Successful GP Mona Harcourt receives word that her brother has been kidnapped in Pakistan while en route back to the UK. The family's shock is not made any easier as it emerges her brother's teenage son Danny has aroused the interest of the police counter-terrorism unit following his disappearance from university, so Mona attempts to find Danny before the police do.

Having secretly got in touch with Danny in Lahore, Mona is approached by police counter-terrorism chief Vivien Barnes to travel to Pakistan and identify Kareem's body. Despite her husband Guy's resistance, Mona immediately flies out and tries to make contact with her nephew, but when she absconds from a Lahore mortuary to attend a rendezvous with Danny, the GP's search leads her to a remote part of the city and grave 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, but the fallout from her actions at home is disastrous, and her marriage is under more strain than ever.

Omar attempts to step in and rescue Danny but puts the entire counter-terrorism operation in danger. With the terror cell compromised and off-grid, the police's trust in Danny is severely damaged in the process.

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.