Episodes 01

Police Sergeant David Budd, an Afghanistan War veteran, is on a train to London Euston when he foils a suicide bomber’s plot to blow up the train. Due to his actions, the man and woman terrorists are arrested and taken into custody for interrogation. His heroism results in his promotion to serve on the personal detail of Julia Montague, the Home Secretary. There is tension between the two, as Montague has supported the Iraq War and War in Afghanistan and plans to update RIPA, which opponents believe will threaten civil rights. Budd’s experience as a soldier has resulted in his hostility to continued government action there. Montague’s ex-husband and Chief Whip Roger Penhaligon suspects her of exploiting the terrorist threat, and of intentions to try to replace the Prime Minister. Meanwhile, Budd struggles to deal with both his PTSD and his deteriorating relationship with his wife. Budd meets Andy Apsted, an old army friend, in the anti-war Veterans Peace Group. Apsted is disgusted with his friend’s new career.

Episodes 02

Stephen Hunter-Dunn, Director General of MI5, informs Montague of intelligence suggesting a terrorist plan to attack Budd’s children’s school in retaliation for his foiling of the train bombing. He advises her to keep it secret, fearing a member of the police might have leaked Budd’s information to the terrorists. Montague later controversially transfers investigation of the foiled bombing of the school to MI5. When a bomb detonates in the street nearby, two terrorists and three police officers are killed. Budd’s family is relocated to a safe house. He is removed from Montague’s detail, but she has him reinstated. She also arranges the offer of a place at a special needs school for Budd’s son. Returning from a COBRA meeting, Montague’s car comes under sniper fire that kills her driver, but she and Budd survive. Budd pursues and corners the sniper, who is revealed to be Apsted before he kills himself. Budd hides his relationship with Apsted. That evening, Budd and Montague act on their attraction and have sex. The next day he is instructed by Anne Sampson, Head of the Metropolitan Police Counter Terrorism Command, and his superior, CSU Lorraine Craddock, to record Montague’s meetings. They also tell him she had prior knowledge that his children’s school would be targeted.

Episodes 03

A man calling himself Richard Longcross gives a tablet to Montague, with instructions to use it to access encrypted information. Budd researches Longcross, but is unable to find his profile. With Budd serving as her driver, Montague corners the Prime Minister at Chequers, but their conversation is not revealed. Budd is interviewed by Counter Terrorism Command detectives Sharma and Rayburn, who seem skeptical of his account of the sniper attack. RIPA 18 passes the third House of Commons vote. Mike Travis, Minister of State for Counter-Terrorism, meets Penhaligon to express concern about Montague’s relationship with MI5. After Budd chokes Montague during a PTSD episode, she keeps her distance. But before Montague gives a planned speech, she tells Budd that she was informed his children’s school was a possible terrorist target. She says she wants him by her side, not because it is his job, but by choice. As she is giving her speech, Budd sees her PR advisor Tahir Mahmood outside the auditorium, but allows him in after checking his briefcase. Seconds later a bomb explodes.

Episodes 04

Knowles and Mahmood were killed in the blast and Montague is in intensive care. Travis is appointed Acting Home Secretary and transfers responsibility for investigating the bombings back to Counter Terrorism Command. The police suspect that Mahmood was responsible for the bombing, but CCTV is not conclusive that the explosion emanated from the briefcase. Budd falls under suspicion because he failed to spot the bomb when clearing Mahmood. DCI Sharma and DS Rayburn interview him and search his property. The next day, the PM announces that Montague is dead. CCTV from the House of Commons shows adviser Rob MacDonald handing Mahmood the briefcase. Before MacDonald is interviewed by police, Travis tells him to stick to their pre-arranged story. Budd attempts suicide, but fails because someone has replaced the bullets in his hidden pistol with blanks. Returning to Montague’s hotel, he discovers the security footage has been tampered with to delete Longcross’s visit. On orders from Sampson, he accompanies Rayburn to interview Nadia, the suicide bomber on the train, about who had supplied explosives to her. Nadia does not identify the bomb-maker among the pictures she is shown, which include one of Mahmood.

Episodes 05

Analysis establishes that the bomb was not in the briefcase, but under the stage. Rayburn discovers that CCTV footage from before the attack was altered, and Budd creates an E-FIT of Longcross. Apsted is identified by SO15, with his past as an army EOD officer raising suspicion that he might have been the bomb maker. Nadia identifies Longcross as the man her husband met. Budd researches the kompromat Montague was given, and ambushes Penhaligon at his constituency surgery, accusing him of trying to steal the tablet while she was in hospital. Hunter-Dunn denies any association with Longcross, but still refuses to share information with police. MacDonald reveals he and the party planned to embarrass Montague by altering her speech, but never intended physical harm. Budd meets with a gun dealer and attempts to acquire the same type of sniper rifle Apsted used. This attracts the attention of Luke Aikens, a powerful crime lord and another member of the conspiracy. When information regarding Budd’s relationship with Montague and his attempted suicide is leaked, Craddock suspends him from duty and revokes his firearms licence. He visits Montague’s flat and finds the tablet hidden in a photo frame.

Episodes 06

Aikens abducts Budd and fits him in a suicide vest with a dead man’s switch. The police are called, but they do not believe his story and instead suspect Budd’s involvement in the conspiracy due to his newly revealed connection to Apsted. Budd says that he had liked about that to avoid being a fall guy. MI5 is monitoring the scene; suspecting that he is being watched, Budd gives false information about the location of the kompromat, and MI5 sends Longcross to retrieve it. However, Budd has booby-trapped the flat with pepper spray, temporarily blinding Longcross, who is arrested. After a stand-off, Vicky runs towards Budd to prevent the police from shooting him. Still wearing the vest, Budd leads the police to his flat, where Vicky gives them the kompromat and the blank rounds that confirm Budd’s innocence. The explosives officer helps Budd disarm the vest and Budd escapes so he can prove his innocence. He discovers Craddock is Aikens’s police insider and refrains from fatally shooting Aikens. After Aikens and Craddock are arrested, Craddock confesses to leaking Montague’s movements and enabling her assassination. She also admits that she chose Budd to be Montague’s PPO because his military/PTSD background made him a perfect fall guy.

Nadia is interviewed again and reveals she lied about recognising Longcross’s E-FIT. Nadia says that she built the explosive devices herself. She remembered Budd telling her details about his children as he disarmed her first suicide vest; she passed that on for the attack on their school. The kompromat is leaked, apparently by Sampson, and she tells Budd that the Prime Minister and the Director-General of MI5 will resign. Budd starts occupational health treatment to deal with PTSD, and he and Vicky travel with their children to visit his parents.