Harry Pearce is still head of the counter-terrorism department at MI5. Harry's team is transporting apprehended terrorist Adem Qasim through London when the convoy is attacked, allowing Qasim to escape and a CIA operative to be killed. When a terrorist escapes custody during a routine handover, Will Holloway must team with disgraced MI5 Intelligence Chief Harry Pearce to track him down before an imminent terrorist attack on London.