Lt Will Hoffman and his date, Nisha Townsend, are drinking and dancing at the Vita Futura nightclub when Hoffman spots a commotion; people are trying to run away from a man who appears to be standing still on the dancefloor. Hoffman orders Nisha to get out, but as she heads for the exit, the man on the dancefloor shouts that he’s doing this for his people and triggers a suicide bomb, blowing up the club. Hoffman, dazed and half buried beneath the rubble, is unable to respond when a man identifying himself as Sgt Fleming of the Metropolitan Police enters the ruins with his men. Nisha calls out for help -- and to Hoffman’s horror, they shoot her dead before fanning out through the ruins of the club, killing all other survivors they find.
Scott Christie reports the bombing on the 9:00 news, along with the signing of the Euro Combine treaty, increased racial tensions in Southend, and the worsening flu epidemic in the Home Counties. Elsewhere, Colonels Dalton and Chaudhry have gone out to a pub called the White Rabbit; they are no longer so wary of each other, as Dalton is coming to accept the weird incidents UNIT deals with and Chaudhry is coming to accept him as her CO. She is still determined to find out what happened to the missing Colonel Brimmicombe-Wood, however. Their night out is interrupted by the television report of the bombing, and Chaudhry then receives a phone call from Hoffman himself, who tells her that people claiming to be the police are shooting the few survivors of the bombing. Fleming spots Hoffman trying to slip away and gives chase; Dalton and Chaudhry try to get to him, but they’re on the opposite side of the river. As he flees, Hoffman reports that the bomber was a young Scotsman in his early 20s, wearing a blue T-shirt with a silver pattern. Fleming catches up to him and demands to know who he’s talking to, and Hoffman drops the phone in the river; now, if Fleming wants to know who he’s working for, he’ll have to keep Hoffman alive. Sadly, Fleming decides he doesn’t need to know all that badly, and he shoots Hoffman and walks off as Hoffman’s body falls into the river.
The PM and his deputy, Meena Cartwright, are racing towards 10 Downing Street; they don’t know who was responsible for the bombing, but have received intelligence reports that it won’t be an isolated incident. Even as they speak, a young woman blows herself up on the Westminster tube station platform, shouting that she’s doing this for her people. Above ground, smoke pours up out of the Underground as Dalton tries to pull the grief-stricken Chaudhry together. Francis Currie then calls Chaudhry’s cell phone, claiming that has information on the bombings but will only trust it to her. Chaudhry, though still shaken by Hoffman’s death, agrees to meet with Currie alone at Westminster Abbey. Dalton returns alone to UNIT HQ and tries to identify the nightclub bomber from the club’s CCTV footage. He hesitates a moment when he sees Hoffman and his date alive and enjoying themselves on the tape, but continues with his work and identifies the bomber, based on Hoffman’s description, as a young man named Marcus Hussey with no previous history of violence. However, he then sees a TV news report claiming that the bomber was a Muslim student named Abdul Malik Hassib, and realises that the “policemen” were killing survivors at the club so nobody could idenfity the real bomber.
The PM’s attempt to make a calming public statement is interrupted by reporters, who bombard him with questions, demanding to know whether the explosions were racially motivated and if there will be more to come. Flustered, the PM cuts the press conference short and retreats back into 10 Downing Street. His press secretary, Philip Kirby, has not yet arrived, and when he finally does, the PM orders him to impose a press blackout before the media starts speculating and blaming Muslim extremists without evidence. Kirby points out that they can only silence the BBC, not the independent broadcasters. Meena suggests triggering the access overload system, which will stop the civilian use of mobile phones and leave the airwaves clear for the emergency services, but Kirby patronisingly claims that this will increase public panic. The PM decides not to trigger this system just yet, and demands that Kirby contact UNIT; however, Kirby claims that nobody there is answering his calls. Meanwhile, the story is sweeping across the media; horrific scenes are beign played out on TV screens across the country and pundits are analysing motives for the attacks, suggesting that Britain is seeing repercussions for its military actions in Iraq. Albion Hospital has been overwhelmed with the injured, and another attack on Holloway Prison has set free many potentially dangerous inmates...
Westminster Abbey is full of frightened people seeking shelter somewhere familiar and traditional. When Chaudhry arrives, Currie takes her to a secluded room where they can speak privately, but then attacks her, claiming that he’s doing this for his people. Chaudhry kicks him somewhere painful, knocks him out, and contacts Dalton to report what’s happened. Currie didn’t seem himself, as if he’d been brainwashed somehow -- and Dalton in turn reports that the real nightclub bomber was a young man with no history of violence. Chaudhry takes Currie back to UNIT HQ for interrogation, and on the way back, he revives -- but has no memory of having attacked Chaudhry. Meanwhile, the death toll continues to rise, the government closes down all flights out of the city, and the media reports that London is effectively under siege.
Kirby insists that the situation will continue to escalate unless the PM puts troops on the streets to maintain order -- but the troops he has in mind are ICIS, and Meena is definitely opposed to this. The PM does take Kirby’s military experience into account, but refuses to declare martial law unless he has no other option. While the PM is speaking with the chief of police, Kirby acidly suggests that Cartwright probably understands the bombers’ motives more clearly than he does. All foreigners are the same to Kirby, and he’s convinced that Cartwright, a female Indian, got her job through affirmative action rather than because she’s actually very good at it. Meena storms out on Kirby in disgust, unaware that the pathetic old man is far more dangerous than she’s giving him credit for. The PM assures her that he’s just playing weak so that Kirby will underestimate him, but as they speak, Meena receives a call on her cell phone. She seems distracted when she hangs up, but assures the PM that she’s just heard that her husband and children are safe... with their people. Meanwhile, Kirby makes a phone call to Andrea Winnington; his voice is smooth and seductive, assuring her that it’s not racist to mistrust those who are different from one’s own kind, and urging her to do something for her people.
At UNIT HQ, Chaudhry and Dalton interrogate Currie, who has no memory of phoning Chaudhry, let alone trying to kill her. However, when he checks his mobile phone, he finds that it was indeed used to place a call to Chaudhry. Shocked to learn that Will Hoffman has been killed, Currie tries to remember what he was doing before he woke up in Chaudhry’s car, and remembers working late at his office in Planet 3, where he moved after the BBC decided his reporting style was too sensationalistic. He vaguely recalls getting a phone call telling him to do something for his people, and when Dalton hacks into his access provider’s records, he finds that Dalton was called from a government-sponsored quit-smoking helpline. Whoever misidentified the nightclub bomber as a Muslim is obviously trying to increase racial tensions and plunge the country into war -- and if the persons responsible are using government help lines to programme sleeper agents, then anybody in the country who’s ever phoned a help line could become a potential killer.
Chaudhry and Currie realise that the people behind the attacks are trying to make the maximum amount of media impact, just as the collapse of the Twin Towers horrified the world at least partly because it was such a striking visual image. Vita Futura was targeted because it symbolised Britain’s new multiculturalism and the end of Empire; the bombing in the Underground, however, will have terrorised more people, as anyone in London could have been a victim. If tonight’s attacks are meant to escalate, then the next will occur live on television. Even as Chaudhry speaks, Meena Cartwright emerges from 10 Downing Street and informs the press that her husband and children have been kidnapped and will be killed in retaliation for tonight’s attacks unless she obeys the kidnappers’ instructions -- and, claiming that she’s doing this for her people, Meena shoots herself in the head live on TV. The BBC cuts back to Scott Christie, but as the stunned newsreader tries to anchor these events, another suicide bomber blows himself up in the middle of the studio, knocking the BBC off the air.
Furious, Chaudhry vows to put an end to tonight’s horrors -- but Dalton claims that the PM’s press secretary, Philip Kirby, keeps putting him on hold. Chaudhry realises that this is not normal behaviour on a night like tonight, and as press officer, Kirby would be in a position to control both the media and the government help lines. She then learns of the attack on Holloway Prison, and realises that it’s possible that Andrea Winnington has escaped -- and the ICIS captain no doubt still bears a grudge against Chaudhry and Currie.
Dalton sets off for 10 Downing Street to speak to the PM in person, while Chaudhry looks into Kirby’s background for any possible connection to ICIS. Currie offers to help, not for the sake of the story, but because he can see how upset Chaudhry is over Hoffman’s death. Chaudhry soon discovers that Kirby was discharged from the army after a court-martial found him guilty of abusing prisoners in Iraq, but he then used his family connections to get a nice, safe desk job as the government’s press officer. This still doesn’t explain how he could have acquired the technology to brainwash innocent people over the telephone, but if he has a connection to ICIS, perhaps they supplied him with captured alien technology -- which would explain why he wanted Chaudhry, and thus UNIT, out of the way.
Currie contacts his co-worker George at Planet 3, and has him go through the stories that the government has prevented them from releasing. He thus learns that Andrea Winnington is Kirby’s illegitimate daughter, the result of an affair with his PA during the 1980s. Chaudhry wonders why Dalton didn’t know this if he’d served with her, and, worried, tries to call him; however, he does not answer his cell phone, and while Chaudhry is distracted, Winnington herself enters the room and knocks Currie out. Winnington’s father called Dalton on the phone earlier, and Dalton left the door open on his way out of UNIT -- and he’s now heading for 10 Downing Street to deal with the PM. Winnington has apparently come to UNIT seeking revenge becase Chaudhry sent her to jail for standing up for what she believed in... but to Chaudhry’s surprise, instead of shooting her, Winnington gives Chaudhry her gun and challenges Chaudhry to stand up for her own beliefs by killing her.
Chaudhry struggles to resist her anger, but Winnington provokes her by reminding her that Winnington, her father and ICIS are responsible for Will Hoffman’s death. Fortunately, Currie revives, sees what’s happening and intervenes, and in the ensuing scuffle, Chaudhry accidentally shoots and injures Currie while Winnington falls and knocks herself out. Currie reminds Chaudhry that UNIT would be destroyed if its public face was seen to commit cold-blooded murder, which is why Winnington was sent here to die. Chaudhry binds Currie’s injured wrist and borrows his voice recorder, and then sets off to 10 Downing Street via helicopter, taking Winnington in order to keep an eye on her. Winnington revives on the way, and like Currie earlier, has no memory of what she did while brainwashed. The city is in flames as panic and riots spread, and Winnington, who truly believed that she and ICIS was acting in the best interests of their country, is horrified to see what’s happened as a result.
The PM is in shock following Meena’s suicide, and Kirby presses him to declare martial law before it’s too late. Race riots have broken out all across the country; Bradford has become a no-go area for white people, and elsewhere, an angry mob has set fire to a mosque in which women and children have sought shelter. Dalton then arrives at 10 Downing Street, distracted and unsure what he’s doing, but believing that he’s acting for the good of his people. When the PM turns to Dalton for advice, Dalton tells him that martial law is indeed the only option and that ICIS must be sent out onto the streets. The PM reluctantly signs the authorisation papers, and once he’s done so, Kirby orders Dalton to shot him. As Dalton turns his gun on the terrified PM, Kirby calls ICIS to send in the troops -- and in passing, he inquires after Brimmicombe-Wood’s health. In the streets outside, ICIS troops fan out and begin to quell unrest by firing on the civilian mobs, as well as the reporter unlucky enough to catch their actions on camera.
Chaudhry lands her helicopter outside Number 10, and forces her way inside, using Winnington as a hostage. Dalton has not yet shot the PM, but he is having trouble resisting his brainwashing. Chaudhry threatens to shoot Winnington unless Kirby orders Dalton to lower his gun, but Kirby refuses, as his daughter has clearly failed him yet again. Chaudhry thus turns to Dalton, urging him to remember his training and recite a familiar nursery rhyme to regain control of his mind. As he recites London’s Burning, Winnington demands an explanation from her father, and is horrified to learn that Kirby really is responsible for the atrocities she’s seen tonight -- and he’s proud of it, as he truly believes that he’s fighting a war to keep Britain pure.
Dalton breaks his conditioning and turns his gun on Kirby, but Kirby remains unapologetic. This plan has been in place for a long time, and Kirby triggered it when he decided that the PM had sold out the country by signing the Euro Combine treaty. He is proud of driving Meena to suicide, as he claims she was making the place dirty. Chaudhry has recorded his entire confession on Currie’s voice recorder, however, and she hands it to the enraged PM, who vows to shut down ICIS completely and broadcast Kirby’s confesion on every available media outlet so the public will understand how they’ve been manipulated. Kirby remains confident that others will pick up where he left off; as evidence, he points out that while the public face of UNIT is a female with a foreign name, the real commanding officers are private-school men with solid British names like Ross Brimmicombe-Wood or Robert Dalton. But Dalton reveals that he recently learned the origins of his own name, and just to show how petty and ignorant Kirby’s beliefs are, the Daltons originated in North Germany.
All seems resolved, except for the nature of the device Kirby used to brainwash his sleeper agents; he has no idea what it was, only that it was provided to him by ICIS. Dalton frisks Kirby in case he’s carrying anything else dangerous -- and sadly, he is. He’s not just willing to kill for his beliefs, he’s willing to die for them, and in frisking him, Dalton activates the bomb in his suit pocket. It’s equipped with both a timer and a dead man’s switch, so it’s going to explode in any case and will only explode sooner if Dalton lets go. Realising that he can’t escape, Dalton orders Chaudhry to get out and take Winnington with her, and the grief-stricken Chaudhry realises that she has no choice but to do so. In the corridor outside, however, Winnington turns on Chaudhry, knocks her senseless and flees for the exit. Chaudhry recovers within seconds, but as she flees for the exit, the bomb goes off, killing Dalton and Kirby and demolishing Number 10. Winnington watches from a distance, confident that all her enemies are now dead...