Episode 4

Two former inmates are released from jail. One is an undercover MI5 asset and the other is an impressionable wannabe suicide bomber who has been radicalised in prison. They are set to launch an attack somewhere in London, but our team must time it right and step in at the eleventh hour to prevent a massive loss of life.

A controversial imprisoned religious leader has his appeal for parole rejected. Shortly afterwards, two prisoners are released from the same jail. They are on a suicide mission to avenge the religious leader's rejected appeal. It turns out that one of them, Ashur, is an MI5 asset who has been passing on useful intelligence from inside the prison. Erin and the team make the decision to keep him working for them whilst they work out the target for the attack. They promise to pull him out before it gets too dangerous. Ashur is an honourable man who hates the fundamentalism preached in UK prisons. He is committed to MI5 on the condition that they will send his daughter over from Karachi to live as a UK citizen. But things go wrong when both Ashur's and Erin's daughters are kidnapped by the bombers and used as collateral. Harry has to decide whose life is more important. Will he choose to save the life of his section chief's daughter, or the lives of hundreds of members of public?

Harry's suspicions of CIA deputy-director Jim Coaver are compounded when a credible connection is made between him and Gavrik's assassin and to the intelligence leaks. At the same time, a startling attempt is made on Elena's life. Ruth tells Harry about the Home Secretary's approach to work for him. To her surprise, Harry tells her to leave section D as he doesn't want her to witness what he is about to do next...