mean communications have broken down?
HARRIS: No, that's what's curious about it. As far as we can tell our video link is functioning normally. The crew just aren't answering.
VICTORIA: You can't blame us for that, surely.
HARRIS: There's also been a drop in pressure in the feed lines from the rigs. You were seen tampering with a release valve on the pipe line.
DOCTOR: I told you I was merely being curious.
HARRIS: Were you?
JAMIE: Are you calling us liars?
HARRIS: No, but you must admit your sudden appearance here inside our restricted area is suspicious.
VICTORIA: That's no reason to shoot us down like animals.
HARRIS: Maybe not, but we were under a security alert and Mister Robson's, well. under considerable pressure himself. I'm sorry but I shall have to do as he says and lock you up.
DOCTOR: Oh dear.
HARRIS: Would you follow me? Come along, this way.
(Harris leads the way and the two armed guards follow. A warning light starts to glow on a control panel.)

[Compound entrance]

(Harris's wife is stopped from leaving.)
GUARD: May I see your pass please, madam?
MAGGIE: Pass?
GUARD: I have instructions that no one is to leave or enter the compound without a written pass from Chief Robson. Not until after the emergency.
MAGGIE: But you know who I am. My husband is second in command to Chief Robson.
GUARD: Yes Mrs Harris, I know.
MAGGIE: Then let me pass. Please.
GUARD: Sorry, madam. I think you should return to the residential block.

[Crew bunk room]

HARRIS: I'm sorry, but there's nothing I can do to help you until you tell me what you were doing with that release valve on the pipe line.
DOCTOR: It wasn't the valve I was interested in.
HARRIS: Oh?
DOCTOR: I heard a movement coming from inside the pipes.
HARRIS: A movement? (to guard) Oh, it's all right. You can go.
DOCTOR: Yes, movement. Don't ask me what it was.
HARRIS: Well, I'm not sure what you re trying to suggest, but I can assure you marine life couldn't possibly get inside the pipe line tube. It would never get pass the drill pumps.
JAMIE: Aye, that's as maybe, but there was something inside that tube because I heard it too.
VICTORIA: And so did I.
DOCTOR: But if the pressure is down in the pipes, perhaps that's the reason why? Perhaps marine life has got into the pipes.
HARRIS: But that's impossible. We spent years of time, money and research into perfecting our emergency system.
DOCTOR: Well, perhaps there's a fracture in the pipes. A break, and something's got in that way.
HARRIS: Oh, I doubt it.
DOCTOR: Mister Harris, I don't wish to appear interfering but don't you think it'd be a good idea to turn off the gas? At least until you've had a chance to check.
HARRIS: Chief Robson would never agree to that.
DOCTOR: Why not?
HARRIS: Well, he doesn't believe in working to the book. He prides himself that the flow has never been shut off ever since he took charge.
DOCTOR: He sounds a very silly man.
HARRIS: But he appears to be right about one thing. You seem to know quite a lot about our business.

[Control hall]

PRICE: Chief?
ROBSON: Yes?
PRICE: We've gained contact with Rig D. Come in, Rig D. Come in, please. Rig D, can you hear me please?
(There is interference on the signal.)
CARNEY [on monitor]: Yes. Rig D to HQ. I can hear you.
ROBSON: Carney? What the dickens is going on out there?
CARNEY [on monitor]: Everything's quite all right, Mister Robson.
ROBSON: What?
CARNEY [on monitor]: We have the situation under control.
ROBSON: Will you speak up, man. I can't hear a word you're saying.
CARNEY [on monitor]: Don't worry.
ROBSON: Price, are we losing volume?
PRICE: No, sir. I don't understand it. Will you speak a little louder, Mister Carney?
CARNEY [on monitor]: Everything is under control.
ROBSON: Carney? What happened to the emergency crew we sent you? Have they arrived yet?
CARNEY [on monitor]: Yes. Yes. But they must stay here for the time being.
ROBSON: They what?
CARNEY [on monitor]: We've had a slight accident. Two men out of action.
ROBSON: Now listen, Carney. You get that rig fixed A1 and quick.
CARNEY [on monitor]: But it will take some time.
ROBSON: What? What did you say? What's wrong with this thing.
PRICE: I don't know, sir. It must be their end. He seems to be whispering.
CARNEY [on monitor]: Everything's under control.
ROBSON: Carney, speak up man!
CARNEY [on monitor]: Everything's under control.
ROBSON: Carney!
CARNEY [on monitor]: Everything's under control.
ROBSON: Carney!
PRICE: I think we've lost contact again, sir.
ROBSON: Well fix it, man.
(Harris enters.)
ROBSON: Price is getting too old for his job.
HARRIS: Mister Robson, I think we should turn off the gas flow coming from the rigs and make a check.
ROBSON: You think what, Mister Harris?
HARRIS: That Doctor chap, the stranger. He said he heard a movement coming from inside the pipe line on the beach.
ROBSON: Oh, did he now. Did he say what he thought it was? Mice?
CHIEF: Chief? She's down a further three. Pressure's on just one fifty seven.
ROBSON: One fifty seven? Are you sure?
CHIEF: Yes, sir.
HARRIS: That means the gas flow pressure is down at the rate of three percent every
CHIEF: Twenty minutes.
HARRIS: Doesn't this prove that something must be blocking the pipe line?
ROBSON: It proves nothing of the sort. It's probably a faulty gauge, that's all. Check it.
HARRIS: Look, at least give us the benefit of the doubt.
ROBSON: When you want to find out about pipe lines and rigs Mister Harris, the thing to do is to go out to sea and work on them.
HARRIS: Look, I'm merely saying that if something had got into the tube then we should check
ROBSON: You let me worry about that.
HARRIS: But Mister Robson, please listen. Look, this ties up with what I've been trying to tell you. For three weeks now, there's been a regular and increasing build up of fall in pressure. Look, I think you should at least look at my calculations. The time ratio of the increases and falls corresponds to form a definite progressive pattern.
ROBSON: So?
HARRIS: I'll get them.
(There is an open briefcase nearby.)
ROBSON: What are you trying to prove, Harris? That I don't know my job?
HARRIS: No, sir, just that I do know mine. It's your decision whether to take notice of my work but I must put it on record that I have offered the information.
(A white gloved hand takes some papers from the briefcase.)
ROBSON: Don't threaten me, boy. I've eaten upstarts like you for breakfast. You think you can baffle me with your little bits of paper, don't you. All right, you go ahead and get them and I'll show you where you've gone wrong.
(Harris goes to get the file.)
ROBSON: Did you make a thorough check?
CHIEF: Yes, I checked it. Seems to be working properly.
HARRIS: It's gone.
CHIEF: Doesn't seem to be anything wrong with her.
HARRIS: It's gone. The file's gone.
ROBSON: Well, well, well. Has it now.
HARRIS: I'm sure I put it in here this morning. I must have left the file on my desk at home. I'll go home and get it.
ROBSON: You won't. You'll stay here. I'm not doing your job as well as my own.
HARRIS: What's the matter, sir? Are you scared that I might prove you wrong?
ROBSON: No, you go ahead. But you'd better have something more than a high flown theory, because if you haven't I'm going to take you and chop you up into little pieces and throw you back to your crummy little university. All right?

[Crew bunk room]

(Jamie is standing on the Doctor's shoulders.)
DOCTOR: I've got it.
(He passes down a grille taken from an opening above the door.)
DOCTOR: Can you see anyone?
JAMIE: All clear.
DOCTOR: Do you think you can make it?
JAMIE: Of course I can make it. Hold on.
VICTORIA: Don't bother, Jamie. I can do it with this.
JAMIE: Pick a lock with A hair pin? Don't be daft.
(Jamie slips. The Doctor cries out in pain.)
VICTORIA: Clumsy.
(Victoria works on the lock as Jamie sticks his head out into the corridor.)

[Refinery corridor]

HARRIS: Maggie, where have you been? I've been trying to contact you.
MAGGIE: I was on my way to the village but Robson's clamped down on security. I'm just coming to find you to get a pass.
HARRIS: Yes, there's been a bit of a flap on.
MAGGIE: Well can I have a pass?
HARRIS: Not at the moment. Look, could you do something for me?
MAGGIE: Yes, what is it?
HARRIS: There's a file. It's probably in the middle drawer of my desk in the study. Could you get it and bring it to me at the control room?
MAGGIE: All right, darling. What's the panic?
HARRIS: I'll explain later. Don't be long.
MAGGIE: All right, darling.
(Maggie watches Harris leave, then heads off.)

[Crew bunk room]

(Jamie stopped trying to get through the grille because the previous scene was right outside their door.)
VICTORIA: Oh, he's stuck.
DOCTOR: No, he's not. Are you ready, Jamie?
JAMIE: Yeah.
DOCTOR: Right.
(The Doctor gives Jamie a huge shove, and he falls through the grille into the corridor. Then the door opens.)
VICTORIA: Told you not to bother.
DOCTOR: Sorry about that, Jamie.

[Harrises' quarters]

(Maggie looks for her husband's file in the study. It's a mess.)
MAGGIE: Typical.
(She finds the file in a different drawer than Harris said. It has something inside it. Maggie opens it and drops it when she is stung.)
MAGGIE: Seaweed?
(She carefully picks up the file and the seaweed, then goes to the garden door and throws the seaweed onto the patio. Unnoticed, the seaweed bubbles and writhes.)

[Impeller room]

VAN LUTYENS: (Dutch) Mister Robson? Mister Robson? Could I speak with you please?
ROBSON: van Lutyens. I thought you were out at the control rig.
VAN LUTYENS: I just got back on the supply boat.
ROBSON: Something wrong?
VAN LUTYENS: I'm not quite sure. The men out there seem very restless.
ROBSON: Restless? What are you talking about?
VAN LUTYENS: You lost contact with Rig D, didn't you?
ROBSON: Yes. It was only a temporary fault. We regained contact within the hour.
VAN LUTYENS: Well, why didn't you tell us that? Unusual incidents like that only cause tension on the rigs.
ROBSON: Don't tell me what happened out on the rigs. I spent four years on one of those things without a break.
VAN LUTYENS: Then you should know better than anyone how important it is to keep up the morale of the crews.
ROBSON: What do you want me to do, wipe their noses for them? Mind your own business, Van Lutyens.
VAN LUTYENS: Mister Robson. I think you're forgetting we also have an interest in EuroSea Gas.

[Control hall]

ROBSON: We?
VAN LUTYENS: I'm here for the Dutch Government, not for myself.
ROBSON: You're here to offer me your expert advice, not to spread alarm amongst my crews.
VAN LUTYENS: How dare you say that to me?
ROBSON: I didn't ask you to come here. It was Megan Jones and those fools on the board. I said it wouldn't work and it never has.
VAN LUTYENS: Only because you are too proud to accept advice.
ROBSON: Let's get one thing straight, my friend. When I need your advice I'll ask for it.
(Robson walks away.) 
VAN LUTYENS: U stomme pompouze idiot Engelsman.

[Control hall walkway]

(From the walkway above the control hall, the Doctor, Jamie and Victoria watch van Lutyens leave.)
JAMIE: What was all that?
DOCTOR: I think he's Dutch, Jamie, and I don't think he likes the English very much.
(The Doctor gestures Jamie to keep quiet as Price answers an incoming call.)

[Control hall]

PRICE: Control.
BAXTER [OC]: Chief Baxter, Control Rig. Is Mister Robson there?
PRICE: Yes, sir. Mister Robson, sir.
ROBSON: Yes?
PRICE: Chief Baxter, Control Rig, sir.
ROBSON: Right. Yes, Baxter, what is it?
BAXTER [OC]: Has Mister Lutyens arrive there yet, sir?
ROBSON: Yes. Why?
BAXTER [OC]: Then he'll have told you how the men feel, sir.
ROBSON: Now listen, Baxter. I'm in charge of this outfit, not van Lutyens. You take orders from me not him.
BAXTER [OC]: Yes, sir. But there's something else.
ROBSON: What else?
BAXTER [OC]: Something seems to have got inside the pipe line.
ROBSON: Inside the pipe line?
BAXTER [OC]: We've all heard it.
ROBSON: Heard what?
BAXTER [OC]: This sound. At first I thought it was something to do with the pumps but it isn't. It's a peculiar sound. A sort of regular thumping, pulsating, like a heart beat.

[Control hall walkway]

DOCTOR: That's the noise I heard on the beach.
VICTORIA: What is it, Doctor?
DOCTOR: I don't know but we're going to find out. Come on, Jamie. Oh Victoria, no. Not you.
VICTORIA: Why not?
DOCTOR: I think it'd be better if you stayed back in the bunk room. Please.
VICTORIA: Oh, all right.
JAMIE: Oh, and Victoria?
VICTORIA: Yes?
(Jamie laughs. Victoria reluctantly goes back towards the bunk room, but as soon as Jamie and the Doctor are out of sight she turns around and goes exploring.)

[Harrises' quarters]

(Maggie is feeling ill after being stung by the seaweed. She goes to the videophone.)
PRICE [on monitor]: Control.
MAGGIE: Mrs Harris here, married block 420. Could I speak to my husband please?

[Control hall]

ROBSON: Have you recalibrated?
PRICE: I've just done phase two.
ROBSON: Better start on phase three.
HARRIS: Mister Robson.
ROBSON: Yes, Harris. Where are your figures?
HARRIS: Oh I haven't got them, sir. I sent my wife for them, but she's not well. I wondered if I could go and
ROBSON: No I would not. Tell her to call a doctor, not pester you.
HARRIS: But Doctor Patterson is still out at Rig D, sir.
ROBSON: Well, tell her to get one in from the outside.
HARRIS: But you've still go the compound on full emergency alert, remember?
ROBSON: All right. But make it quick.

[Oxygen store room]

(Nearby, in an oxygen cylinder store room, a person in white gloves and gas mask is adjusting valves and allowing the contents to leak out. He stops when he hears someone outside. It is Victoria, creeping along the corridor. She hears someone approaching and goes through the nearest door. The oxygen-rich atmosphere is stifling, so Victoria starts closing the valves. She hears a sound behind her and sees the tall thin man in the gas mask leave. He locks her in.)
VICTORIA: Oh, well.
(Victoria unpins her hair and starts to pick the lock. Outside, the mystery man activates the emergency ventilator control then leaves. There is a hum, and a metal grill in the wall opens.)

[Impeller room]

(Next to the Control hall. There is a large cylindrical machine and next to it an airlock to a lift shaft which goes down into the ground.)
JAMIE: What's that thing supposed to do?
DOCTOR: It's an impeller, Jamie. It pumps gas from the main pipe line out at sea. Come on.

[Pipeline room]

(Next door is a massive room full of pipes and pressure gauges. It has a raised observation platform at one end.)
JAMIE: Is this the pipeline, then?
DOCTOR: Yes, yes, they all are. It's a continuation of the pipe we found on the beach.
JAMIE: That bit there, you can see inside the pipe.
DOCTOR: Yes, It's transparent for checking condensation, and anything else that might get inside.

[Oxygen store]

(Victoria's lock picking skills have failed her. She thumps on the door instead.)
VICTORIA: Hello? Is anybody there? Oh, come on.
(There's a strange bubbling noise coming from the far side of the room. A mass of foam comes out of the ventilator grille. Victoria sees something moving within the foam.)

[Pipeline room]

(The Doctor is using his stethoscope on the main pipe.)
DOCTOR: There it is again, Jamie. Can you hear it?
JAMIE: Aye. What is it?
DOCTOR: Your guess is as good as mine. There's something inside there.
VICTORIA [OC]: Doctor!
DOCTOR: Victoria! Come on!

[Refinery corridor]

VICTORIA: Jamie!
(Victoria's cries can be heard echoing all around the pipes and corridors.)
VICTORIA: Help!
DOCTOR: Victoria, where are you?
VICTORIA [OC]: Doctor! Jamie! Help!

[Oxygen store]

(Tendrils of seaweed come through the vents, reaching for Victoria. She screams.)

Episode Two

[Refinery corridor]

DOCTOR: Come on, Jamie.
JAMIE: In here!
DOCTOR: I can smell gas!
(The Doctor and Jamie force open the oxygen storeroom door and pull Victoria out into the corridor.)
DOCTOR: Here you are.
(Robson, Van Lutyens and the Chief engineer enter.)
JAMIE: What happened?
DOCTOR: Deep breaths. Take deep breaths.
CHIEF: Mister Robson, in here. Gas.
ROBSON: Check it then. Find out what it is.
VICTORIA: Oh, Doctor, a horrible creature.
DOCTOR: Creature?
VICTORIA: Didn't you see it? It was in there. It came straight towards me covered with seaweed and foam and this horrible hissing sound, and then I screamed. I didn't know.
DOCTOR: All right, Victoria.
ROBSON: Creature? The girl's hysterical.
CHIEF: Mister Robson? They're empty. The seals are broken.
ROBSON: Why were you in there?
VICTORIA: I was hiding. I heard someone coming so I went in.
ROBSON: This door is always kept locked. You broke in. You emptied those cylinders, didn't you.
VICTORIA: Oh, no, no. It was open and someone locked it behind me.
JAMIE: She's telling the truth. The door was locked from the outside.
VAN LUTYENS [OC]: Mister Robson.
DOCTOR: Yes, it was locked.
VAN LUTYENS: This room wasn't full of oxygen when we came in here. It was another gas of a toxic composition.
ROBSON: All right, if it was a poison gas, where did it come from?
CHIEF: What about up there?
VAN LUTYENS: The ventilator's open. Good. Did you open the ventilator?
VICTORIA: No, it opened by its self.
JAMIE: Then whoever locked you in must have opened it. But how?
VAN LUTYENS: From here.
(Van Lutyens points to the ventilator control panel.)

[Harrises' quarters]

HARRIS: What is it, love?
MAGGIE: I don't know. I feel so dazed. And my hand.
HARRIS: Let me see. It looks all right. What happened?
MAGGIE: I don't remember.
HARRIS: You said you were stung or something.
MAGGIE: Did I? Why, I don't. Yes, yes it must have been. I went to get the file you asked for, put my hand inside and then. The seaweed.
HARRIS: All right, my love. Lie still and rest. Shall I get you some food, a glass of milk or something?
MAGGIE: Darling, you couldn't even boil an egg.
HARRIS: You shouldn't have married a scientist then.
(Maggie gasps for breath.)
HARRIS: Maggie!
MAGGIE: Darling. Darling. Darling.
HARRIS: Maggie!
(Out on the patio, the discarded seaweed is surrounded by a mass of foam which pops and hisses as Maggie becomes more agitated.)
HARRIS: What is it, love? What's the matter?
MAGGIE: I don't know. I just feel
HARRIS: I'd better get you a doctor. I'll go back and see if Doctor Patterson's returned yet from Rig D. Will you be all right?
MAGGIE: I think so.
HARRIS: Well if he isn't back, there's this other doctor. He might be able to help. I won't be long.
(Harris leaves. Maggie lies staring at the ceiling for a few moments, but the pounding gets louder in her head. She gets up and goes to the study, then to the patio door. She hesitates then opens it and stares at the weed. Suddenly she slams the door shut and stares at the floor in confusion.)

[Impeller room]

ROBSON: So what's the panic?
CHIEF: It's the pump, sir. The revs have dropped.
VAN LUTYENS: The pump is slowing down?
CHIEF: Yes, she's not holding steady even now. I don't understand it.
ROBSON: Well, don't stand there thinking about it, man. Do a complete check.
DOCTOR: Excuse me, may I say something? When I was in the pipe room a short while ago, I'm sure I heard a movement coming from inside the pipe.
VAN LUTYENS: What kind of movement?
DOCTOR: Well, the same as I heard on the beach. A sort of thumping sound.
VAN LUTYENS: But that's what they heard out at the rigs.
ROBSON: What you heard and what everybody else heard was a mechanical fault somewhere along the line.
DOCTOR: Then why did they hear it out at the rigs?
ROBSON: Because, my friend, underneath this impeller shaft is a vast steel gasometer buried in the earth. It acts like an echo chamber. It'll make the sound of a pin dropping sound like that of a thunder clap. It travels along the pipe.
DOCTOR: Oh, this wasn't a mechanical sound.
ROBSON: All right then, suppose there is something in the pipe. A fish or something. What do you expect me to do about it?
DOCTOR: Turn off the gas flow. At least until you've had a chance to investigate.
ROBSON: That's out of the question.
VAN LUTYENS: Mister Robson, if there is something in the pipeline
ROBSON: We do not turn off the flow and that is final.
CHIEF: Mister Robson, sir.
ROBSON: Yes?
CHIEF: Down another half.
ROBSON: It must be a mechanical fault. Get a couple of men and check, man, check.
VAN LUTYENS: If you allow the pressure to build up in the pipeline, you'll blow the whole rig sky-high.
DOCTOR: And blow us with it.
VAN LUTYENS: All because you're too stubborn to turn off the gas.
ROBSON: All right, what do you think it is? One of these creatures the hysterical girl thought she saw?
DOCTOR: Well, who knows.

[Control hall]

JAMIE: You mean to say that this place supplies all the gas for the whole of the south of England?
PRICE: And the whole of Wales.
VICTORIA: What are all those lights for?
PRICE: Well, that's a plan of the entire compound and each of those lights represents a remote control camera that I can switch through to this screen if I want to look at any particular area. Like this.
JAMIE: Oh. Where are all these rigs people talk about?
PRICE: Well, they're out at sea, of course, but that plan over there shows you the relative position of all the rigs under our command.
VICTORIA: What's the big one in the middle?
PRICE: Well that's the central control rig complex, the sort of the nerve centre of the whole thing. The other rigs feed her with gas and she in turn pumps it to us via the main pipeline, see.
VICTORIA: How awful to have to live out at sea. And lonely.
PRICE: Oh, I don't know. Mister Robson once spent four years on one of the early rigs without ever going ashore.
JAMIE: Aye, that would account for quite a lot.
VICTORIA: Jamie!
ROBSON: Hey, you. Come in here and give a hand.
JAMIE: Doesn't that man ever call anyone by their name?
PRICE: Well, it probably means trouble if he does. No, he's all right, is Robson. Certainly knows all there is to know about rigs, anyway.
HARRIS: Price! Has Doctor Patterson returned from Rig D yet?
PRICE: No, sir.
HARRIS: Where's your friend, the Doctor?
JAMIE: In there.

[Impeller room]

HARRIS: Doctor! Doctor, I need your help. It's my wife, she's very ill.
DOCTOR: Well, I'm not sure that I
HARRIS: You must come.
ROBSON: He will not go with you.
HARRIS: This is an emergency. It's my wife.
ROBSON: These people are in my custody until I decide what to do with them.
HARRIS: But my wife!
ROBSON: Don't bring your domestic affairs into the refinery, Harris. That goes for the rest of you.
HARRIS: Mister Robson, my wife is ill. If anything happens to her, I'll
ROBSON: All right, one hour.
HARRIS: Thank you. Doctor, please, this way.

[Harrises' quarters]

(Meanwhile, Maggie has left the study when there is a ring on the doorbell. Two almost comical figures are on the doorstep.)
OAK: (short, fat) Mrs Harris?
MAGGIE: Yes.
OAK: We are maintenance controllers, madam. I wonder if we might have a few words with your husband?
MAGGIE: Oh, my husband isn't here. He's at the compound.
OAK: Oh dear, that does make it rather difficult. We've come to carry out an inspection.
MAGGIE: Inspection?
OAK: In the kitchen. Your husband didn't tell you?
MAGGIE: No. Couldn't it wait until another day? I'm not feeling very well.
OAK: I'm sorry, madam, it has to be carried out without delay. Chief Robson's instructions.
MAGGIE: That man never stops giving instructions, does he. Oh, I suppose you better come in then.
OAK: Thank you. My name is Mister Oak and this is my colleague, Mister Quill.
(Quill is tall and thin.)
MAGGIE: Yes, well, please, be quick. I'm really not very well.
OAK: Of course, madam. Now don't you worry about us, Mrs Harris. You won't even know that we're here. Will she? The bag, Mister Quill.

[Impeller room]

CHIEF: Mister Van Lutyens.
VAN LUTYENS: What is it?
CHIEF: Feed line from the Control Rig. An excessive pressure build up in the pipeline.
VAN LUTYENS: She's almost up to capacity.
CHIEF: She'll blow herself wide open.
VAN LUTYENS: So there's a build up in the pressure coming in from the rigs and a drop in the pressure of the flow going out to the receiving stations.
CHIEF: There must be something interfering with the impeller itself.

[Control hall]

PRICE: Mister Robson, sir.
ROBSON: Yes.
PRICE: This is from Control Rig, sir. They say there's a pressure build-up in their feed line to us.
ROBSON: Right. Ask them how much, will you?
PRICE: Yes, sir.
VAN LUTYENS: Almost up to danger level, Mister Robson. Shall I give the order to turn off the gas?
ROBSON: You will not, Mister Van Lutyens.
VAN LUTYENS: There'll be an explosion any minute.
ROBSON: There will not be an explosion.
VAN LUTYENS: There must be if you don't turn off the gas.
ROBSON: Open release valve Section D, full pressure, will you?
VAN LUTYENS: What are you doing, man? It's too late for that. You can't possibly release enough gas in time.
ROBSON: You want to bet, Mister Van Lutyens?

[Harrises' quarters]

(Maggie is lying down on the bed. Oak and Quill are working on the gas cooker in the kitchen. There are tendrils of seaweed sticking out from Oak's overall sleeves. He puts on a pair of white gloves, just like Quill is already wearing. They go through to the study and open the patio door. The patio is covered in foam and seaweed now, and it starts to come into the house. Maggie gets up and goes to comb her hair, then realises that Oak and Quill are in the bedroom with her.)
MAGGIE: What are you doing in here? Is there something that you want?
(Oak and Quill move towards her, mouths open wide. Maggie can't breathe as she inhales the toxic gas they are giving out, and collapses. Meanwhile, out on the beach, an outlet valve vents excess gas.)

[Impeller room]

CHIEF: It's down. The pressure in the pipeline, it's back to normal.
VAN LUTYENS: Dank uw geluk. I wouldn't have thought you could possibly have done it in the time.
ROBSON: When you have too much gas in the tube, you release it. Didn't they teach you that much back at evening classes in the Hague, Mister Van Lutyens? Contact Chief Baxter, Control Rig, will you? Tell him the immediate crisis is over. Oh, and contact the other rig chiefs.
PRICE: Right.
VAN LUTYENS: But the feed out to the receiving stations is still dropping. The impeller is still slowing down.
ROBSON: What's the matter with you, Van Lutyens? You've been trying to teach me my job ever since you came here. I've been drilling for gas in the North Sea for most of my life. I don't need people like you or Harris to teach me how to do it.
PRICE: Mister Robson, sir. It's C Rig, sir. I can't raise them. No response at all.
VAN LUTYENS: So, the immediate crisis is over, ja?

[Harrises' quarters]

HARRIS: Maggie, I've brought the Doctor.
VICTORIA: Oh no, it's the same
DOCTOR: I smell gas. There's gas in this house.
HARRIS: Doctor, in here.
(Harris finds Maggie on the bedroom floor.)
DOCTOR: Jamie, the window, quickly!
JAMIE: Give me a hand.
(They break the window.)
HARRIS: Maggie.

[Control hall]

PRICE: I'm sorry, sir, I can't raise them.
VAN LUTYENS: Well, are you pleased with what you have done?
ROBSON: I'm warning you, Van Lutyens.
VAN LUTYENS: And I warned you, but you are too koppig, too stubborn to listen. Look at the facts, man. The fact that we lose contact with two rigs, have unprecedented, inexplicable pressure variations for over three weeks.
ROBSON: Oh, so that's it. You've been talking with Harris, eh?
VAN LUTYENS: Ja, Mister Harris did show me his figures. Only because you refused to listen to him. That's why I went out to the Control Rig, to see if there was an explanation out there.
ROBSON: And what did you find? Nothing. I'll tell you why. Because there's nothing to find.
VAN LUTYENS: All the same, Mister Harris' figures
ROBSON: Are bunk! And the rest of his tuppenny ha'penny tin-pot ideas. He's still a school kid with his bits of paper and his graph and his slide rule. You think I'm going to take any notice of him? I know every nut and bolt on every one of those rigs out there.
VAN LUTYENS: All right! So your prejudice prevents accepting Mister Harris' calculations. But what about me? Do you treat my opinion with as much contempt?
ROBSON: You? You are here to offer me your expert advice, but I'm not obliged to take it. I run this outfit the way I think fit. Is that understood?
CHIEF: Mister Robson, the impeller. Quick, two men.

[Impeller room]

CHIEF: She's down to a hundred and forty revs. Something must be jamming it at the base.
(The impeller slows and stops.)
VAN LUTYENS: Well, Mister Robson, where do we go from here? Come on, now. You have all the answers, don't you?
CHIEF: Wait a minute. Quiet!
VAN LUTYENS: What is it?
CHIEF: I think I can hear something.
(It's a heartbeat.)

[Harrises' quarters]

VICTORIA: Is she dead?
DOCTOR: Oh, no, no, no.
HARRIS: What's the matter with her?
DOCTOR: Well, she's in some sort of coma. Possibly because of this gas. It was toxic.
HARRIS: It isn't possible there could have been a gas leak in the flat. Besides, natural gas isn't toxic.
DOCTOR: Well, this isn't natural gas. This is the gas we found when Victoria was locked in the Oxygen room.
HARRIS: But where could it have come from?
DOCTOR: I don't know. What was the matter with her before this happened?
HARRIS: Well, she said she'd been stung by some seaweed or something.
JAMIE: Seaweed?
HARRIS: I asked her to get a file from my study, and she found the seaweed inside it.
DOCTOR: Did you put it there?
HARRIS: Well, no, of course not.
DOCTOR: There's no marks or abrasions.
HARRIS: No.
VICTORIA: Doctor?
DOCTOR: Um.
VICTORIA: What's this?
DOCTOR: What. Oh!
JAMIE: A bit of seaweed. What's it doing in here?
DOCTOR: It's still wet.
HARRIS: Perhaps it's the same sort that Maggie was talking about.
DOCTOR: No, don't touch it.
HARRIS: Why?
DOCTOR: Well in the first place, you don't want to get stung like your wife, do you? And in the second place, whoever put it in your file meant you to touch it.
HARRIS: But that's ridiculous. Wait a minute. I was sure I put that file in my briefcase this morning, but it wasn't there when I went to get it. I was on my way home when I met Maggie. But why? Why should anyone want me to get stung by a piece of seaweed?
VICTORIA: Well I hate the stuff. It's so slimy and horrid.
JAMIE: Och away, you've seen seaweed before, haven't you? There was loads of it down by the pipeline this morning.
DOCTOR: By the pipeline?
JAMIE: Aye, the place was overrun with it.
VICTORIA: Well not like that. It didn't move.
JAMIE: Move?

[Impeller room]

(Van Lutyens has been studying the refinery layout in his office. He goes to the impeller room.)
CHIEF: I want them all checked. Every remote control release valve on the line. And check and double check all those circuits.
VAN LUTYENS: Excuse me, Chief, could I have a word with you please?
CHIEF: Yes of course.
VAN LUTYENS: The impeller is still not functioning, ja?
CHIEF: No, it's not.
VAN LUTYENS: And that sound we heard, have you heard it again?
CHIEF: No. As Mister Robson says, it's probably just a mechanical fault.
VAN LUTYENS: You believe that?
CHIEF: Well it's really not my job to
VAN LUTYENS: Ah, come on, man. You're the Chief Engineer. The impeller is your responsibility.
CHIEF: It's not my job to formulate theories, it's Mister Robson's.
VAN LUTYENS: Robson! Robson! What's the matter with you all? Are you frightened of him or something?
CHIEF: No, Mister Van Lutyens, I just respect his judgement.
VAN LUTYENS: Well, I'm sorry, Chief. Could I have a word with you in private?
CHIEF: Well, I
VAN LUTYENS: It's important.
CHIEF: Check the feed valve.

[Control hall]

VAN LUTYENS: I've been looking at the installation plan, and the impeller intake valve in particular. I think I know where the blockage may be.
CHIEF: All right.
VAN LUTYENS: Well, this valve is at the base of the main shaft and leads directly to the intake, ja?
CHIEF: Mmm hmm.
VAN LUTYENS: Well, as far as I can see there is no point between that valve and the Control Rig where a blockage could occur big enough to stop the impeller.
CHIEF: Apart from the under-sea emergency valve.
VAN LUTYENS: But you've got remote control observation on those and they are free, ja?
CHIEF: Mmm.
VAN LUTYENS: So the impeller intake must be at fault.
CHIEF: It's possible.
VAN LUTYENS: Possible, man? It's the only answer. What we have to do is to go down and free that valve.
CHIEF: I'll have to check with Mister Robson.
VAN LUTYENS: Robson! Robson! What's the matter with you? Are you children? Can't you do anything on your own initiative?
CHIEF: Look, I can't send men down there without his approval.
VAN LUTYENS: Can you not also blow your nose without approval?
CHIEF: Now listen to me, Mister Van Lutyens. I've worked for Mister Robson a long time. We were out there on those rigs together in the early days. You may think he's wrong to run this place in the way he does, but I trust him. And I take orders from him purely because I trust his judgement. No other reason.
VAN LUTYENS: I'm sorry, Chief, I shouldn't have said that. You forgive me, ja? Now what I would like you to do is to go to Mister Robson and say we think we know where the blockage is, and get official permission to inspect the bass of the shaft.
CHIEF: Just a minute, that's your theory, that's not mine.
VAN LUTYENS: It's the only possibility. Anyway that sound you heard, it must have come from the bass of the shaft.
CHIEF: If the main valve is open it could be an echo from any one of those rigs.
VAN LUTYENS: If it is open! But you do not know that it is open and you will not know until you go down and check.
CHIEF: Well, I suppose I could put it to him.
(The heartbeat starts up again.)
VAN LUTYENS: You're not going to tell me that that is a mechanical fault.
CHIEF: I'll go and see him.
VAN LUTYENS: He's in his cabin.

[Refinery corridor]

ROBSON: Chief! What's the matter?
CHIEF: Mister Robson, that noise in the impeller, it's started again. I think we should go down and check the main valve, sir.
ROBSON: Oh, you do, do you?
CHIEF: Well, that's where we think the blockage is.
ROBSON: We?
CHIEF: Well, Mister van
ROBSON: Mister van Lutyens. Yes, I thought he'd get his nose in. Come on.

[Impeller room]

ROBSON: You lot get back to work. Mister Van Lutyens, I want to talk to you.
VAN LUTYENS: Mister Robson, there is something alive in the pipeline.
ROBSON: You're out of your mind. There's nothing down there.
CHIEF: I promise you, sir, I did hear something.
ROBSON: You've been unnerving my crew. Now you, get out!
VAN LUTYENS: Listen.
ROBSON: That's it. Did you hear what I said?
VAN LUTYENS: Now listen, will you? (heartbeats) It's down there, in the darkness, in the pipeline, waiting.

Episode Three

[Harrises' quarters]

(In the bedroom, Jamie bends down to examine the seaweed on the carpet.)
DOCTOR: No, Jamie, don't touch it.
JAMIE: But it's only a bit of seaweed.
DOCTOR: Yes, unless it really did move like Victoria said.
JAMIE: Oh, how can it move. It's not a living thing, is it?
DOCTOR: Everything in the sea is living, Jamie.
VICTORIA: Well, it did move. It gave me a shock. It was like a spider.
DOCTOR: Yes, well, we're not taking any chances. Hold that for me, will you?
JAMIE: What's this for?
DOCTOR: We're going to take a closer look at this weed. Now bring the bag down here. Right onto the floor. That's it. Now don't let it touch your fingers. Careful. Slowly does it. Mind your fingers. There.
JAMIE: What are you going to do with it?
DOCTOR: We're going to see if an ordinary piece of seaweed really can move.
HARRIS: Doctor, my wife, will she be all right?
DOCTOR: Oh, yes, I think so, yes. I don't think there's any panic, but I'd get her under medical supervision if I was you.
HARRIS: Yes, I'll go back to the Medicare centre at the compound and arrange for her to be taken in there.
DOCTOR: Yes, you do that.
(Harris leaves.)
VICTORIA: Poor man.
JAMIE: Aye. Hey! I thought we were supposed to be prisoners?
DOCTOR: Yes, so did I. We better make the most of it. We've got a lot of work to do back at the Tardis. She seems to be sleeping peacefully. Come on.
(The Doctor, Jamie and Victoria leave. Tendrils of seaweed start growing down Maggie's arms.)

[Impeller room]

CHIEF: What is it, that sound?
VAN LUTYENS: It's uncanny. It's like a heartbeat.
CHIEF: It's stopped again.
VAN LUTYENS: Well this is surely proof enough.
ROBSON: Proof?
VAN LUTYENS: There is something down there blocking the impeller.
ROBSON: Rubbish! Hysterical nonsense.
VAN LUTYENS: But you heard it, that dreadful sound.
ROBSON: I heard a fault in the base of the impeller.
VAN LUTYENS: But the impeller isn't working. Don't you believe a thing until you see it?
ROBSON: I want that pump operational in half an hour. Now get to it!

[Tardis laboratory]

(The Tardis has conveniently washed up on the beach. The Doctor gets Victoria to test a sample of the weed whilst he puts the rest in a glass tank.)
JAMIE: What are you doing, Doctor?
DOCTOR: Well you see, Jamie, these two cylinders contain a small amount of natural gas. It should be quite interesting to see what sort of effect it has on the weed. How are you doing, Victoria?
VICTORIA: I don't know, I think you ought to have a look.
DOCTOR: Oh yes, well, that's got the natural iron content.
VICTORIA: Well, I did the Bunsen test, like you told me, but I found something which worried me.
DOCTOR: Oh yes, I'm not surprised. Is this hot?
VICTORIA: No, no.
DOCTOR: You see this rusty stuff here.
VICTORIA: Yes?
DOCTOR: Well, it means that the weed's giving out a gas. Probably toxic.
VICTORIA: Toxic?
(Jamie is peering into a microscope.)
JAMIE: Hey, Doctor! What are these little wriggly things in the weed?
DOCTOR: Now just a minute, Jamie. I'm looking at. Little wriggly things? Where?
JAMIE: Here, look. Look in there.
DOCTOR: Jamie, this is it! There's molecular movement! Come and see, Victoria. There. Why, that's amazing!
JAMIE: What does it mean?
VICTORIA: It means, Jamie, that the weed is just as much alive as you and me.

[Refinery corridor]

VAN LUTYENS: Mister Harris, I've been trying to get hold of you. Mister Robson won't listen to reason.
HARRIS: I'm sorry, Van Lutyens, I've got something more important on my mind at the moment.
VAN LUTYENS: Important? What is more important?
HARRIS: My wife is ill. Get out of my way, man.

[Control hall]

HARRIS: Price!
PRICE: Yes, sir?
HARRIS: Is Doctor Patterson back?
PRICE: No, we've heard nothing from D Rig, sir.
HARRIS: Right. Get on to the Matron at the Medicare Unit and tell her to send a couple of orderlies over to my quarters with a stretcher to bring my wife in. She's ill. You know the extension.
PRICE: Yes, sir.
ROBSON: What's the panic now, Harris?
HARRIS: Go on, get on with it.
ROBSON: Harris, I asked you a question.
HARRIS: My wife is ill. She needs medical attention.
ROBSON: What's the matter with her, she got a hangover?
HARRIS: She's very ill, Mister Robson.
ROBSON: Who says so, that Doctor fellow? Incidentally, where is he and the two kids?
HARRIS: Oh, well, I left them in my quarters when I found my wife was ill.
ROBSON: You what? Those three prisoners were in your charge and you left them there?
HARRIS: I was worried about my wife. I didn't have time to think about it.
ROBSON: That's your trouble you never do think, do you, Harris, when you should. Those three prisoners were in your charge.
HARRIS: I don't care. Don't you understand? My wife was lying on the floor when I got there. She was unconscious and that smell of toxic gas was there. She's been poisoned, Robson, poisoned!
VAN LUTYENS: And this toxic gas, where does it come from?
HARRIS: Oh, I don't know.
ROBSON: And none of us will know now you've let them loose.
HARRIS: How could they possibly have anything to do with it?
ROBSON: That still doesn't alter the fact that you let those prisoners go without my authority.
HARRIS: Prisoners? A harmless old man and a couple of teenagers?
ROBSON: That harmless old man is probably a saboteur. It's probably him that's been tampering with that release valve on the shoreline. Creating all those variations in pressure you got so excited about!
HARRIS: Oh don't be so ridiculous, Robson. You're clutching at straws, stupidly blind to the real facts!
ROBSON: Don't shout at me, boy!
CHIEF: Mister Robson, sir. Mister Robson. The impeller, it's moving again.

[Impeller room]

ROBSON: Good man. I told you it was only a mechanical fault, didn't I.
CHIEF: It just started quite suddenly.
ROBSON: Keep it going, man.
CHIEF: I don't know if we can hold it.
ROBSON: Don't lose it now.
(The impeller stops again.)
ROBSON: You fools! You stupid fools!
CHIEF: Well, the faults not this end! It must be jammed at the base.
ROBSON: You wanted this, didn't you? It's just what you wanted!
VAN LUTYENS: You should have listened to me, Robson.
ROBSON: What, turned off the flow? Ruined a reputation of thirty years?
VAN LUTYENS: Reputation! Don't you realise that what is going on here is beyond your comprehension? That whatever it is that is in the pipelines, that's jamming the impeller, has taken over the rigs, is a menace and a threat to us all?
ROBSON: The only menace and threat around here is you, Van Lutyens. And you Harris. Listen. What are you staring at! I want that impeller working in half an hour. I'll be in my quarters. Let me know as soon as the impeller starts moving again.
(Robson leaves.)
VAN LUTYENS: Dwaas. He's cracking up, Harris.
HARRIS: Look. I've got to get back to my wife.
VAN LUTYENS: Harris, you can't go now. He's losing control.
HARRIS: My wife's been poisoned.
VAN LUTYENS: She's in good hands, ja? She'll be brought into the Medicare Unit. What can you do?
HARRIS: But I ought to go and see her.
VAN LUTYENS: To hang about and worry, that's all. Robson is cracking up. You are the only man with authority to take over. We need you here.
HARRIS: Chief.
CHIEF: Sir.
HARRIS: Mister Robson, you know him better than any of us. How do you? Do you think he's all right?
CHIEF: Well, he's under a lot of pressure, I think he's nerves are a bit.
VAN LUTYENS: Ja, pressure, strain. He's cracking up, I tell you.
CHIEF: Well, you're not helping him you know.
VAN LUTYENS: That's not my job. I am here to give technical advice which he ignores. All right, he knows a lot about engineering, but not all. And what he does not know is the state of mind of those men out there on the rigs.
CHIEF: He ought to know. He was out on those rigs himself long enough.
VAN LUTYENS: Oh, ja, ja. He has plenty of professional experience of normal conditions, but these are not normal conditions. There is something very strange going on here, but he refuses to accept the new factor.
CHIEF: So what do you think he should do?
VAN LUTYENS: I know what I would do. Close the compound, evacuate the rigs.
CHIEF: He'd never do it.
VAN LUTYENS: We have lost contact with two rigs. We have a major blockage in the main pipeline. The impeller is jammed, and we still don't know what is causing the trouble.
HARRIS: But we regained contact with Baxter on Rig D and he said everything was under control.
VAN LUTYENS: Ja, and we've not heard from him since. And what about Rig C?
CHIEF: Oh, that could be a telecommunications fault somewhere.
VAN LUTYENS: J., it could be, but we have to check that it is and we have to check the valve at the base of the impeller. But what does Robson do? Nothing! Nothing!
HARRIS: Well, I suppose he might listen if we all put it to him. What do you think, Chief?
CHIEF: You're absolutely right of course. We must check.

[Tardis laboratory]

(The Doctor shows Victoria a dusty book.)
VICTORIA: That's it, Doctor. That's the creature I saw back at the Compound.
DOCTOR: Yes. Yes, I was afraid it would be.
VICTORIA: But how did it get in this book?
DOCTOR: Well, I told you, Victoria, this is a book of legends and superstitions. This particular drawing was supplied by ancient mariners in the North Sea in the middle of the eighteenth century, Jamie.
JAMIE: That's my time. You mean to say this is the creature that Victoria saw back at the Compound.
DOCTOR: Yes I think there's no doubt about it.
JAMIE: Well, what about these great clumps of weed.
DOCTOR: Well there's obviously some connection between the weed and the creatures themselves.
(Jamie starts to sneeze.)
VICTORIA: Oh, no!
DOCTOR: Gas!
VICTORIA: What?
DOCTOR: Jamie! Jamie, help me get the lid on! Oh, no. Quickly!
(The seaweed has been growing in the tank and is about to slither out. Victoria screams. The weed creature falls back in and the Doctor and Jamie firmly shut the lid.)
DOCTOR: I was right. The weed formations are feeding off the natural gas beneath the North Sea and giving off toxic gas. Come on. We must get back to Harrises' quarters. Come along. Just a minute. That weed went back in its tank very suddenly, didn't it? I wonder why? Never mind.

[Control hall]

ROBSON: No, I will not listen. It's you, Van Lutyens, isn't it? Isn't it? You've been undermining my authority ever since you came here. You and Harris. You've been stirring up trouble just to get at me, haven't you? You've even got the Chief on your side now. One of my oldest and trusted friends.
CHIEF: Mister Robson.
ROBSON: At least I thought I could trust you.
CHIEF: Mister Robson, all we want to do is
ROBSON: I know what you want! I know what you all want! You're going to get at me, just so I'll give up. I'm not going to give you that pleasure! Why don't you go and join him? Go on, join Van Lutyens! Go on, join him! What are you standing around for? What are you starring at? I'm in charge! I'm in charge here!
(Robson leaves as Harris enters.)
HARRIS: Mister Robson.
ROBSON: I'm in charge of this Compound, Harris! It's my responsibility! Mine! My responsibility!
(Robson finally leaves.)
VAN LUTYENS: Do you still think he's capable of running this place? You do what you like. I'm going to get in touch with my people in the Hague.
HARRIS: What can they do?
VAN LUTYENS: I don't know. They might push your people in London into some sort of action. Give me a direct line to Van der Post, Hague Central,
PRICE: Yes, sir.

[Robson's cabin]

(Robson slams the door then slumps down on his bunk, exhausted. Outside, Mister Oak comes down the corridor and locks Robson's door.)
ROBSON: Who's there? Go away. I'm not to be disturbed.
(Mister Oak operates the emergency vent controls for the cabin. Robson becomes aware of a hissing sound and the smell of gas. He sits up to see foam coming through the ventilation grille. Tendrils of weed come towards him. He shouts out.)

[Outside Robson's cabin]

HARRIS: Mister Robson?
(Harris unlocks the door and Robson bursts out, staggering down the corridor.)
HARRIS: Mister Robson, wait! I need your permission to send two men down the impeller shaft to
(Robson has gone. Harris goes into the cabin and sees the tentacles coming out of the foam. He flees.)

[Harrises' quarters]

(Victoria uses a hairpin to unlock the door.)
DOCTOR: Well, thank you, Victoria. Yes, nobody here. It's better that way.
JAMIE: You speak for yourself. I'd rather
VICTORIA: Oh no!
(Jamie sneezes.)
DOCTOR: Gas!
VICTORIA: Where's it coming from?
DOCTOR: Jamie, try the kitchen.
(The Doctor and Victoria go to the bedroom and face a mass of foam coming towards them. A weed tentacle lashes out. Victoria screams and it pauses then retreats.)
VICTORIA: What's it doing?
(They see that the bed is empty.)
DOCTOR: We've apparently frightened it away.
VICTORIA: Mrs Harris?
DOCTOR: Mrs Harris. Ah. Oh yes, of course. Mister Harris had her taken over to the Medical centre. At least I hope he did.
JAMIE [OC]: Doctor, quick, help me!
DOCTOR: That's Jamie!
VICTORIA: Jamie!
JAMIE [OC]: Doctor, I'm in here.
(The Doctor bursts into the kitchen but there is a wall of foam in front of him. He slams the door shut again.)
JAMIE [OC]: I can't hold out much longer.
VICTORIA: Now what?
DOCTOR: The terrace!
(The Doctor and Victoria go through the study to the patio. Through the kitchen window they see Jamie standing on the kitchen table, surrounded by a rising tide of foam and tentacle.)
DOCTOR: Jamie! Victoria, come on, follow me.
VICTORIA: What are we going to do?
JAMIE [OC]: Quick, Doctor. Hurry.
(There's an external metal staircase to the roof. The Doctor and Victoria climb to the kitchen skylight and open it.)
DOCTOR: Give me a hand!
(They pull Jamie up and out to safety.)
DOCTOR: Come on, out you come, Jamie.
(The foam fills the kitchen as they scramble away, then comes out onto the roof.)
DOCTOR: Pass him down, Victoria.

[Robson's quarters]

HARRIS: Yes, it's in here. Look. Well, it was in here. I saw it.
VAN LUTYENS: You did?
HARRIS: Yes, it was moving. Something alive. You don't believe me.
VAN LUTYENS: Oh yes, I believe you, Mister Harris. It must have come out of the ventilator grille, like it did in the oxygen store.
HARRIS: You mean when that girl Victoria was locked in.
VAN LUTYENS: Ja. And having achieved its purpose, back down the shaft.
HARRIS: Purpose? What purpose?
VAN LUTYENS: Who knows? We know so little about it. And no one tries to find out.
HARRIS: I know.
VAN LUTYENS: Least of all Robson.
HARRIS: Yes, he rushed out of here as though he were, he was out of his mind.
VAN LUTYENS: You'd better alert security. He may do himself some harm.
HARRIS: Yes, you're right.

[Outside Robson's quarters]

(Harris locks the door.)
HARRIS: At least the stuff won't get out of here.
VAN LUTYENS: Oh really, Mister Harris. There must be hundreds of grills in this compound. And once the foam has got into the shaft it could emerge from any one of them.
HARRIS: I suppose you're right. Then we must insist that all emergency ventilators are kept shut.
VAN LUTYENS: Mister Harris, you know what you must do now?
HARRIS: Do?
VAN LUTYENS: Assert yourself. Take over the compound.

[Control hall]

HARRIS: Price.
PRICE: Yes, sir.
HARRIS: I want you to alert the security posts. Mister Robson may be ill. I'd like to know his whereabouts.
PRICE: Very good, sir.
HARRIS: And order all areas to keep their emergency air vents closed. Understand?
PRICE: Yes, sir.
VAN LUTYENS: You're taking over then?
HARRIS: Robson is still officially in charge.
VAN LUTYENS: I've already informed my authorities at the Hague. You must do the same with your Director in London.
HARRIS: Yes. Price?
PRICE: Yes, sir.
HARRIS: Get me Board Headquarters. I want to speak to Megan Jones.

[Refinery corridor]

DOCTOR: Are you all right, Jamie?
JAMIE: Oh, I've come over dizzy.
DOCTOR: Well, you just rest a while.
JAMIE: I'll just get my breath back.
VICTORIA: Doctor, why is it that we always land up in trouble?
DOCTOR: Well, Victoria, it's the spice of life, my dear.
VICTORIA: Oh, well I'm not so sure. I don't really like been scared out of my wits every second.
DOCTOR: Is something wrong?
VICTORIA: Well, I just wish that once. Oh, never mind.
DOCTOR: Are you right, Jamie? Come on then.
JAMIE: What's the matter with Victoria?

[Control hall]

PRICE: Thank you, Miss Jones. We'll see you then in three hours time. Goodbye.
HARRIS: In three hours the whole compound will be crawling with board officials.
VAN LUTYENS: Let's hope the situation doesn't get any worse.
HARRIS: I only hope Megan Jones understands why I've taken over. It was she who insisted that Robson should know this particular complex in the early days.
VAN LUTYENS: You did right. I will stand by you. You couldn't let Robson go on. You had the men on the rigs to think of. They are now her responsibility.
HARRIS: If only we knew what we were up against. These creatures that have been getting into the refinery, where do they come from? We don't even know what they are?
DOCTOR: That's where you're wrong, Mister Harris. We do know what they are. At least I think we do. Seaweed!
HARRIS: Seaweed?
DOCTOR: Yes. Not the sort that you'd normally find on the beach. This seaweed happens to be dangerously alive.
HARRIS: Alive? But how can it be?
DOCTOR: I think you better listen to me. I think you'd all better listen to me. Large formations of seaweed have been coming up on the beaches along this coast. Seaweed that shows clear indications of having life like human beings.
CHIEF: It's this seaweed that's blocking the pipeline then.
DOCTOR: Yes, I think there's no doubt about it.
VAN LUTYENS: We must clear the base of the impeller.
DOCTOR: No, wait. The weed is capable of protecting itself. It gives off a toxic gas. It's also a parasite. It attaches itself to other living things.
HARRIS: You mean human beings? But what happens to them?
DOCTOR: I'm afraid I don't know.
HARRIS: But my wife was stung by the seaweed.
DOCTOR: Ah, yes, but she survived, didn't she? How is she?
HARRIS: Well I asked the Medicare Centre to bring her in. Price? Get Medicare for me and ask how my wife is now. Doctor, I've just seen one these creature things that your young friend saw in the Oxygen room.
DOCTOR: Oh? Where?
HARRIS: In Mister Robson's cabin. It might have attacked him. He was in a wild state when I went in and just run out. He hasn't been seen since.
DOCTOR: Oh dear.
PRICE: Mister Harris, sir.
HARRIS: Yes?
PRICE: The Matron says she's sorry, she hasn't brought your wife in yet but she's sending someone over now.
DOCTOR: What?
HARRIS: What is it, Doctor?
DOCTOR: Well, we've just come from your quarters. Your wife wasn't there!
JAMIE: The place was covered with seaweed.
HARRIS: Is this right?
DOCTOR: Yes, yes, I'm afraid it is.
HARRIS: Then where is she? Where is she? I must go and find her.
(Harris leaves.)
VAN LUTYENS: Wait! Well, where do you think she is? Do you think it has anything to do with this seaweed stuff?
DOCTOR: I don't know. I simply don't know.

[Beach]

(Maggie is staring out to sea. Her neck and face are covered with fronds of weed. Robson comes up and stands next to her.)
MAGGIE: There is little time. You know what you must do?
ROBSON: Yes.
MAGGIE: You will obey?
(Robson nods, then watches Maggie walk into the sea until the waves break over her head.)

Episode Four

[Control hall]

PRICE: Rig D. Rig D. Control calling Rig D. Come in, please. Rig D. Rig D. Control calling. Come in, please. I'm sorry, sir. I can't reach them.
VAN LUTYENS: Try Rig A again.
PRICE: Rig A. Control calling Rig A. It's no good, sir. That's three rigs not answering now, sir.
VAN LUTYENS: The men on the remaining rigs won't last under suspense much longer. Try the guard post again. See if there's any sign of Mister Harris.
PRICE: Very good.
VAN LUTYENS: Three Rigs now. What can have happened to them?
DOCTOR: Well, can't you send someone out to investigate?
VAN LUTYENS: No, I'm afraid I have no authority here. I'm just here as technical adviser. Mister Harris is in charge. When he comes back he might possibly authorise the company helicopter for at least to take a look.
DOCTOR: We can do nothing.
VAN LUTYENS: Nothing. Wait. Wait.

[Impeller room]

CHIEF: Nothing. Keep checking.
(A heartbeat sound becomes audible. The tired men become afraid.)
CHIEF: That's started again.

[Bunk room]

VICTORIA: Jamie. Jamie? Jamie, you asleep?
JAMIE: I'm just resting my eyes.
VICTORIA: I don't know how you can with all this trouble going on.
JAMIE: Oh, don't worry. The Doctor will work something out. He always does.
VICTORIA: Yes. What then?
JAMIE: What do you mean, what then?
VICTORIA: Where will we be next?
JAMIE: Oh, Victoria, you know better than to ask a question like that. We never know where we're going to land one place to the next. It's half the fun, isn't it?
VICTORIA: Is it?
JAMIE: Victoria, what's the matter? You've been acting very oddly ever since we got here.
VICTORIA: Oh it's nothing. It doesn't matter.
JAMIE: Look you'll worry the Doctor if
VICTORIA: Jamie, I said it was nothing. Just go back to sleep.
JAMIE: Aye. Well I wouldn't worry about that old bit of sea weed. The Doctor'll work something out.
VICTORIA: Yes, but will he? There's so many questions. The weed grows. Feeds off natural gas. But how fast does it grow? What happens to those that touch it? Oh, Jamie. Jamie, I'm frightened!
(The Doctor enters.)
DOCTOR: Oh, I'm sorry, Victoria. Did I startle you?
VICTORIA: Yes.
DOCTOR: Where's Jamie?
VICTORIA: Up there. He's still asleep. Nothing would wake him except a bomb dropping.
DOCTOR: Oh good.
VICTORIA: Doctor, what's happening?
DOCTOR: Well, I'm not sure, Victoria. I'm not sure. Looks so peaceful out there, doesn't it?
VICTORIA: I heard that noise again.
DOCTOR: Yes.
VICTORIA: Well, what are they doing about it?
DOCTOR: Well, we have to wait.
VICTORIA: Wait? But what for? For one of those awful creatures to come and attack us all?
DOCTOR: Now, Victoria, it's not as bad as all that, you know.
VICTORIA: Isn't it? Even you don't know really how bad is it, do you?
DOCTOR: Well, no, not exactly.
VICTORIA: Every time we go anywhere something awful happens. Daleks. Cybermen.
DOCTOR: Yeti?
VICTORIA: Yes, and Yeti. Why can't we go anywhere pleasant, where there's no fighting. Just peace and happiness.

[Beach]

HARRIS: Mister Robson! Mister Robson! Robson! Robson! Mister Robson! Mister Robson! What are you doing down here, sir? Have you seen my wife at all?
ROBSON: Your wife?
HARRIS: I've been searching for her.
ROBSON: You'll find her, Mister Harris. Very soon.
HARRIS: Then you haven't seen her?
(Robson turns and walks off along the beach.)
HARRIS: Robson!

[Impeller room]

DOCTOR: If you don't mind my saying so, Mister Van Lutyens, I think this is a very bad idea of yours. You don't know what you're up against.
JAMIE: Aye, you wouldn't catch me down there.
CHIEF: Why don't we wait until Mister Harris comes back, sir?
VAN LUTYENS: The only way to find out if this weed stuff of yours is blocking the base of the impeller is to go down and have a look.
CHIEF: Look, Mister Van Lutyens, I have no authority to send my men down there.
VAN LUTYENS: I realise that. That is why I am going down.
CHIEF: By yourself?
VAN LUTYENS: Oh yes.
CHIEF: I wouldn't go down. Well, I hope you know what you're doing, sir.
VAN LUTYENS: I think so.
DOCTOR: I wish you wouldn't do this, Mister Van Lutyens.
VAN LUTYENS: I can't sit about waiting any longer. I have no position of authority here but I do have the run of the company installations, and if I can do nothing else I can at least inspect the base of the impeller shaft.
(Van Lutyens puts on a gas mask and steps through the airlock onto the impeller shaft lift platform.)
VAN LUTYENS: Tot straks.
DOCTOR: Good luck.
JAMIE: Aye, you'll need it.
CHIEF: All right, lower him down.
(Oak and Quill are at the lift controls.)

[Impeller shaft]

(At the bottom, Van Lutyens switches on his torch and steps out of the lift. He goes to a hatch in the floor, opens it and looks down into the pipeline chamber. The heartbeat can be heard in the pipes. Suddenly Van Lutyens realises that the pipeline is full of foam and seaweed. It surges up to engulf him and he cries out as the weed grabs hold and pulls him down into the pipe.)

[Impeller room]

CHIEF: Get him up!
VICTORIA : What is it? What's happened?
JAMIE : Van Lutyens is down there.
VICTORIA: What's happened to him?
DOCTOR: Well, we don't know, Victoria.
(The lift comes up.)
DOCTOR: What's happened? What did you see?
CHIEF: He's not in the shaft. He must still be down there. Let's find Mister Harris.
DOCTOR: We can't just leave him down there.
JAMIE: What are we going to do?
DOCTOR: We're going down there after him.
VICTORIA: Oh, Doctor, no.
JAMIE: Oh no, we're not.
DOCTOR: Jamie, you wouldn't let me go down there on my own, now would you?
JAMIE: Er, well, no. Oh.
VICTORIA: Oh Doctor, you can't. You don't know what's down there.
DOCTOR: Open the airlock.

[Control hall]

PRICE: Miss Megan Jones? Just leaving the reception now. Right. Thank you. Ah, Mister Harris. Mister Harris, we've been looking for you everywhere.
HARRIS: What is it, Price?
PRICE: Are you all right, sir?
HARRIS: Yes. Just tired. Is there any news of my wife?
PRICE: No, I'm afraid not, sir. You didn't find her? Oh, Mister Harris?
HARRIS: Yes?
PRICE: The director, Miss Megan Jones, is leaving reception on her way here now, sir.
HARRIS: I see. Thank you, Price. Where's Mister Van Lutyens?
PRICE: In the Impeller area I think, sir.
HARRIS: All right.

[Impeller room]

CHIEF: This is terrible. Do you mean to say they both went down inside that shaft?
VICTORIA: I couldn't stop them. They went to look for Mister Van Lutyens.
HARRIS: What? What has happened to him?
(Oak and Quill are still at the lift controls as Harris enters.)
CHIEF: Mister Harris, thank goodness you're back. Mister Van Lutyens went down inside the impeller shaft to try and find what was blocking the pipe line.
HARRIS: Yes?
CHIEF: He didn't come back. Now the Doctor and the boy has gone down there.
HARRIS: They've done what? Get them up at once. Stop the lift.
OAK: I'm sorry, sir. It's too late.

[Impeller shaft]

(The Doctor and Jamie are both wearing gas masks.)
JAMIE: Gloomy sort of place, isn't it?
DOCTOR: Jamie, that hole goes straight down to the big gasometer down below.
JAMIE: Hey, isn't that Van Lutyens' torch?
DOCTOR: Well, it must be.
JAMIE: But where is he?
DOCTOR: Shine it down there, Jamie.
(The torch doesn't work.) 
DOCTOR: Give it to me.
JAMIE: Come on, Doctor. Let's get out of here. You can feel there's something evil lurking down here.

[Refinery corridor]

PERKINS: It all seems quiet enough, Miss Jones.
JONES: Of course it is. Robson's an efficient man. Why do you think I gave him control of the compound? He knows the job backwards.
PERKINS: Then why the sudden panic?
JONES: I don't know. Harris was rather vague.
PERKINS: Vague? He said he was taking over from Robson. I wouldn't call that vague.
JONES: You've never met Robson, have you Perkins?
PERKINS: No. But I've
JONES: When you do, you'll realise he's not the sort of man one pushes around.
PERKINS: Then what's it all about?
JONES: Just an internal squabble, I'd say. Harris is a bright man. I sent him thinking he might gain from Robson's practical experience. Obviously the two haven't hit it off together.
PERKINS: So we're pouring oil. Politics?
JONES: Let's go and see, shall we?

[Impeller room]

VICTORIA: Jamie! Doctor! Oh, I do wish they'd hurry.
HARRIS: Is there any way we can get them up, Chief?
CHIEF: Well, we can't use the lift in case they want to get back in a hurry. There is the ladder inside the pipe line.
PRICE: Mister Harris?
HARRIS: Yes, what is it, Price?
PRICE: Miss Megan Jones has arrived, sir.
HARRIS: Oh, I see. Thank you. Chief, you'd better come with me. I'm going to need some support when I talk to Megan Jones.
CHIEF: All right.
VICTORIA: But what about Jamie and the Doctor?
HARRIS: There's isn't a great deal we can do at the moment, I'm afraid. Oak, as soon as they signal, bring them up. And if there's any sign of trouble, come and get me.
OAK: You can rely on us.
HARRIS: Come on, Chief.
VICTORIA: Will they be all right. I mean, is it safe?
OAK: Oh yes, Miss. Don't you worry about a thing. We'll take care of everything won't we, Mister Quill?

[Control hall]

JONES: Creatures? Seaweed creatures? What do you say to that, Perkins?
PERKINS: Oh, well
HARRIS: It's true.
JONES: You can't be serious, Mister Harris.
HARRIS: These creatures have been seen in the refinery itself, in the oxygen room
JONES: By some half-witted Doctor and a couple of teenagers.
HARRIS: And by me.
JONES: You've seen them?
HARRIS: Yes, Miss Jones. I have seen them.
JONES: Harris, I understand your wife had some sort of accident. I know this must have been a considerable shock to you and I fully understand
HARRIS: You think I'm lying, that I've been seeing things? Believe me, there are things you don't know.
JONES: I know throughout the southern region receiving stations are working on emergency supplies. What are we going to do about it?
HARRIS: At present there's nothing we can do about it. One by one we're losing contact with the rigs out at sea.
JONES: Then I suggest you send someone out there to see what's going on.
HARRIS: All right. Have I your permission to call out Air Defence.
JONES: Certainly not. This not is a national emergency. Use the company helicopters.
HARRIS: But you don't understand what's going on.
JONES: Will you please do as I say.
HARRIS: Price?
PRICE: Yes, sir.
HARRIS: Get me the helicopter hangar, please.
PRICE: Very good, sir.
JONES: Now, Mister Harris, I think I'll have a talk with Chief Robson.
HARRIS: Oh, I'm sorry, I think. Well, he's not very well.
JONES: Not well? In what way?
HARRIS: Something's happened to him. That's all I can tell you.
JONES: Well, what? What's happened?
HARRIS: I don't know. I just don't know.

[Impeller shaft]

JAMIE: Can you see anything?
DOCTOR: No, it's too dark, Jamie. Not a sign of Van Lutyens.
JAMIE: Well, no point in hanging about here.
DOCTOR: Wait a minute.
(There's that bubbling sound.)
DOCTOR: Come on, Jamie. Let's get out of here. Press the lift button!
(Up in the impeller room, an alarm sounds but the room is empty.

[Control hall]

PRICE: HQ calling Rig D. This is Feed HQ calling Rig D. Come in, please. Can you hear me?
HARRIS: It's no use, there won't be a reply.
JONES: Don't be a fool, man. We must keep trying. If there are men out on those rigs there must be a reply.
HARRIS: If? But we don't know. We've already lost contact with three of our drilling rigs.
PERKINS: And you say there is definitely something down there in the impeller shaft blocking the flow?
JONES: You've checked the impeller?
HARRIS: Chief?
CHIEF: It's not the impeller. I've checked every last nut and bolt. Whatever it is, it's down there in that shaft.

[Impeller shaft]

(Jamie and the Doctor are on the lift platform as the foam gets ever closer.)
JAMIE: Get us out of here!
DOCTOR: Take the lift up!
(They can just see weed creatures rising up, tentacles reaching for them. Then the Doctor spots the maintenance ladder in the wall of the shaft and they head for it.)

[Impeller room]

(Oak and Quill enter from the pipeline room and lock the door, then go out into the corridor. The emergency light is still flashing and alarm sounding. Then the Doctor emerges breathless from the shaft.)
DOCTOR: Give me your hand.
JAMIE: You all right?
DOCTOR: Yes, I think so.
JAMIE: What a climb.
DOCTOR: It's the weed. It must fill the entire shaft. It was moving pretty quick, too.
JAMIE: Let's get out of this in case, then. Where's Victoria?
DOCTOR: I don't know.
(The Doctor shuts off the alarm.)
DOCTOR: No wonder they didn't see the lift shaft signal. There's no one here.
JAMIE: Victoria wouldn't desert us.
DOCTOR: No. Not unless she'd been persuaded to. Jamie, I think we'd better go and look for her. Come on. You go that way. I'll go this way.
JAMIE: Right.

[Control hall]

JONES: Foam and weed on all the rigs?
HARRIS: According to the helicopter pilot. And no sign of life at all.
JONES: It's so fantastic. What on earth are we going to do?
HARRIS: Save the lives of the men on all the other rigs.
JONES: How?
HARRIS: Give me permission to evacuate them.
PERKINS: What?
HARRIS: And then blow every one of the rigs to pieces, right out of the sea.
PERKINS: You must be out of your mind. Miss Jones, you can't really agree to such a thing.
HARRIS: We have to. The men's lives are more important than any of those rigs.
PERKINS: The Minister would never agree.
JONES: That'll do, Perkins. You ask me to destroy years of hard work, skill and government money like that?
HARRIS: I'm asking you to destroy this evil that's in the sea before it's too late. Bomb the rigs. I implore you.
ROBSON: No! No! Never! You leave those rigs alone. They're mine. They're mine, I tell you. Mine.
JONES: Robson, what's the matter with you?
ROBSON: Can't you see? They're getting at me. Those rigs, they're mine. I built them. My own flesh and blood. They're mine. They're my life! They want to destroy everything. They think in that way they can destroy me. We won't allow it.
JONES: We? Who, Robson, who?
ROBSON: My. I don't know. Chief. Chief.
JONES: Are you all right, Robson?
ROBSON: Yes, I'm all right. I don't know. I don't know if
JONES: Robson.
HARRIS: Let him go. The strain must have affected his mind.
DOCTOR: Oh, it's not that, I can assure you.
HARRIS: Doctor.
JONES: And who are you?
DOCTOR: Well, I
HARRIS: Doctor, I've almost forgotten. What about Van Lutyens? Did you?
DOCTOR: I'm afraid not.
HARRIS: Have you any idea what happened?
DOCTOR: Yes. Jamie and I nearly joined him. The whole of the bottom of the impeller shaft is covered in weed and foam.
JONES: What happened to Mister Van Lutyens? And Mister Robson?
DOCTOR: I'm afraid that Mister Robson is being controlled by some force that emanates from this weed.
JONES: That's incredible.
HARRIS: That's what we've said so far about everything the Doctor has told us. Each time he's been proved right. I think it's about time we started to believe him.
JONES: All right. The least I can do is listen.

[Refinery corridor]

JAMIE: Victoria. Victoria, it's me, Jamie. Where are you? Victoria!

[Control hall]

JONES: You think this seaweed or what ever it is, is a living organism capable of exercising telepathic control?
DOCTOR: Yes.
JONES: But seaweed's a vegetable matter. Everyone knows that.
DOCTOR: This is a struggle for power, Miss Jones. Matter over mind. I'm convinced all these people Mrs Harris, Chief Robson, Mister Van Lutyens, have all been overcome in this struggle and goodness knows how many more people.
HARRIS: But where does the weed get this intelligence from, Doctor?
DOCTOR: From the human brain. It's parasitic.
HARRIS: You mean the creatures have taken over human beings?
DOCTOR: I don't know, but they've certainly become part of the colony.
PRICE: Mister Harris? Control rig.
BAXTER [on monitor]: Hurry. Hurry. Emergency.
HARRIS: Control. Yes, Baxter, what is it?
BAXTER [on monitor]: At last. Mister Harris, for pity's sake, they're all around us.
HARRIS: What is, Chief? What's happening?
BAXTER [on monitor]: These things, they're everywhere. They're all over every thing, in every place. Mister Harris
HARRIS: Baxter! Baxter! Can you hear us?
BAXTER [on monitor]: Argh! Get us out of here! Somebody get us out of here!
(The screen goes blank.)
PRICE: Feed HQ calling Control rig. Come in please. Come in please.

[Impeller room]

JAMIE: Victoria? Victoria? Victoria? Back to square one. She must be somewhere.
(Jamie looks through the window into the pipeline room. He sees Victoria lying on the steps by the gas pipe.)
JAMIE: Victoria!
(The door is locked. Jamie finds a key lying around and tries it.)

[Pipeline room]

JAMIE: Victoria. Victoria. Say something. No. No, you can't be dead. Victoria, if anything happened to you, I'd never forgive myself.
VICTORIA: Oh Jamie, I didn't know you cared.
JAMIE: Victoria Waterfield! You tricked me! That's not fair.
VICTORIA: I did not. I was unconscious.
JAMIE: Aye? What happened?
VICTORIA: Those two engineers, they must have
JAMIE: What engineers?
VICTORIA: You know, the, the, and the little one.
JAMIE: You mean the two that were with the swing
VICTORIA: Yes. Yes, that's right. Oh, I don't remember. I must have passed out.
JAMIE: If I ever get my hands on them. You know the Doctor and me, we were nearly. Aye, well, never mind about that.
VICTORIA: Oh Jamie, why are we always getting into trouble like this? It's the same everywhere we go.
JAMIE: How do you mean?
VICTORIA: I don't know. I'm just fed up. I'm tired of one crisis on top of another. I just want some piece and quiet.
JAMIE: But, Victoria, are you not happy with the Doctor and myself?
VICTORIA: Oh yes, yes, I am. But I just.
JAMIE: What's the matter?
VICTORIA: Listen.
JAMIE: Hey, what's the matter?
VICTORIA: Listen, Jamie.
JAMIE: What is it?
VICTORIA: Can't you hear it? It's that noise again.
JAMIE: Yes but where's it coming from? Victoria, look!
(The transparent panel in the pipe is full of foam.)

[Control hall]

DOCTOR: With the Control rig gone, we can draw only once conclusion. The weed is trying to take over all the rigs and form one vast colony.
JONES: With what objective?
DOCTOR: The saturation of the British Islands and perhaps in time the entire planet.
PERKINS: Is such a thing possible?
DOCTOR: Oh yes. Unless we can find the nerve centre and destroy it.
JONES: But how can we possibly do that? It could be anywhere out there in the North Sea.
DOCTOR: Yes, that is the difficulty.
JAMIE: Doctor!
DOCTOR: What is it?
JAMIE: Doctor, the pipeline. Quick.
VICTORIA: Quickly, come and see.
DOCTOR: All right. What's happened?
JAMIE: It's here. It's come up.

[Pipeline room]

JONES: What in heaven's name is that?
DOCTOR: The advance guard.
JONES: I don't understand. What's happening?
DOCTOR: The first part of the invasion.
VICTORIA: Doctor, don't go near.
DOCTOR: It's begun. The battle of the giants.

Episode Five

[Control hall]

PRICE: Feed HQ calling Rig F. Feed HQ calling Rig F, can you hear me? Come in, please. Oh, Mister Harris? Mister Harris, I can't raise any of the rigs. Not one.
HARRIS: This is unbelievable!
PRICE: I'll try again, sir. Feed HQ calling Rig B. Feed HQ calling Rig B, can you hear me?
JONES: Well, keep trying, man.
DOCTOR: Your wasting your time, Miss Jones. By now all those rigs will have been taken over by the weed colony.
HARRIS: I don't care about the rigs. What's happened to the crews?
DOCTOR: The worst, I'm afraid.
HARRIS: Then we've got to destroy the rigs.
JONES: No!
DOCTOR: No, we daren't do that .
HARRIS: Why not?
DOCTOR: Well, that would spread this menace over a wide area and make it impossible to attack it.
HARRIS: Well, what are we going to do?
DOCTOR: No, what is the weed going to do?
JONES: What can it do?
DOCTOR: Well, let's think. Now I imagine that in the first place the weed was drawn up by one of the drilling rigs.
HARRIS: No, no. Anything that comes up through the bores would be cleared by the engineers at the source otherwise it would block the pumps.
DOCTOR: Precisely. And the engineers who cleared it must have touched it, yes?
HARRIS: Yes, so they must have been amongst the first to be controlled.
DOCTOR: And since then, this attack, and it is an attack, has followed a set pattern.
JONES: How do you mean?
DOCTOR: Top priority people have been attacked first.
JONES: If your theory is correct, the weed now controls two people who know the entire layout and structure of this whole compound.
DOCTOR: Yes, I'm very much afraid that is true.
JONES: Robson was here not long ago. We must find him and prevent them using him, for his own sake as well as ours.
HARRIS: Yes I agree. Price?
PRICE: Sir.
HARRIS: Get security to search the entire compound. I want Mister Robson found and put under armed guard in his cabin.
PRICE: Very good, sir.
HARRIS: Doctor, there's one thing that doesn't fit in with your theory.
DOCTOR: Oh, and what's that?
HARRIS: When Victoria was locked in the Oxygen room. Now she's nothing to do with the personnel here.
DOCTOR: Yes, that's something that's been puzzling me too. But she disturbed somebody who was interfering with the oxygen supplies.
HARRIS: Someone wearing a gas mask.
DOCTOR: Now supposing that person was under the control of the weed, he was wearing a gas mask for one reason only.
HARRIS: Because to him pure oxygen would be toxic?
DOCTOR: Exactly, Mister Harris.
HARRIS: Well then, we can use the oxygen as a weapon against the weed.
DOCTOR: Well, it's only a theory at the moment.
JONES: Well as Mister Harris said before, you've been right so far. There's no reason why you shouldn't be now.
(Oak and Quill leave.)
DOCTOR: Oh, how nice to be trusted. But I only hope I am right.

[Oxygen room]

(Outside the Oxygen store room, Oak and Quill put on gas masks, then enter.)

[Control hall]

PRICE: Good. See that he stays there. Mister Harris?
HARRIS: Yes?
PRICE: They've found Mister Robson.
HARRIS: Good. Where?
PRICE: In his cabin, lying on his bunk, apparently.
HARRIS: Oh well that's a relief.
PRICE: There's a guard at the door, sir.
HARRIS: Good.
JONES: Mister Harris. I want to see Mister Robson.
HARRIS: Robson? But he's ill. He won't be able to put two
JONES: I want to see him.
HARRIS: But you've seen him already. Surely you could see he was in no fit state to help us in any way.
JONES: I fully realise that, Mister Harris, but we're old friends. He might talk to me. There's just a possibility that he may know something that could help us.
HARRIS: I see. All right, but I'm coming with you. Robson's in an unpredictable state at the moment. He could be violent.
JONES: All right. You come too, Perkins.
PERKINS: Yes, Miss Jones.
(Jones and Perkins leave.)
HARRIS: Oh, if anything happens, Price, anything at all, I'll be with Miss Jones in Mister Robson's cabin.
PRICE: Very good, sir.
HARRIS: Chief.
CHIEF: Right, sir.

[Corridor]

PERKINS: Look, why don't you get the Minister to call up the National Defences?
JONES: What exactly do you suppose the armed forces could do?
PERKINS: Well, attack this weed or whatever it is.
JONES: How? If we attack the rigs what about the men out there?
PERKINS: But we don't know that they are there.
JONES: Equally we don't know that they aren't. They could be prisoners, anything. And anyway, even if we blow the rigs out of the sea there's no guarantee it will end this nightmare. It might well spread the menace as the Doctor suggested.
HARRIS: This way please, Miss Jones.
JONES: Right. And come along, Perkins. Don't look so worried, man. You might as well go home. Oh, I'm sorry. Come on.

[Outside Robson's cabin]

JONES: If you please, Harris.
HARRIS: Miss Jones, I'd rather you let me or Perkins come in with you.
JONES: No. Now don't fuss, Harris. I'll be perfectly all right.

[Robson's cabin]

(Robson is lying on his bunk, staring at the ceiling.)
JONES: Robson. Robson! John. John? It's all right. John, it's me Megan, Megan Jones.
ROBSON: Megan.
JONES: I want to try to help you.
ROBSON: Can't help. No one can help.
JONES: John, can you tell us what happened?
ROBSON: No.
JONES: John, listen to me. We can't help you unless you help us.
ROBSON: Can't help. No one can help.
JONES: Yes, we can, John, if you let us. Now whatever it is that's affecting you, you've got to fight it.
ROBSON: Can't fight.
JONES: You've got to fight it, John.
ROBSON: Can't fight it.
JONES: Now come on, Robson. Robson! Now listen to me. I'm director of the board. I put you in charge of this area and I can just as easily send you back to the rigs. Do you understand me, Robson? Now pull yourself together, man!
ROBSON: Megan, I
JONES: Pull yourself together!
ROBSON: Megan. Megan, help me. Help. Help me, Megan!
JONES: John.
ROBSON: Help!
JONES: It's all right, John.
(Harris and Perkins enter.)
HARRIS: Miss Jones?
JONES: John, can you hear me? Can you hear me? It's as if he was in a trance. Hypnotised. I thought for a minute he was rational.
HARRIS: I think we'd better let him rest.

[Outside Robson's cabin]

JONES: Harris, is there nothing we can do to help him?
HARRIS: No, the Doctor couldn't help my wife so I'm sure there is nothing he can
JONES: No. No, of course not. As far as I can see the only thing to do is to destroy this weed. Come on.

[Control hall]

(The Doctor is thinking.)
JAMIE: He does look worried this time. It's beginning to give me the willies.
VICTORIA: Yes. I wish we could go back to the Tardis, leave all this trouble behind.
JAMIE: We couldn't do that. You know the Doctor would never leave these people. Not while there's
VICTORIA: I know, I know.
JAMIE: Oh, Victoria, you're not going to start again, are you? Look, the Doctor's got enough trouble as it is. Let him just sit and work it out. Anyway, he says there's an obvious answer to this seaweed stuff.
VICTORIA: An answer? What do you mean?
JAMIE: A way of fighting it.
VICTORIA: If it's that obvious he'd have thought of it by now.
JAMIE: Aye.
(Jones, Harris and Perkins enter.)
JONES: Well Doctor, have you thought of a way in which we can attack this weed? Doctor!
DOCTOR: Oh, Miss Jones. No, I'm afraid I haven't.
JONES: Well, have you any idea what it might do next?
DOCTOR: Well, I think it has little alternative but to attack us here.
HARRIS: Here?
PERKINS: But why?
DOCTOR: Because this is the gas distribution centre. It'll want to gain control of it. We must find a way of attacking it's nerve centre before it does.
PERKINS: But where is the nerve centre?
DOCTOR: That's the trouble. We don't know.
HARRIS: And we're not sure yet quite how to destroy it, are we?
DOCTOR: No, but there is something at the back of my mind.
PERKINS: Well what about the oxygen?
DOCTOR: Yes, that is a possibility.
JONES: Then we must put the oxygen supply room under guard.
HARRIS: Right!

[Robson's cabin]

(Robson is asleep when the heartbeat starts up. His eyes open and he looks at the ventilation grille in the wall. Robson gets up and goes to the door.)
ROBSON: Yes. Yes. Yes.

[Outside Robson's cabin]

(Robson attacks the guard from behind with his weed-covered hands. He breathes toxic gas onto his face, knocking him out.)

[Control hall]

(Blake reports the sabotage of the oxygen supply room.)
HARRIS: The whole of the oxygen store?
BLAKE: Yes, sir. There are no reserves left at all.
HARRIS: They seem to be one step ahead of us all the time.
DOCTOR: Yes, I was right. Someone amongst us here is under the control of the weed.
HARRIS: You mean apart from Robson and Van Lutyens?
DOCTOR: Yes, I'm afraid so.
HARRIS: How will we find out who they are?
DOCTOR: I don't know, that's the difficulty.
HARRIS: Well, we must do a personnel check. Now there's a fingerprint file in security.
DOCTOR: Yes.
HARRIS: Doctor, I shall need your help.
DOCTOR: Yes.
(Jamie spots Oak and Quill about to leave.)
JAMIE: Hey, you two. Just a moment. Stop!

[Corridor]

JAMIE: Come back. You wont get away from me!
(Jamie tackles Quill.)
VICTORIA: Careful!
(The Doctor and Harris are at the end of the corridor as Oak gets away. Quill gets out of Jamie's grasp and breathes on him. Jamie staggers, then punches Quill before he can get out of reach. Victoria screams. Quill drops to the floor.)
JAMIE: That soon put paid to him, didn't it. Didn't know what hit him, did he.
DOCTOR: Yes, Jamie, I'm sure you're right.
JAMIE: There's a wee bit of power left in the old McCrimmon punch yet.
DOCTOR: I'm sorry to disillusion you, Jamie, but I don't think it was the punch that did it.
CHIEF: Mister Harris!
HARRIS: What is it?
CHIEF: I think you better come, sir. Quickly!

[Control hall]

(There is a mass of weed and foam on the monitor.)
JONES: What's the trouble?
HARRIS: The pipeline room.
JONES: But it's incredible.
PERKINS: Why can't we do something?
JONES: We'll have to trust this strange Doctor. He's the only one who seems to be able to anticipate events.
PERKINS: Don't you think that in itself is suspect?
JONES: He's our only hope. Come on.

[Pipeline room]

(Jamie points to the transparent panel in the pipeline.)
JAMIE: What's happened to it, Doctor?
DOCTOR: It's beginning to expand, like it did in the Tardis.
JAMIE: Is there no way of stopping it?
DOCTOR: No. I should have thought of this.
JONES: What, do you mean this horrible stuff's growing all the time?
DOCTOR: I'm very much afraid so!
PRICE [OC]: Mister Harris, sir. Mister Harris. Mister Robson's broken out of his cabin. He's attacked the guard!
JAMIE: Doctor, look at that!
(The panel in the pipe starts to crack, then foam burst into the room. A weed tentacle grabs an engineer, pulling him into the foam.)
DOCTOR: Right, Jamie, right back. Back, everyone back. Come along.

[Impeller room]

DOCTOR: Miss Jones, I think it's time you went. Come along.
TANNOY: Emergency alert.
JAMIE: Where's Victoria?
DOCTOR: Well, she was here.
JAMIE: Victoria?
DOCTOR: She was here, standing along side you.
JAMIE: I thought she was with you!
DOCTOR: No!
JAMIE: Where's she gone?
DOCTOR: She must have gone through there.
(But the safety doors between the impeller room and control hall close, locking them in.)
JAMIE: Hey!
DOCTOR: The doors!
JAMIE: They won't open.
DOCTOR: Open these doors! Open these doors! Try here, Jamie!
JAMIE: They're closed, too.
(The Doctor goes to the door to the corridor and holds it open with his body.)
DOCTOR: They're not, come along!
(Jamie is still looking for Victoria.)
DOCTOR: Jamie, the doors, they're heavy. I can't hold them! Jamie, hurry! Jamie! Jamie, come on! This way, in here. Hurry up, I can't hold them!
(Jamie goes over as the gas fills the room and they both get into the corridor just in time.)

[Corridor]

JAMIE: Now what do we do?
DOCTOR: We must look for Victoria. You go that way, I'll go this.
JAMIE: Right.
(At the seaward entrance to the refinery building, Robson is carrying the unconscious Victoria. He puts her in the passenger seat of a Mini Moke then drives away. Klaxons wail across the area.)

[Control hall]

HARRIS: Seal off the pipeline room completely. Close the pipelines in and out. Well, come on, man, don't just stand there! Guards! You must find Mister Robson. Search everywhere.
(The Moke hurtles along the cliff top road to the airstrip. Robson drags Victoria out and carries her to a waiting helicopter, then starts it up and takes off.)

[Control hall]

PRICE: Mister Harris!
HARRIS: What is it?
PRICE: Mister Robson has just taken off.
(The helicopter heads out to sea.)
JAMIE: Hey, have you seen Victoria?
HARRIS: No, I haven't.
JAMIE: Doctor, have you found her yet?
DOCTOR: No, I was hoping you had.
JAMIE: But she was standing right beside us.
DOCTOR: No, no, no.
HARRIS: Doctor, it's Robson. He's trying to get away in one of the company helicopters.
JAMIE: What?
HARRIS: I'm afraid he's got your young girl with him.
DOCTOR: Oh no. Oh no. Can I speak to him from here?
HARRIS: Yes. Price, switch to RT.
PRICE: Yes, sir.
DOCTOR: This one?
PRICE: Yes.
DOCTOR: Robson. Robson. Robson, listen to me. Can you hear me?

[Robson's helicopter]

DOCTOR [OC]: Robson. Come back, man. Come back. Robson, don't you realise what they're trying to do to you? They're trying to control you.
ROBSON: Now listen to me.
DOCTOR [OC]: Robson. Robson.
ROBSON: Listen! Listen!

[Control hall]

ROBSON [OC]: I have the girl. She is my prisoner. She is my hostage. Do you understand? If you want her to live, come over to us. Come over to us.
DOCTOR: Robson. Robson!
PRICE: He's switched off, sir.
JONES: What did he mean, come over to us?
DOCTOR: Well, he meant exactly what he said!
HARRIS: You mean they want you?
DOCTOR: Yes, they must think I'm a serious menace.
HARRIS: But you won't go, surely?
DOCTOR: But of course.
JONES: But we need you here. You're our only hope.
JAMIE: Doctor, we can't let him take Victoria! Now we've got to do something to stop him!
JONES: You can't go with that man. You can see he's not responsible.
DOCTOR: Jamie's right. We've got to go after him.
HARRIS: Yes, you can use a company helicopter.
JONES: Harris! If we let this man go now what hope have we got?
DOCTOR: Miss Jones, I have a feeling that Mister Robson is going to lead us to the nerve centre of the colony.
HARRIS: Price, tell the helicopter crew to stand by. Doctor, come with me. I'll get you some transport. Quickly.

[Harris' office]

HARRIS: Good. Thank you, Price. Tell them not to lose touch. Oh and Price? The Doctor and the boy, are they airborne yet?
PRICE [OC]: No, sir. They're just approaching the airfield.
(Another helicopter is ready to take off as the Doctor and Jamie run over to it. Once aboard, the pilot takes off and they go after Robson. Robson is on final approach to rig.)

[Harris' office]

PRICE [OC]: Mister Harris, sir. Mister Harris, the Doctor's airborne.
HARRIS: Good.

[Control hall]

HARRIS: Doctor, can you see Robson?
DOCTOR [OC]: No, we can't see anything here.
HARRIS: All right, listen carefully. We managed to track him on the radar scope. He's just landed on the control rig complex.
DOCTOR [OC]: The control rig complex.
HARRIS: What? Say again.
DOCTOR [OC]: We are proceeding there now.
JONES: What chance have they got?
HARRIS: Your guess is as good as mine.
JONES: What do we do now?
HARRIS: We sit and wait.
JONES: But we can't
HARRIS: If the Doctor hasn't done something within an hour, I'm evacuating the compound.
JONES: No, it's
HARRIS: And that's final, Miss Jones.

[Doctor's helicopter]

DOCTOR: Jamie, there's the control rig complex.
JAMIE: Hey, Doctor. One of those towers is all covered in white.
DOCTOR: Yes, it's foam. That's the nerve centre.
(They circle, looking for a landing site.)
JAMIE: Robson's helicopter.
DOCTOR: Yes.
JAMIE: We can't land there.
DOCTOR: Oh yes we can, Jamie.
(Their pilot descends to hover over the pad, sending foam flying. They deploy a rope ladder and the Doctor comes down.)

[Control Rig]

DOCTOR: Come on in. The water's lovely.
(Jamie climbs down, the weights in the hem of his kilt preserving his modesty from the turbulence of the rotors.)
DOCTOR: Come on, Jamie.
(Jamie reaches the pad, the Doctor gives the pilot the thumbs-up and he flies away.)
DOCTOR: Goodbye. Now, down the hatch.

[Rig corridor]

(The Doctor and Jamie go down a ladder into a long metal corridor.)
DOCTOR: So far so good, Jamie.
JAMIE: But the driver, will he wait for us?
DOCTOR: Oh yes, he said he'd hang around.
JAMIE: Where do we go from here?
DOCTOR: I think we'll go along down here.
JAMIE: It's like walking into the lion's den.
DOCTOR: Jamie, we're already in the lion's den. What we've got to concentrate on is keeping our heads out of his mouth. Now come on.
(They walk along to another metal staircase going deeper down into the rig.)
JAMIE: It's very quiet. Do you think Victoria really is down here?
DOCTOR: There's nowhere else she can be.
JAMIE: I suppose you're right. Vic
DOCTOR: No, Jamie. Jamie! Now there's no element of surprise!
VICTORIA [OC]: Jamie! Doctor!
JAMIE: See, I was right.
DOCTOR: No, Jamie!
JAMIE: What's the matter?
DOCTOR: If you were hunting what would you do?
JAMIE: Well I would set. Oh I see. You think it might be a trap.
DOCTOR: Might be. Let's be cautious just in case, hey?
(The sound of the heartbeat gets louder as they check each room they come to. The third door is at the end of this corridor.)
DOCTOR: Here we go.

[Rig cabin]

(The Doctor throws open the door and reaches for the light switch. The foam in the room is waist deep with someone standing in the middle of it, weed on his body.)
JAMIE: It's Robson!
ROBSON: Come in, Doctor. We've been waiting for you.

Episode Six

[Rig cabin]

DOCTOR: What do you want with me?
ROBSON: You are going to help our new masters. They need you.
DOCTOR: They need me?
VICTORIA [OC]: Jamie! Doctor!
ROBSON: You are going to help
JAMIE: Victoria.
(Jamie leaves.)
ROBSON: With the conquest of the human planet.
VICTORIA [OC]: Jamie!
JAMIE [OC]: Where are you?
VICTORIA [OC]: In here.
DOCTOR: Don't you realise what they've done to you? They're trying to control your mind, man!
VICTORIA [OC]: Oh, hurry.
JAMIE [OC]: It's locked.
VICTORIA [OC]: Hurry.
ROBSON: The mind does not exist. It is tired. It is dead. It is obsolete. Only our new masters can offer us life.
DOCTOR: Matter will never conquer mind. It's against the law of nature!
ROBSON: The body does not exist. Soon we shall all be one.
(Robson steps forward and breathes toxic gas onto the Doctor.)
DOCTOR: Jamie, hurry!

[Rig corridor]

DOCTOR: Hurry, Jamie.
ROBSON: You cannot escape. You must join us. You must join us. You will join us. (Jamie frees Victoria from a room at the end of the corridor. She screams.)
DOCTOR: Scream again, Victoria!
(She does. Robson stops and clutches his head in pain.)
ROBSON: No! No! No! Stop! Stop! Stop! Stop!
(Robson goes back into the cabin and sinks down into the foam.)
DOCTOR: Come along. It's time we got out of here.
VICTORIA: What about the door?
JAMIE: Yes, should we lock him in?
DOCTOR: No, no. I think it's all right now. The helicopter's waiting. Come along. Mind the stairs, they're slippery.

[Control rig]

(The Doctor, Jamie and Victoria come out of the hatch and go to the heli-pad.)
DOCTOR: Well, where's the helicopter then?
VICTORIA: I can't see anything except this awful foam.
JAMIE: Don't worry, Victoria, it won't hurt you.
DOCTOR: There it is!
ALL: Hey! Hey! Hey!
VICTORIA: Oh, can't he see us?
DOCTOR: Probably not.
JAMIE: He's probably just too scared.
DOCTOR: Oh Jamie, help me get this hatchway covered. We can't hang around here. The helicopter will never see us.
JAMIE: But we'll never get of the rig without it.
DOCTOR: There's Robson's helicopter in there.
JAMIE: But it hasn't got a driver.
DOCTOR: I've been dying to get my hands on one of those things. Come on. Come on.

[Helicopter]

(The Doctor starts up the engine and it begins to take off as the foam tries to smother the machine.)
VICTORIA: Oh the foam, Doctor! I can't see!
DOCTOR: Don't worry, Victoria. We'll soon be out of it.
JAMIE: I hope you know what you're doing.
DOCTOR: Well, we're airborne, aren't we, Jamie? Anyway, Astrid Ferrier. We watched her fly one of these things.
VICTORIA: That's the only time.
DOCTOR: Now, don't worry, Victoria. It's a very primitive machine, you know. It should be easy to control.
VICTORIA: Doctor, look out!
(But flying in three dimensions is not that easy, and the helicopter weaves around, making near-misses of the rig. Oh's and gasps of fear from Victoria and Jamie.)
DOCTOR: Well, that's strange.
JAMIE: What?
DOCTOR: Well, I was always under the impression that you couldn't loop the loop in a helicopter.
JAMIE: What?
VICTORIA: Look out!
(They suddenly loose height, heading back to the rig. The Doctor narrowly avoids a crash.)
PILOT [OC]: Stick back. Stick back. Nose down a bit. Go on. Right pedal down. Right rudder.
(It's the pilot of the other helicopter to the rescue.)
DOCTOR: Right rudder.
PILOT [OC]: Not too much, not too much. Try and keep the nose on the horizon. That's better. Okay. Okay. Now too much. Stick back! Stick back! Stick back, you want to come up now. Come on, you're getting too near the water. Much too near the water. Stick back. Stick back. That's better. Pull her up! Stick back! Stick back quickly! To the right. You're about to hit the water. That's right. Now try and keep everything centralised. Okay, now pull her up. Stick back! Stick back! Quickly, stick back, stick back! Now try and keep the control central.
(The Doctor finally gets his helicopter under a semblance of control.)
DOCTOR: Yes, thank you so much. Oh, just one thing. I've got it up all right and it should be comparatively simple to propel it forward. However, how do I land it?

[Control hall]

HARRIS: It's no good. We won't hear from the Doctor or any of them. We must evacuate the compound.
JONES: No! We said an hour. He's got ten more minutes.
HARRIS: But even if he does come back, what good could he do? The only possible weapon we might have used against the weed has been destroyed.
JONES: That was your entire stock of oxygen, was it?
HARRIS: Yes.
JONES: Right. Perkins, get onto London to the Defence Minister. I want a full red alert on this now. Tell him what's happened and ask him to arrange for as many tankers of oxygen as he can muster to be sent here immediately.
PERKINS: Yes, Miss Jones.
HARRIS: They won't be in time. We must evacuate the compound. The pipeline room is a mass of weed and foam. You've seen how rapidly it reproduces. It could swamp the entire compound at any moment.
JONES: It could, but it hasn't yet, and until it does, we stay here.
HARRIS: And when it does attack, how do you expect to fight it? With what weapons?
DOCTOR: Perhaps I can answer those questions, Mister Harris.
JONES: Doctor! Oh, thank heavens you're alive.
HARRIS: What about Robson? Did you find him?
JAMIE: Aye, we found him all right.
HARRIS: And my wife?
DOCTOR: Well, we didn't see her, no.
HARRIS: No. There's not much hope, is there. What can we do? How can we fight this hideous thing?
DOCTOR: You say there's not much hope. I believe there is.
HARRIS: But even if we succeed in fighting of the weed, what about those people already affected by it?
DOCTOR: Well on our way back here we stopped of at the Medicare Centre. The man that Jamie fought with in the corridor has almost completely recovered.
HARRIS: What?
DOCTOR: Yes, the weed growth on his arm has disappeared and died. He's bemused, he's dazed, but he's alive!
HARRIS: But how? Why? What killed the weed?
DOCTOR: Noise! Sound vibrations.
JONES: How did you find out?
DOCTOR: Victoria discovered it.
VICTORIA: I did?
DOCTOR: Well, yes. You screamed.
VICTORIA: I screamed.
DOCTOR: It's her scream, her particular pattern of sound that does the trick.
HARRIS: So that's why the crews on the rigs spoke softly. The noise affected them.
DOCTOR: Yes, very possibly. Now, before you evacuate this compound, just give me one half hour.
HARRIS: The risk is too great. The entire compound is alive with seaweed.
JONES: Half an hour won't make that much difference. Doctor, what do you think we can do?
DOCTOR: We make a noise, Miss Jones. We make an awful lot of noise!
HARRIS: It's too late. We'll never stop it now.
DOCTOR: But we've got to. It may be too late.
HARRIS: It's impossible, I tell you. It's seeping in from every corner of the compound.
DOCTOR: Yes, but if we can destroy the weed's nerve centre.
JONES: But you said yourself you don't know where the nerve centre is.
DOCTOR: But we do. It's here.
HARRIS: That's the Control Rig.
DOCTOR: Precisely. We must generate enough sound to penetrate the Control Rig.
JONES: But how will you get it there?
DOCTOR: That way. Through the pipelines. Mister Harris, this is the only way to help your wife and all those other people.
HARRIS: Yes, I realise that, but there isn't time.
DOCTOR: Please. Just one half hour.
HARRIS: Price.
PRICE: Sir.
HARRIS: What's happening in the pipeline room?
(A monitor is switched on.)
VICTORIA: Oh, no.
PRICE: Half an hour?
HARRIS: Yes, that's about all we've got. But you're right. We must try.
DOCTOR: Oh, thank you. Now then, Mister Price, where do all these big leads go to?
PRICE: The transmitter and loud speakers down below, sir.
DOCTOR: I see.
PRICE: What's this all about, Doctor?
DOCTOR: Well, if we can boost this equipment to transmit enough sound down the pipeline, we can destroy the weed's nerve centre.
JONES: But do you think this idea will work?
DOCTOR: Have you got a tape recorder or some such thing?
PRICE: Yes, sir.
DOCTOR: Victoria, I want you to scream.
VICTORIA: Scream?
DOCTOR: He will record it. Make a loop of it so that we can repeat it endlessly.
PRICE: Right, sir. What have we got here?
JONES: I hope he knows what he's doing.
JAMIE: Of course he does. I think.
CHIEF: Mister Harris, the impeller shaft. You men, quick!
JONES: Oh come on, Doctor.

[Impeller room]

CHIEF: Look, there!
(The weed and foam smashes through the doors and into the airlock.)

[Control hall]

DOCTOR: Take these magnetised speakers and attach them to the pipeline over there. Jamie, give me a hand.
PRICE: Right, ready miss? Now scream into this. Now.
VICTORIA: What, now?
PRICE: Yes, yes. There's not a moment to lose.
VICTORIA: I can't. It's silly.
PRICE: No, no. Please, please, you have to.
VICTORIA: Oh, Doctor!
DOCTOR: What's the matter, Victoria?
PRICE: She can't scream, sir.
DOCTOR: Oh no! Oh Victoria, that's ridiculous.
VICTORIA: Jamie, you can't scream just like that!
DOCTOR: Everything depends upon you screaming.
(Victoria screams.)
DOCTOR: There you are. I knew you could.
(Victoria screams again as she looks over the Doctor's shoulder to see the foam burst out of the impeller room airlock and start to flood the room.)
HARRIS: Run! Don't just stand there!
DOCTOR: Keep away from it! Keep away!
CHIEF: Shut those doors!
HARRIS: Quick, this way.
(The Chief and Harris come back into the control hall and jam the impeller room door closed. The trapped technicians fall victim to the foam and weed.)
HARRIS: All release valves open! Quick!
JONES: What are you doing, man?
HARRIS: I'm going to save the lives of an awful lot of people, Miss Jones. Close feed lines one to six! Come on, man!
JONES: You mean you're giving up? You're evacuating?
HARRIS: Open your eyes, Miss Jones. Can't you see what's happening? We're gradually being strangled. I can't risk the lives of these men here any longer.
DOCTOR: Just a few more minutes, please, Mister Harris. The scream's ready.
HARRIS: Good!
DOCTOR: And Mister Harris.
HARRIS: All right, all right, what do you want us to do?
DOCTOR: Now then, I've attached the speakers to the pipeline. Victoria's scream will be put through this.
HARRIS: What does that do?
DOCTOR: Well, it's a little toy of my own. Together with the amplifiers, yes, it should produce a sonic laser sound wave.
JONES: You mean like a laser light beam?
DOCTOR: Yes, passing through the pipes. It'll destroy the nerve centre of the weed.
HARRIS: Yes, but will it destroy the weed here?
DOCTOR: Well unfortunately no. No, we have to do battle with that ourselves.
HARRIS: How?
DOCTOR: With these, Mister Price.
PRICE: With what?
DOCTOR: If the weed attacks us here, we simply point these at it and hope for the best. Now, for heaven's sake, don't get in the way of the speakers. The sound'll cut you to pieces. HARRIS: Look there!
DOCTOR: Give me the other two. Let's set up another two.
PRICE: What's the current?
DOCTOR: Come along, no time to waste.
HARRIS: Chief! Chief, quick!
DOCTOR: Here we are. That's it.
JAMIE: Doctor, how many is there? I thought that there was only the one monster.

[Outside the Control hall]

(The Chief and Harris are confronted by a mass of weed creature.)
HARRIS: Back, Chief. Back.

[Control hall]

HARRIS: Full Alert! Close all doors!
DOCTOR: There we are.
HARRIS: Close all doors!
JAMIE: Those doors won't hold!
DOCTOR: Take this and point it at the monster, but don't get in the way of it.
HARRIS: Look out!
(The doors bulge under the weight of the weed creature. Then suddenly they give way. The weed creature is in the doorway.)
DOCTOR: Back, everybody. Onto the platform here.
(Everyone gets onto the raised control platform except Price, who is frozen with fear.)
DOCTOR: Switch it on, man, switch it on! Hold that, Jamie. Which is the connector switch? The connector switch!
(He passes his own portable speaker to JAMIE and goes over (The Doctor shakes Price and he hits the switch.)
DOCTOR: Come on. Switch on your speaker and point it at the creature. Switch on! Go on!
(Victoria's electronic scream rings out but the foam comes closer.)
JAMIE: What's going on?
JONES: It's not working!
DOCTOR: Give it a minute.
JONES: It's not working, I tell you.
(The weed creature falters.)
HARRIS: No! Look!
(The foam begins to retreat and the creature goes back to the doorway, writhing.)
DOCTOR: Behind you! Look behind you! The corridor!
(The monitor shows the corridor clearing as the foam and weed ebbs away. Soon it is almost totally clear.)
JAMIE: It worked.
HARRIS: Doctor, it worked.
DOCTOR: Switch off. Price! Switch off now.
(Blissful silence.)
PRICE: Doctor, you've done it.
DOCTOR: Mister Price, I think you can switch it all off now.
PRICE: What about the weed's nerve centre at the Control Rig?
DOCTOR: What about
PRICE: Do you think we've destroyed that?
DOCTOR: Why don't you go and see, Mister Price.
PRICE: Right.
HARRIS: Price.
PRICE: Yes, sir.
HARRIS: Send out the company helicopters right away to the Control Rig. I want a full report right away.
PRICE: Very good, sir.
JONES: Well Doctor, I don't quite know what to say, except thank you.
DOCTOR: Miss Jones, that will be more than sufficient.
HARRIS: I still can't believe it.
DOCTOR: What's the matter, eh?
VICTORIA: I don't know. I'm always frightened.
DOCTOR: Well, of course.
VICTORIA: Oh, Doctor, I can't.
DOCTOR: It's all right.
VICTORIA: I can't.
HARRIS: Doctor, they're safe!
DOCTOR: It's all right, they're safe.
VICTORIA: I can't.
DOCTOR: They're safe. Listen, they're safe. Come along and see.
HARRIS: They're all safe! We've won! Isn't it marvellous? Maggie! Maggie! Mister Robson, can you hear me?
ROBSON [OC]: Yes, Mister Harris, we can.
MAGGIE [OC]: Yes, darling, we can hear you.
HARRIS: Good, good. Are you all well? Has the weed gone?
ROBSON [OC]: The weed? Oh yes, yes, it's gone.
HARRIS: What about Van Lutyens? I don't suppose you
ROBSON [OC]: No, he's fine. He's well.
MAGGIE [OC]: Darling, we're all all right, I promise you.
HARRIS: Quiet, everybody, quiet! Mister Robson, we're sending out one of the company helicopters to you right away. You'll be back with us in less than an hour.

[Harrises' quarters]

(On the patio that evening.)
ROBSON: Oh, I should have listened to you in the first place, Mister Harris.
HARRIS: Oh, I doubt it would have helped. As it turned out, we were lucky we didn't tamper with the weed.
DOCTOR: Oh, yes.
MAGGIE: We'll the next time you ask me to get something from your desk, you can do it yourself.
ROBSON: To think I wanted to keep you locked up, Doctor.
DOCTOR: Well, lots of people have tried.
HARRIS: They didn't want to.
ROBSON: That was a very splendid dinner, Mrs Harris. Now if you'll excuse me, I'm very tired.
DOCTOR: Oh, really. Oh, dear. There we are.
ROBSON: See you in the morning, Doctor?
DOCTOR: Well, no. No, as a matter of fact, we must be on our way.
ROBSON: Oh, dear. Where are you going?
DOCTOR: Well, we haven't quiet decided yet.
JAMIE: Aye, even if we had it wouldn't make any difference. We wouldn't get there. Not with him.
ROBSON: If you're ever around here again, do drop in. And in the front gate this time, just to avoid any unfortunate incidents.
DOCTOR: Yes, I will.
HARRIS: Good night, Mister Robson.
ROBSON: Good night. Bye, Mrs Harris.
DOCTOR: Goodbye, Mister Robson. Well, I suppose I think it's time we went. Jamie. Victoria.
JAMIE: Hey, Victoria. Wakey, wakey. What's the matter?
DOCTOR: You don't want to come with us, do you, Victoria.
VICTORIA: I don't know. I don't really want to leave you.
DOCTOR: Well, I suspected as much.
VICTORIA: Would you mind?
JAMIE: Victoria, you can't
DOCTOR: Just a minute, Jamie. You mean you want to stay here and settle down. Well, if you want to, you must.
VICTORIA: I'm sorry.
DOCTOR: No, that's all right. Mrs Harris, I wonder if you'd mind if Victoria stayed with you for a little while. You see, she's got no parents or home and it is a bit difficult
MAGGIE: Well, of course. We'd be delighted to have you for as long as you want to stay.
VICTORIA: Oh, would you?
MAGGIE: Yes.
DOCTOR: There, thank you very much. Jamie and I will stay for another day, just in case you want to think again.
JAMIE: Look, we'll talk it over later.
DOCTOR: Now, Jamie. She must make up her own mind. It's her own life. It's her decision.
JAMIE: Aye.

[Control hall]

PRICE: Thank you, Rig D. Normal function on all channels. Control checks positive. Closing down now. All communications remain on standby.
ROBSON: All right, Price?
PRICE: Oh yes, thank you, sir. Back to normal.
ROBSON: Relief?
PRICE: Crews on their way, sir.
ROBSON: Bet you could do with a bit of shut-eye.
PRICE: Oh, I don't know. I think I'm a bit past it.
ROBSON: Go out like a light, eh?
PRICE: Probably.
ROBSON: Chief still here?
PRICE: Yes, in the impeller room, sir.
ROBSON: Goodnight, Price.
PRICE: Goodnight, sir.

[Impeller room]

ROBSON: Hello, Chief.
CHIEF: Mister Robson.
ROBSON: Sound as a bell, eh?
CHIEF: Almost, sir.
ROBSON: Almost?
CHIEF: Still half a point off capacity.
ROBSON: Is it?
CHIEF: The main control valve was slightly damaged. They're working on it now. Be up to our normal output in the morning. There's still one or two minor repairs to be done.
ROBSON: Not tonight, Chief.
CHIEF: Well, why not?
ROBSON: Get some sleep. Don't argue. Leave it to the relief.
CHIEF: All right.
ROBSON: Where do you lot think you're going? There's another three minutes before your relief arrives.
CHIEF: Nice to know you're back to normal, sir.
ROBSON: If I didn't know you better, Chief, I would swear you were giving me lip.
CHIEF: Oh, I wouldn't dream of doing that, sir.
ROBSON: Wouldn't you? Goodnight, Chief.
CHIEF: Goodnight, sir.

[Harrises' quarters]

JAMIE: Are you not tired?
VICTORIA: No. No, I'm fine. I'm not tired at all.
JAMIE: Do you know what the Doctor's just gone and done?
VICTORIA: No.
JAMIE: He's only gone down the beach for a swim. He gets worse. You're still not sure, are you?
VICTORIA: Yes. But it doesn't make it any easier leaving you and the Doctor.
JAMIE: Aye, we've been together a long time now. Has the Doctor said anything to you?
VICTORIA: No. No, you know what he's like, he wouldn't. He believes in people making up their own minds.
JAMIE: Oh, Victoria. Do you think you'll be happy here?
VICTORIA: Oh, I think so. The Harrises are very nice people.
JAMIE: Yes, I know that, but they're not from your time, are they?
VICTORIA: I wouldn't be at ease back in Victorian times. I had no parents or family left there anyway.
JAMIE: Aye, that's true. Oh, well.
VICTORIA: Jamie.
JAMIE: Yes?
VICTORIA: You wouldn't go without saying goodbye, would you?
JAMIE: Of course not. That won't be till the morning anyway. Goodnight, Victoria.
VICTORIA: Goodnight, Jamie.
(They hug and kiss.)

[Beach]

(The next morning, Victoria and the Harrises say farewell to the Doctor and Jamie. The Tardis is floating offshore again so the Doctor and Jamie have to use the rubber dinghy to get to it. Jamie waves. Victoria waves back, crying, and Maggie hugs her.)

[Tardis]

(They can see Victoria on the scanner.)
JAMIE: We can't just leave her.
DOCTOR: We are not leaving her, Jamie. It was her decision to stay. She'll be quite all right with the Harrises. Now don't worry so much, Jamie.
JAMIE: I'm not, I'm just. Och, come on, let's go.
DOCTOR: Well, where would you like to go?
JAMIE: I couldn't care less.
DOCTOR: I was fond of her too, you know, Jamie.