GP Mona Harcourt discovers that her brother has been kidnapped in Pakistan.
Having contacted Danny in Pakistan, Mona travels to Lahore to identify Kareem's body. The trip presents an opportunity to make contact with Danny but also leads her to danger.
Mona returns to the UK and is determined to investigate Danny's suspected links to radical Islam despite her injuries, but her efforts to get Danny to safety on the day of Kareem's funeral have unexpectedly dire consequences for the family.
Mona is released from custody and agrees to become a tasked witness and help the police bring Danny in as an informant. However, the fallout for her actions at home is disastrous and her marriage is under more strain than ever.
Omar's attempt to rescue Danny puts the entire counter-terrorism operation in danger, compromises the terror cell and takes them off-grid, and damages the police's trust in Danny.
Barnes and the counter-terrorism unit face a race against time to foil the imminent terror attacks. Their challenge is made even greater still as Mona and Danny are still trapped within the terror cell and their lives are at risk.