(The Doctor is under the car, struggling with the ATMOS.)
DONNA: He's going to choke. Doctor!
DOCTOR: It won't open.
(Sylvia comes back out of the house with an axe, closes the bonnet and breaks the windscreen.)
SYLVIA: Well, don't just stand there. Get him out.

[ATMOS Factory]

SOLDIER [OC]: All soldiers to withdraw. Make the factory secure and take positions on the ground floor.
MACE: Wicowsky, take the soldiers into the factory. Make the area secure. Seal off doors and windows.
(The troops push the vehicles out of the loading bay.)
SOLDIER: We've tried everything, it just won't stop.

[Mobile HQ]

(Mace goes to a female officer on the bank of computer screens.)
MACE: What have we got?
PRICE: ATMOS is running wild, sir. It can't be stopped, it's everywhere. The whole planet.
(Red blobs are covering the inhabited areas on the big map. Martha 2 takes over from another computer user and enters 'her' security clearance code to get into the NATO Defence System.)

[Outside the Nobles' home]

(Wilf is being taken to safety.)
WILF: Thanks.
DONNA: I can't believe you've got an axe.
SYLVIA: Burglars.
DOCTOR: Get inside the house. Just try and close off the doors and windows.
(Jenkins is driving a black cab.)
JENKINS: Doctor. This is all I could find that hasn't got ATMOS.
DOCTOR: Donna, you coming?
DONNA: Yeah.
SYLVIA: Donna. Don't go. Look what happens every time that Doctor appears. Stay with us, please.
WILF: You go, my darling.
SYLVIA: Dad!
WILF: Don't listen to her. You go with the Doctor. That's my girl.
(Donna gets into the cab.)
WILF: Bye.
(Martha 2 finishes downloading NATO's Security Protocols onto a memory stick, and leaves Mobile HQ. Once outside, she downloads it into her mobile phone.)

[Spaceship]

SKORR: Success. The operative has the necessary information.
STAAL: Good work for a female. Now she must be protected.
SKORR: I will prepare an attack squad.
RATTIGAN: This is it, isn't it. Oh man, this is war!
STAAL: How does it feel, boy?
RATTIGAN: Magnificent.

[Industrial estate]

NEWS 24: The Government has declared a state of emergency. People are being told to stay away from all cars with ATMOS devices attached.
AMNN: The gas appears to be toxic. We are warning anyone and everyone, stay away from the cars. Repeat, stay away from your cars.
DOCTOR: Ross, look after yourself. Get inside the building.
JENKINS: Will do. Greyhound Forty to Trap One. I have just returned the Doctor to base safe and sound. Over. (Martha 2 hears the message on her walkie-talkie.)

[Mobile HQ]

MACE: Trap One. Received. Over.
MARTHA 2: Sir. Message from the Doctor. He says Code Red Sontaran.
MACE: All troops. Code Red Sontaran. Code Red Sontaran.

[Industrial estate]

DONNA: The air is disgusting.
DOCTOR: It's not so bad for me. Go on, get inside the Tardis. Oh, I've never given you a key. Keep that. Go on, that's yours. Quite a big moment really.
DONNA: Yeah, maybe we can get sentimental after the world's finished choking to death.
DOCTOR: Good idea.
DONNA: Where are you going?
DOCTOR: To stop a war.
(The Doctor runs to the ATMOS factory while Donna lets herself into the Tardis.)

[Mobile HQ]

DOCTOR: Right then, here I am. Good. Whatever you do, Colonel Mace, do not engage the Sontarans in battle. There is nothing they like better than a war. Just leave this to me.
MACE: And what are you going to do?
DOCTOR: I've got the Tardis. I'm going to get on board their ship.
(Martha taps her phone, and Grey and Harris snap to attention.)
DOCTOR: (to Martha) Come on.

[Industrial estate]

(Grey and Harris fix devices to the outside of the Tardis.)
HARRIS: Ready for transport.
(The Tardis vanishes.)

[Spaceship]

STAAL: The spoils of war. The Doctor's infamous vessel in Sontaran hands.
RATTIGAN: It's time I made a move, sir. I have soldiers of my own. I'll tell them of the honour and the glory, sir. I'll tell them that Planetfall is coming.
Rattigan teleports back to the Academy.)
SKORR: He is behaving exactly as predicted, sir.
(Donna opens the Tardis door, looks out, then closes it again.)
STAAL: None of the humans can guess our true purpose.

[Industrial estate]

MARTHA 2: But where's the Tardis?
DOCTOR: Taste that, in the air. Yuck. That sort of metal tang. Teleport exchange. It's the Sontarans. They've taken it. I'm stuck on Earth like, like an ordinary person. Like a human. How rubbish is that? Sorry, no offence, but come on.
MARTHA 2: So what do we do?
DOCTOR: Well, I mean, it's shielded. They could never detect it.
MARTHA 2: What?
DOCTOR: I'm just wondering, have you phoned your family and Tom?
MARTHA 2: No. What for?
DOCTOR: The gas. Tell them to stay inside.
MARTHA 2: Course I will, yeah but, what about Donna? I mean, where's she?
DOCTOR: Oh, she's gone home. She's not like you. She's not a soldier. Right. So. Avanti.

[Rattigan Academy]

(The building has a lovely view of West London - Post Office Tower, Eye - disappearing in a layer of smog. The students stand on the lawn, looking.)
RATTIGAN: Leave it. Turn away. Civilisation is falling.
MAN: But it's all over the news, sir. It's everywhere. Paris and New York.
RATTIGAN: It's time I told you. All of you. It's time I revealed what our work has been for.

[Mobile HQ]

DOCTOR: Change of plan.
MACE: Good to have you fighting alongside us, Doctor.
DOCTOR: I'm not fighting. I'm not-fighting, as in not hyphen fighting, got it? Now, does anyone know what this gas is yet?
MARTHA 2: We're working on it.
PRICE: It's harmful, but not lethal until it reaches eighty percent density. We're having the first reports of deaths from the centre of Tokyo City.
DOCTOR: And who are you?
PRICE: Captain Marion Price, sir.
DOCTOR: Oh, put your hand down. Don't salute.
MACE: Jodrell Bank's traced a signal, Doctor, coming from five thousand miles above the Earth. We're guessing that's what triggered the cars.
DOCTOR: The Sontaran ship.
MACE: NATO has gone to Defcon One. We're preparing a strike.
DOCTOR: You can't do that. Nuclear missiles won't even scratch the surface. Let me talk to the Sontarans.
MACE: You're not authorised to speak on behalf of the Earth.
DOCTOR: I've got that authority. I earned that a long time ago.
(The Doctor sticks his sonic screwdriver into the communications system.)
DOCTOR: Calling the Sontaran Command Ship

[Spaceship]

DOCTOR [hologram]: Under Jurisdiction Two of the Intergalactic Rules of Engagement.

[Tardis]

(The scanner briefly shows a picture of Rose Tyler, then -)
DOCTOR [on scanner]: This is the Doctor.
DONNA: Doctor, I'm here. Can you hear me?

[Spaceship]

STAAL: Doctor, breathing your last?

[Mobile HQ]

MACE: My God, they're like trolls.
DOCTOR: Yeah, loving the diplomacy, thanks. So, tell me, General Staal, since when did you lot become cowards?
STAAL [on monitor]: How dare you!
MACE: Oh, that's diplomacy?
STAAL [on monitor]: Doctor, you impugn my honour.
DOCTOR: Yeah, I'm really glad you didn't say belittle, because then I'd have a field day. But poison gas? That's the weapon of a coward and you know it.

[Spaceship]

DOCTOR [hologram]: Staal, you could blast this planet out of the sky

[Mobile HQ]

DOCTOR: And yet you're sitting up above watching it die. Where's the fight in that? Where's the honour? Or

[Spaceship]

DOCTOR [hologram]: Are you lot planning something else, because this isn't normal Sontaran warfare. What are you lot up to?
STAAL: A general would be unwise to reveal

[Mobile HQ]

STAAL [on monitor]: His strategy to the opposing forces.
DOCTOR: Ah, the war's not going so well, then. Losing, are we?
STAAL [on monitor]: Such a suggestion is impossible.
MACE: What war?
DOCTOR: The war between the Sontarans and the Rutans. It's been raging, far out in the stars, for fifty thousand years. Fifty thousand years of bloodshed, and for what?

[Spaceship]

STAAL: For victory. Sontar-ha.

[Mobile HQ]

STAAL [on monitor]: Sontar-ha. Sontar-ha. Sontar-ha. Sontar-ha. Sontar-ha.
DOCTOR: Give me a break.
(The Doctor changes channels with the screwdriver, to a cartoon.)
MACE: Doctor. I would seriously recommend that this dialogue is handled by official Earth representation.
(And back to the Sontarans.)
DOCTOR: Finished?
STAAL [on monitor]: You will not be so quick to ridicule when you'll see our prize. Behold. We are the first Sontarans in history to capture a Tardis.
DOCTOR: Well, as prizes go, that's noble.

[Tardis]

DOCTOR [on scanner]: As they say in Latin, Donna nobis pacem.
DONNA: That's me. I'm here.
DOCTOR [on scanner]: Did you never wonder about its design? It's a phone box. It contains a phone. A telephonic device for communication. Sort of symbolic. Like, if only we could communicate, you and I.
STAAL [OC]: All you have communicated is your distress, Doctor.
DONNA: Oh, my God.
(Donna picks up Martha's phone.)

[Mobile HQ]

DOCTOR: Big mistake though, showing it to me.

[Tardis]

DONNA: But who do I phone?

[Mobile HQ]

DOCTOR Because I've got remote control.

[Spaceship]

STAAL: Cease transmission!

[Tardis]

DONNA: Doctor, what number are you on?
(The scanner goes blank.)
DONNA: You haven't even got a number.

[Spaceship]

STAAL: Remove the box from the War Room, beyond the transmission field.

[Mobile HQ]

DOCTOR: Ah, well.
MACE: That achieved nothing.
DOCTOR: Oh, you'd be surprised.

[Tardis]

(Donna is jolted around as Sontarans move the Tardis.)
DONNA: But what do I do?

[Academy laboratory]

RATTIGAN: All this stuff we've been building. All this invention. Where's it been heading? Gravity densifiers, hydroponics, atmospheric conversion, ecoshells. More then enough to build a brand new world.
MAN: Luke, we haven't got time for this. I've got to find my parents.
RATTIGAN: Oh, but this isn't just theory. I'm talking Planetfall, for all of us. A brand new start for a brand new human race. Look. A new world, far out, beyond Alpha Geminorum, just waiting for us. Its official destination is Castor Thirty Six. I think of it as Earth Point Two. I did wonder about Rattigan's World, but we can take a vote on that.
MAN: What the hell are you on about?
RATTIGAN: This is where we're going. I have partners willing to take us there.
WOMAN: Oh, he's lost it. I haven't got time for this.
RATTIGAN: Excuse me, I haven't finished. Where are you going?
WOMAN: To find my brother.
RATTIGAN: I didn't say you could leave.
WOMAN: I told him to put ATMOS is his car. I've got to go and help him.
(Rattigan takes a gun from his belt.)
RATTIGAN: Stay where you are.
WOMAN: What do you think you're doing?
MAN: Luke, put that down.
RATTIGAN: But, I did this for you, don't you see? We've spent all our lives excluded. The clever ones. They've laughed at us and pulled us down, those ordinary people out there. Those cattle. This is our chance to leave them behind.
MAN: You mean you want them dead?
RATTIGAN: And I chose you to survive. With Planetfall we can start again. We can build and breed, we can prosper, we can do anything.
WOMAN: We're going to breed?
RATTIGAN: I've designed a mating program. I've planned the whole thing.
WOMAN: Well then, shoot me.
RATTIGAN: Stay where you are. Stay where you are, I said. Stay where you are.
(She leaves, and other students follow her.)
RATTIGAN: Stay where you are. That's an order!
MAN: Castor Thirty Six? You're just sick.
(Rattigan is left alone.)
RATTIGAN: I guess that just proves it. I'm cleverer then you. I'm cleverer then everyone, do you hear me? I'm clever!

[Nobles' home]

NEWS 24: The United Nations has issued a directive worldwide, telling urban populations to stay indoors. Those in rural areas are being ordered to stay away from all major cities. There are reports from every country in Europe of thousands of people walking across country to escape. And on the Eastern seaboard of America it's said to be reminiscent of Dunkirk, with boats taking refugees out into the Atlantic.
AMNN: With the freeways blocked by ATMOS cars, populations of major cities are now walking across open country to escape the fumes. It is being likened to a Biblical plague. Some are calling this the End of Days.
(Donna calls one number that she knows.)
DONNA [OC]: Mum, you all right?
SYLVIA: Donna. Where are you, sweetheart?
WILF: Is that her?
SYLVIA: Oh, just finish the job. Your granddad's sealing us in. He's sealing the windows. Our own house, and we're sealed in. All those things they said about pollution

[Tardis]

SYLVIA [OC]: And ozone and carbon, they're really happening aren't they?
DONNA: There's people working on it, Mum. They're going to fix it, I promise.
SYLVIA [OC]: Oh, like you'd know. You're so clever.
DONNA: Oh, don't start.

[Nobles' home]

DONNA [OC]: Please don't.
SYLVIA: I'm sorry. I wish you were here.
WILF: Now, come on, Sylvia. Look, that doesn't help.

[Tardis]

WILF [OC]: Donna, where are you?
DONNA: It's sort of hard to say. You all right?
WILF [OC]: Yeah.

[Nobles' home]

WILF: Fighting fit, yeah. Is he with you, the Doctor?
SYLVIA: Oh, the Doctor.

[Tardis]

DONNA: No. I'm all on my own.

[Nobles' home]

WILF: Look, you promised he was going to look after

[Tardis]

WILF [OC]: You.
DONNA: He will, Gramps. There's something he needs me to do.

[Nobles' home]

DONNA [OC]: I just don't know what.
WILF: Well, I mean, the whole place is covered. The whole of London, they're saying. The whole, the whole world. It's the scale of it, Donna.

[Tardis]

WILF [OC]: I mean, how can one man stop all that?
DONNA: Trust me. He can do it.

[Nobles' home]

WILF: Yeah, well, if he doesn't, you tell him he'll have to answer to me.

[Tardis]

DONNA: I will. Just as soon as I see him, I'll tell him.

[Nobles' home]

WILF: Huh.
(He puts the phone down. Sylvia looks out at the smog-filled street.)

[Mobile HQ]

(The Doctor reads Martha 2's clipboard.)
MARTHA 2: There's carbon monoxide, hydrocarbons, nitrogen oxides, but ten percent unidentified. Some sort of artificial heavy element we can't trace. You ever seen anything like it?
DOCTOR: It must be something the Sontarans invented. This isn't just poison. They need this gas for something else. What could that be?
PRICE: Launch grid online and active.
MACE: Positions, ladies and gentlemen, Defcon One initiatives in progress.
DOCTOR: What? I told you not to launch.
MACE: The gas is at sixty percent density. Eighty percent and people start dying, Doctor. We've got no choice.
PRICE: Launching in sixty, fifty nine, fifty eight, fifty seven, fifty six. Worldwide nuclear grid now coordinating. Fifty four, fifty three.

[Spaceship]

STAAL: Ha! The planet is going nuclear. I admire them. The bravery of idiots is bravery, nonetheless.
SONTARAN: The operative is in place, sir.
STAAL: Commander Skorr. Is the attack squad ready?
SKORR: Ready and eager for battle, sir. We've been watching for long enough. It'll be good to taste blood.

[Mobile HQ]

DOCTOR: You're making a mistake, Colonel. For once, I hope the Sontarans are ahead of you.
PRICE: North America, online. United Kingdom, online. France, online. India, online. Pakistan, online. China, online. North Korea, online. All systems locked and coordinated. Launching in ten, nine, eight, seven, six, five
MACE: God save us.
PRICE: Four, three, two, one.
(Martha 2 activates her phone hack. Launch yes/no? She presses No.)
PRICE: Zero.
(Nothing happens. The world map goes blank.)
MACE: What is it? What happened? Did we launch? Well, did we?
PRICE: Negative, sir. The launch codes have been wiped, sir. It must be the Sontarans.
MACE: Can we override it?
PRICE: Trying it now, sir.
DOCTOR: Missiles wouldn't even dent that ship, so why are the Sontarans so keen to stop you? Any ideas?
MARTHA 2: How should I know?

[Spaceship]

STAAL: Now, protect the operative.
(Sontaran troops march up from the ATMOS factory basement.)

[ATMOS factory]

JENKINS: It's stinking out there. Shush. Keep it down lads.
(Sontarans come around the corner.)
JENKINS: Enemy within. At arms. Greyhound Forty declaring Absolute emergency.

[Mobile HQ]

JENKINS [OC]: Sontarans within factory grounds. East corridor, grid six.
MACE: Absolute emergency. Declaring Code Red. All troops, Code Red.
DOCTOR: Get them out of there.
MACE: All troops, open fire.

[ATMOS factory]

JENKINS: Guns aren't working. Inform all troops, standard weapons do not work.
(The troops die quickly.)
JENKINS: Tell the Doctor it's that cordolaine signal.

[Mobile HQ]

JENKINS [OC]: He's the only one who can stop them.
(Skorr kills Jenkins.)
MACE: Greyhound Forty, report. Over. Greyhound Forty, report. Greyhound Forty, report.
DOCTOR: He wasn't Greyhound Forty. His name was Ross. Now listen to me, and get them out of there!
MACE: Trap One to all stations. Retreat. Order imperative. Immediate retreat.

[ATMOS factory]

SOLDIER: Retreat. Retreat.
(It is a massacre.)
GRAY + HARRIS: Reporting for duty, sir.
(A helmeted Sontaran shoots them.)
SKORR: This is too easy. They're running like slimebait from a speelfox. This isn't war, this is sport.
(The loading bay doors come down.)

[Mobile HQ]

MACE: They've taken the factory.
DOCTOR: Why? They don't need it. Why attack now? What are they up to? Times like this, I could do with the Brigadier. No offence.
MACE: None taken. Sir Alistair's a fine man, if not the best. Unfortunately, he's stranded in Peru.
PRICE: Launch grid back online.
(Martha taps No again and the grid goes blank.)
PRICE: They're inside the system, sir. It's coming from within UNIT itself.
MACE: Trace it. Find out where it's coming from, and quickly. Gas levels?
PRICE: Sixty six percent in major population areas, and rising.

[Spaceship]

SKORR [OC]: Commander Skorr reports victory with many glorious deaths.
(Rattigan teleports in.)
RATTIGAN: Sorry to report, sir, I've failed. They wouldn't come. The students, they didn't have the imagination to believe.
STAAL: A pity. We've lost our target practice.
RATTIGAN: What do you mean?
STAAL: Upon arrival on board this ship, your students would have been shot down. Perhaps they were more clever then you thought.
RATTIGAN: You promised.
STAAL: There was no Planetfall. Castor Thirty Six, indeed. We only needed you for installation of the ATMOS system.
RATTIGAN: No, but I'm on your side. I did everything you wanted. And it's not ATMOS system. That's a tautology. It's just ATMOS.
STAAL: Execute him.
(Rattigan teleports away.)
STAAL: A coward's retreat. Now close all teleport links to Earth. Isolate them as they perish.

[Mobile HQ]

(The Doctor and Mace are in his tiny office.)
MACE: Why are they defending the factory only after we were inside?
DOCTOR: Because they wanted UNIT here. You gave them something they needed. Something now hidden inside the factory. Something precious.
MACE: We've got to recover it. This cordolaine signal thing, how does it work?
DOCTOR: It's the bullets. It causes expansion of the copper shell.
MACE: Excellent. I'm on it.
DOCTOR: For the billionth time, you can't fight Sontarans.
(He goes to the nearest UNIT officer.)
DOCTOR: (sotto) Phone. Have you got a phone? I need your mobile. Quickly, hurry up.
(The Doctor returns to the tiny office and watches Martha 2.)

[Tardis]

DONNA: What's happened?

[Mobile HQ]

DONNA [OC]: Where are you?
DOCTOR: Still on Earth. But don't worry, I've got my secret weapon.
DONNA [OC]: What's that?
DOCTOR: You.

[Tardis]

DONNA: Oh. Somehow that's not making me happy. Can't you just zap us down to Earth

[Mobile HQ]

DONNA [OC]: With that remote thing?
DOCTOR: Yeah, I haven't got a remote, though I really should. I need you on that ship. That's why I made them move

[Tardis]

DOCTOR [OC]: The Tardis. I'm sorry

[Mobile HQ]

DOCTOR: But you've got to go outside.

[Tardis]

DONNA: But there's Sonteruns out there.

[Mobile HQ]

DOCTOR: Sontarans. But they'll all be on battle stations right now. They don't exactly walk about

[Tardis]

DOCTOR [OC]: Having coffee. I can talk you through it.
DONNA: But what if they find me?

[Mobile HQ]

DOCTOR: I know, and I wouldn't ask, but there's nothing else I can do. The whole planet is choking, Donna.

[Tardis]

DONNA: What do you need me to do?
DOCTOR: The Sontarans are inside the factory which means they've got a teleport link with the ship, but they'll have deadlocked it. I need you to

[Mobile HQ]

DOCTOR: Reopen the link.

[Tardis]

DONNA: But I can't even mend a fuse.

[Mobile HQ]

DOCTOR: Donna, stop talking about yourself like that. You can do this.

[Tardis]

DOCTOR [OC]: I promise.
(Donna peeks outside the Tardis. It is being guarded.)
DONNA: There's a Sonterun. Sontaran.

[Mobile HQ]

DOCTOR: Did he see you?

[Tardis]

DONNA: No, he's got his back to me.
DOCTOR [OC]: Right, Donna, listen. On the back of his neck

[Mobile HQ]

DOCTOR: On his collar there's a sort of plug, like a hole. The Probic vent.

[Tardis]

DOCTOR [OC]: One blow to the Probic vent knocks 'them out.
DONNA: But he's going to kill me.

[Mobile HQ]

DOCTOR: I'm sorry. I swear I'm so sorry, but you've got to try.

[Spaceship]

(Donna gets the mallet that the Doctor uses on the Tardis console, sneaks outside and gives the Sontaran a hefty whack on the vent. He goes down like a sack of potatoes.)
DONNA: Back of the neck. 
DOCTOR [OC]: Now then, you got to find the external junction feed to the teleport.
DONNA: What, what's it look like?
DOCTOR [OC]: A circular panel on the wall.

[Mobile HQ]

DOCTOR: Big symbol on the front, like a, like a

[Spaceship]

DOCTOR [OC]: Letter T with a horizontal line through it. Or, or, two Fs back to back.
DONNA: Oh. Well, there's a door.

[Mobile HQ]

DOCTOR: Should be a switch by the side.

[Spaceship]

DONNA: Yeah there is. But it's Sontaran shaped, you need three fingers.

[Mobile HQ]

DOCTOR: You've got three fingers.

[Spaceship]

DONNA: Oh, yeah.

[Mobile HQ]

DONNA [OC]: I'm through.
DOCTOR: Oh, you are brilliant, you are.

[Spaceship]

DONNA: Shut up. Right.

[Mobile HQ]

DONNA [OC]: T with a line through it.
DOCTOR: Got to go. Keep the line open.
MACE: Counter attack.
DOCTOR: I said, you don't stand a chance.
MACE: Positions. That means everyone.
(Mace tosses a gas mask to the Doctor.)
MARTHA 2: You're not going without me.
DOCTOR: Wouldn't dream of it.
(Up on the spaceship, Donna hides as more Sontaran troops march past.)

[Industrial estate]

MACE: Latest firing stock. What do you think, Doctor?
DOCTOR: Are you my mummy?
MACE: If you could concentrate. Bullets with a rad-steel coating. No copper surface. Should overcome the cordolaine signal.
DOCTOR: But the Sontarans have got lasers. You can't even see in this fog. The night vision doesn't work.
MACE: Thank you, Doctor. Thank you for your lack of faith. But this time, I'm not listening.
(Mace removes his gas mask.)
MACE: Attention, all troops. The Sontarans might think of us as primitive, as does every passing species with an axe to grind. They make a mockery of our weapons, our soldiers, our ideals. But no more. From this point on, it stops. From this point on, the people of Earth fight back, and we show them. We show the warriors of Sontar what the human race can do. Trap One to Hawk Major. Go, go, go.
(There is a sudden massive downdraft, blowing the gas away.)
MACE: It's working. The area's clearing. Engines to maximum.
DOCTOR: It's the Valiant.
MACE: UNIT Carrier Ship Valiant reporting for duty, Doctor. With engines strong enough to clear away the fog.
(The gas masks can now be removed.)
DOCTOR: Whoa, that's brilliant.
MACE: Getting a taste for it, Doctor?
DOCTOR: No, not at all. Not me.
MACE: Valiant, fire at will.
(Six green beams from the Valiant converge to form one that hits the ATMOS factory. Meanwhile, UNIT soldiers use rocket launchers to blast away the loading bay doors. It is the Sontaran's turn to be massacred.)

[ATMOS factory]

MACE: East and north secure. Doctor?
DOCTOR Donna, hold on. I'm coming.
MARTHA 2: Shouldn't we follow the Colonel?
(The Doctor scans the area with his sonic screwdriver.)
DOCTOR: Nah, you and me, Martha Jones. Just like old times.
(Martha 2 stops the nuclear strike again.)
DOCTOR: Alien technology, this-a way.
(Skorr shoots a couple of soldiers.)
SKORR: The honour of battle. The glory!

[Basement]

(The corridor lights come on.)
DOCTOR: No Sontarans down here. They can't resist a battle. Here we go.

[Clone laboratory]

DOCTOR: Oh, Martha, I'm so sorry. Still alive.
(Martha 2 points a gun at the Doctor's head.)
DOCTOR: Am I supposed to be impressed?
MARTHA 2: Wish you carried a gun now?
DOCTOR: Not at all.
MARTHA 2: I've been stopping the nuclear launch all this time.
DOCTOR: Doing exactly what I wanted. I needed to stop the missiles, just as much as the Sontarans. I'm not having Earth start an interstellar war. You're a triple agent.
MARTHA 2: When did you know?
DOCTOR: About you? Oh, right from the start. Reduced iris contraction, slight thinning of the hair follicles on the left temple. And, frankly, you smell. You might as well have worn a T shirt saying clone. Although, maybe not in front of Captain Jack. You remember him, don't you? Because you've got all her memories. That's why the Sontarans had to protect her, to keep you inside UNIT. Martha Jones is keeping you alive.
(The Doctor takes the device off Martha's head, and the clone collapses. He kicks the gun away.)
DOCTOR: It's all right, it's all right, I'm here, I'm here. I've got you, I've got you.
MARTHA: There was this thing, Doctor, this alien, with this head.
(The mobile phone rings.)
DOCTOR: Oh! Blimey, I'm busy. Got it?

[Spaceship]

DONNA: Yes. Now hurry up.
DOCTOR [OC]: Take off the covering. All the blue switches inside

[Clone laboratory]

DOCTOR: Flick them up like a fuse box, and that should get the teleport working.
MARTHA: Oh, my God. That's me.

[ATMOS factory]

MACE: You will face me, sir.
(Skorr turns and Colonel Mace shoots him three times in the head.)
SKORR: Wonderful.
(Skorr dies.)

[Clone laboratory]

(The Doctor has put his coat around Martha and is working on the teleport.)
MARTHA 2: Don't touch me.
MARTHA: It's not my fault. The Sontarans created you, but you had all my memories.
MARTHA 2: You've got a brother, sister, mother and father.
MARTHA: If you don't help me, they're going to die.
MARTHA 2: You love them.
MARTHA: Yes. Remember that?
DOCTOR: The gas. Tell us about the gas.
MARTHA 2: He's the enemy.
MARTHA: Then tell me. It's not just poison, what's it for? Martha, please.
MARTHA 2: Caesofine concentrate. It's one part of Bosteen, two parts Probic five.
DOCTOR: Clonefeed. It's clonefeed!
MARTHA: What's clonefeed?
DOCTOR: Like amniotic fluid for Sontarans. That's why they're not invading. They're converting the atmosphere, changing the planet into a clone world. Earth becomes a great big hatchery. Because the Sontarans are clones, that's how they reproduce. Give them a planet this big, they'll create billions of new soldiers. The gas isn't poison, it's food.
MARTHA 2: My heart. It's getting slower.
MARTHA: There's nothing I can do.
MARTHA 2: In your mind, you've got so many plans. There's so much that you want to do.
MARTHA: And I will. Never do tomorrow what you can do today, my mum says, because
MARTHA 2: Because you never know how long you've got. Martha Jones. All that life.
(The clone dies. Martha takes back her engagement ring.)

[Spaceship]

DONNA: Doctor. Blue switches done, but they've found me.

[Clone laboratory]

DOCTOR: Now!
(The Doctor zaps the teleport with his sonic screwdriver, and Donna disappears from the spaceship just in time.)
DONNA: Have I ever told you how much I hate you?
DOCTOR: Hold on, hold on. Get off me, get off me. Got to bring the Tardis down.
(The Tardis returns to the alleyway.)
DOCTOR: Right, now. Martha, you coming?
MARTHA: What about this nuclear launch thing?
DOCTOR: Just keep pressing N. We want to keep those missiles on the ground.
DONNA: There's two of them.
DOCTOR: Yeah, long story. Here we go. The old team, back together. Well, the new team.
(Donna and Martha join the Doctor in the teleport.)
DONNA: We're not going back on that ship!
DOCTOR: No, no, no. No. I needed to get the teleport working so that we could get to

[Rattigan Academy]

DOCTOR: Here. The Rattigan Academy, owned by
(Rattigan points his gun at them.)
RATTIGAN: Don't tell anyone what I did. It wasn't my fault, the Sontarans lied to me, they
(The Doctor takes the gun and throws it away.)
DOCTOR: If I see one more gun
DONNA: You know, that coat sort of works.
MARTHA: I feel like a kid in my dad's clothes.
DONNA: Oh well, if you're calling him dad, you're definitely getting over him.

[Spaceship]

SKREE: A human female on board ship. It could only be the Doctor's work and all the teleport systems have been deadlocked open.
STAAL: No matter. Increase the ATMOS devices to maximum. Choke them. Behold, the cloneworld is born.

[Nobles' home]

(The Earth's atmosphere turns orange-brown. The gas is getting into the houses.)
WILF: Oh, my little girl. Come on, we'll be all right. We'll be all right. Donna said so. She promised. Come on, darling. It's all right.

[Academy laboratory]

(The Doctor is building a gizmo.)
DOCTOR: That's why the Sontarans had to stop the missiles. They were holding back. Because caesofine gas is volatile, that's why they had to use you to stop the nuclear attack. Ground to air engagement could spark off the whole thing.
MARTHA: What, like set fire to the atmosphere?
DOCTOR: Yeah. They need all the gas intact to breed their clone army. And all the time we had Luke here in his dream factory. Planning a little trip, were we?
RATTIGAN: They promised me a new world.
DOCTOR: You were building equipment, ready to terraform El Mondo Luko so that humans could live there and breathe the air with this. An atmospheric converter.

[Spaceship]

STAAL: Prepare to launch clone pods. We will breed across the surface of the Earth for the glory of Sontar.

[Rattigan Academy]

DONNA: That's London. You can't even see it. My family's in there.
DOCTOR: If I can get this on the right setting.
MARTHA: Doctor, hold on. You said the atmosphere would ignite.
DOCTOR: Yeah, I did, didn't I?
(The Doctor activates the atmospheric converter, and an energy pulse zooms up into the grungy clouds. KaBOOM! The Doctor crosses his fingers as the fireball spreads in the upper atmosphere.)
DOCTOR: Please, please, please, please, please, please, please.

[Spaceship]

SKREE: General Staal, sir.
STAAL: What's happening?
(The flames race around the world, consuming the gas without damaging any buildings, and leaving a clear blue sky behind. The people come out of their houses to celebrate. Captain Price kisses Colonel Mace.)

[Rattigan Academy]

RATTIGAN: He's a genius.
MARTHA: Just brilliant.
DOCTOR: Now we're in trouble.

[Spaceship]

STAAL: It seems we must revert to Basic Sontaran Stratagem One. We will ravage this planet. Prepare weapons. Wipe them out. Every last stinking human beast.

[Recreation area]

(The Doctor carries the atmospheric converter into the teleport.)
DOCTOR: Right. So, Donna, thank you for everything. Martha, you too. Oh, so many times. Luke, do something clever with your life.
DONNA : You're saying goodbye.
DOCTOR: Sontarans are never defeated. They'll be getting ready for war. And, well, you know, I've recalibrated this for Sontaran air, so
MARTHA: You're going to ignite them.
DONNA: You'll kill yourself.
MARTHA: Just send that thing up on it's own. I don't know. Put it on a delay.
DOCTOR: I can't.
DONNA: Why not?
DOCTOR: I've got to give them a choice.
(The Doctor teleports.)

[Spaceship]

STAAL: Oh, excellent.
DOCTOR: General Staal, you know what this is. But there's one more option. You can go. Just leave. Sontaran High Command need never know what happened here.
STAAL: Your stratagem would be wise if Sontarans feared death, but we do not. At arms.
DOCTOR: I'll do it, Staal. If it saves the Earth, I'll do it.
STAAL: A warrior doesn't talk, he acts.
DOCTOR: I am giving you the chance to leave.
STAAL: And miss the glory of this moment?
SKREE [OC]: All weapons targeting Earth, sir. Firing in twenty.
DOCTOR: I'm warning you.
STAAL: And I salute you. Take aim.
DOCTOR: Shoot me, I'm still going to press this. You'll die, Staal.
STAAL: Knowing that you die too.
SKREE [OC]: Firing in fifteen.
STAAL: For the glory of Sontar. Sontar-ha. Sontar-ha. Sontar-ha. (etc.)
(Rattigan is working on the teleport.)
DOCTOR: I'll do it.
STAAL: Then do it!

[Recreation area]

MARTHA: What are you doing?
RATTIGAN: Something clever.
(Rattigan teleports away.)

[Spaceship]

(The Sontarans are still chanting.)
SKREE [OC]: Ten, nine, eight, seven
(The Doctor vanishes and Rattigan appears, catching the converter control.)
SKREE [OC]: Six, five, four, three
RATTIGAN: Sontar-ha!
SKREE [OC]: Two, one. 
(The Sontaran spaceship goes KaBOOM! taking out the just launched clone pods.
The Doctor drops into the Academy teleport, breathless.)

[Street]

(Sylvia walk home with the shopping.)
SYLVIA: Morning.
WOMAN: Morning.
SYLVIA: Walked all the way. Won't catch me driving.
(The woman unlocks her car and removes the ATMOS sticker from the rear window.)

[Nobles' home]

SYLVIA: The streets are half empty. People still aren't driving. There's kids on bikes all over the place. It's wonderful. Unpack that lot, I'm going to see if Suzette's all right.
(Sylvia leaves.)
WILF: I won't tell her. Best not. Just keep it as our little secret, eh?
DONNA: Yeah.
WILF: And you go with him, that wonderful Doctor. You go and see the stars, and then bring a bit of them back for your old Gramps.
DONNA: Love you.

[Tardis]

MARTHA: How were they?
DONNA: Oh, same old stuff. They're fine. So, you going to come with us? We're not exactly short of space.
MARTHA: Oh, I have missed all this, but, you know. I'm good here, back at home. And I'm better for having been away. Besides, someone needs me. Never mind the universe, I've got a great big world of my own now.
(The door slams shut on its own and the time rotor activates, throwing everyone around.)
DOCTOR: What? What?
MARTHA: Doctor, don't you dare!
DOCTOR: No, no, no. I didn't touch anything. We're in flight. It's not me.
DONNA: Where are we going?
DOCTOR: I don't know. It's out of control! 
MARTHA: Doctor, just listen to me. You take me home. Take me home right now!