Harry and Erin kidnap Coaver. A CIA team arrives to collect him, but they turn out to be imposters.

Harry, Erin and Dimitri kidnap Coaver. During an interrogation, he insists he did not pose as Harry, nor order the attack on Elena. By pressuring the Home Secretary, the Americans learn of Coaver's location, and a CIA team arrives to collect him, but after they depart another CIA team arrives; realising the first team were imposters, the MI5 agents give chase. The imposters throw a beaten Coaver from their vehicle, and a dying Coaver tells Harry that his laptop contains the answers he seeks. Arriving after Coaver's death, the CIA team blame Harry. Harry later meets with Elena, confiding that he now believes her husband to be the mole. When Gavrik visits Harry later, he reveals he always knew Harry ran Elena, but has no interest in killing his wife. Harry convinces Ruth to steal Coaver's laptop from the United States Embassy, but she is intercepted by Sasha before she can give it to Harry, and Sasha learns from it that Harry is his biological father. Meanwhile, Section D believe that the fake CIA agents are pa

An imprisoned Islamic extremist leader appoints two followers to commit a revenge suicide mission.

When the parole of Zubier Al-Saad (Jeffery Kissoon), an Islamic extremist leader is turned down, he appoints two recently released inmates to commit a revenge suicide mission. One of those released, Ashur Mohali (Asif Khan), is an asset from the prison who passed on information to Section D. He agrees to help Erin stop the upcoming attack on the condition that his daughter be given British citizenship. However, his handlers decide to kidnap her to ensure the attack succeeds; Ashur is now committed to the cause for his daughter's safety. Section D later learns that the attack will take place on Trafalgar Square. When Erin confronts him, she learns the handlers also has her daughter, Rosie. If the attack fails, she will die; Dimitri is able to kill the handler as Ashur is killed by CO19. Meanwhile, Harry must find incontrovertible proof against Coaver. He and Ruth use Elena and Sasha as bait to get to Coaver, but find the mysterious woman instead. Later, Ruth tells Harry about the offer from Towers; he encourag

Trace amounts of radioactive material has been found at Heathrow Airport. Section D find that known anarchist Johnny Grier (Mel Raido) is in the city, who is believed to be making a dirty bomb in London. To get to him, Dimitri Levendis (Max Brown) is assigned to honeytrap his sister, Natalie (Georgina Rich), via Internet dating. Section D follows him to a cell, who plans to attack the Velanon Group, a financial company who made millions from a nuclear disaster. When Dimitri confronts him, Grier reveals he thought he was smuggling heroin to the country, and is not part of the bomb plot. Reluctantly he agrees to help; they find a van, only to find it empty; Grier double crossed them. He intends to assassinate Velanon's CEO using the radioactive powder. Dimitri fails to stop him, and the building is evacuated. Meanwhile, Towers offers Ruth a promotion to his security advisor, leaving the Grid and MI5. Harry's suspicion into Coaver has been solidified, especially after Calum found what Tariq found before his deat

Section D finds that known anarchist Johnny Grier is in the city and he may be making a dirty bomb.

On his way to MI6, Calum Reed (Geoffrey Streatfeild) is mugged, and his laptop containing the identities of five high level assets is stolen, one of which is Martha Ford (Lydia Leonard), who is close to one of Gavrik's companies. Several attempts to find the muggers prove difficult as they are highly resourceful. They manage to decrypt the first file and leak it to the Internet; asset one John Grogen is found dead. Martha's identity is leaked next, though Erin is able to bring her to a safe house before she can be killed by the Russians. However, Erin is later ordered to break all ties with her under the pressure from Gavrik. Harry meets with Elena to tell her that somebody is posing as him. He later asks Ruth to look up Central Intelligence Agency (CIA) deputy director and Cold War colleague Jim Coaver (William Hope), believing he is the imposter. After returning home Tariq Masood (Shazad Latif) discovers the identity of one of the muggers. However, he realises they are on to him, and tries to get the intel

Calum Reed is mugged and his laptop containing the identities of five high level assets is stolen.

The murder of his friend Max Witt leads Harry Pearce into a plot involving Russia and the Chechens.

Harry leads a manhunt to find and capture Lucas, and hires a specialist, Alec White.