Six months after the rage virus was inflicted on the population of Great Britain, the US Army helps to secure a small area of London for the survivors to repopulate and start again. But not everything goes to plan.

[after being scared by Doyle]
Flynn: Doyle, you bastard!
Doyle: Boy, I've never seen you get so white.
Flynn: Come on!
Doyle: Dude, good morning!
Flynn: Get the fuck out of here, man. I'm having all good dreams.
Doyle: Yeah?
Flynn: Sunday afternoon, clear blue skies. I'm laying in bed with my wife and... now I'm back in this shithole.
Doyle: I know, man. I had that same dream about your wife.
Doyle: Be my shadow, that's it.
Rooftop Soldier: Doyle! I got 2 fuckers on me! DOYLE!
Flynn: Where's Doyle?
Tammy: It's... just us.
DLR Soldier: We are headed for the green-zone, our area of security and reconstruction, designated as District One. District One is located on the Isle of Dogs. Although the Isle of Dogs is completely safe, the surrounding area of London is not. There are a large number of bodies still left to be cleared from the original outbreak of infection. Rats and wild dogs are prevalent, as is disease. New arrivals are reminded, for their own safety, it is absolutely forbidden to cross the river and leave the security zone. You will be joining 15,000 civilians who are already resident in District One. As we approach your new home, you will notice a dramatically increased military presence. The U.S. Army is responsible for your safety. We will do everything we can do to make your repatriation as easy as possible. Inside District One, however, we believe you'll be pleasantly surprised. We have hot and cold running water, 24-hour electricity, a medical center, a supermarket, and even a pub.
Doyle: Did I hear that code red or am I losing my shit?
Scarlet: It all makes sense. They're executing code red. Step 1: Kill the infected. Step 2: Containment. If containment fails, then Step 3: Extermination.
Scarlet: You look a little pale.
Doyle: Blood makes me nauseous.
Scarlet: Who are you?
Doyle: Sergeant Doyle, Delta Rooftop Unit.
Scarlet: Why aren't you at your post?
Doyle: Why aren't you?
Scarlet: [upon examining Andy's eyes] Green and brown. Interesting iris variation. It's usually hereditary. Do one of your parents have the same?
Andy: My mother, she did.
Scarlet: How old are you, Andy?
Andy: Twelve.
Scarlet: I think that makes you the youngest person in the entire country. Well, your blood pressure is A-OK and you're negative on any serious disease or afflictions. I think you're okay to come in. Welcome back to Britain.
Alice: Don... Help us... Don... Help us
[last lines]
French radio voice: We need your help.
Andy: Tam, am I one of them?
Tammy: No.
Flynn: Having fun down there Doyle?
Doyle: Kiss my ass! This is the worst combat I've ever seen. Where's the fucking combat?
Rooftop Soldier: Give me something to shoot.
Flynn: Too easy. Medical sector, east side, fat guy, jerking off in the toilet.
Rooftop sniper: Ah... bug nuts, I saw him yesterday.
Soldier: I don't see him. Where is Fester Fuck nut?
Rooftop Soldier: There, look! Bald guy with his dick in hands on the 20th floor.
Andy: I saw Dad.
Tammy: Dad? Where?
Andy: Tam, he's one of them.
Doyle: [seeing a plane arriving] Welcome to London.
Doyle: I got some strays.
Flynn: Dogs?
Doyle: No, puppies.
Tammy: So what do you do here, dad?
Donald Harris: What do I do? I'm a section officer. I keep the lights on, the water running, the heat running. See, that's what this says.
[shows his kids his security card]
Donald Harris: Triple A - "access all areas". That's me. I basically run the place, you know?
Tammy: Well, you're the caretaker really, aren't you?
[Don locks his kids inside a revolving door, then releases them with his security card]
Donald Harris: No, I run the place.
Tammy: You said you saw mum die!
Stone: Abandon selective targeting. Shoot everything. Targets are now free. We've lost control.
Donald Harris: Your mum and I were hiding in a house. A wee cottage. There was an old couple that owned it. And they were there, too. Three other people. And we were, uh... just trying to stay alive, I suppose. We were doing okay for a while. And then we were attacked. They came in through the kitchen window. They were really fast, you know? Chased us. Chased your mum. And we were trapped. Trapped in the bedroom. I... I seen them... biting. I couldn't do anything. I tried to go back. She was already gone. She was already gone.
Andy: Was there nothing you could do?
Donald Harris: No, there was nothing I could do. I managed to get away. Just running, running, and running. I got to this military camp. And you know the rest, you know, I've been in quarantine waiting for you guys to come back.
Tammy: We're just happy you're still alive.
Flynn: [talking over the radio] Doyle, come in.
Doyle: Flynn, go.
Flynn: Doyle, where the fuck are you man?
Doyle: Ground level, District One.
Flynn: Shit! Closed frequency.
Doyle: Copy that.
Flynn: What the fuck are you doing there? Listen to me, you've got some serious shit coming your way.
Doyle: We've already got some serious shit.
Flynn: No. I'm not fucking playing - this is worse. The air cav; they just got their orders. They're firebombing all of District One.
Doyle: That was fast.
Flynn: Outbreak is totally out of control. They're taking no chances. So unless you are out of the target zone, you are getting cooked, you got me?
Doyle: How long we got?
Flynn: They're already on their way. You got four minutes, tops. But listen, I got some clear landing ground at Regents Park. That's the pick-up point. Got it?
Doyle: I'll be back in touch.
Flynn: Hey Doyle, you fucking better be.
Alice: Who were chasing you?
Boy in Cottage: My mum, my dad... They're trying to kill me. There's others too.
Donald Harris: How many?
Boy in Cottage: Loads.
Tammy: Daddy! No!
Donald Harris: We'll be moving to our new house soon, a couple of months, in fact.
Tammy: A new house?
Donald Harris: Yeah. Listen, I hope you guys understand, um... we're not going to be able to go back to your old house. It's outside the security zone, and anyway, I don't think I'd want to go back there, even if I could.
[first lines]
Donald Harris: What are you going to cook?
Alice: Your favorite.
Donald Harris: What, again?
Scarlet: Have you come in contact with... the infected?
Rooftop Soldier: I don't see who's a target.
Stone: Clear channels to Control. Control One this is General Stone. All forces under my control prepare to execute "Code Red" on my command.