On the day of a terror attack in London, GP Mona Harcourt discovers that her brother has been kidnapped in Pakistan and his son Danny has gone missing.

After managing to contact Danny, Mona travels to Lahore to identify Kareem's body. The trip presents an opportunity to reunite with her nephew but also leads her into danger.

Mona returns to Britain and, despite being injured, is determined to investigate whether Danny is linked to Islamic radicals, but her efforts to get Danny to safety have consequences.

Mona is released from custody, and her agreement to help the police bring in Danny puts her marriage under massive strain.

When Danny is trapped in a London flat with the rest of the terror cell, Omar's attempt to rescue him compromises the police operation.