During a handover to the head of counter-terrorism of MI5, Harry Pearce, a terrorist escapes custody. When Harry disappears soon after, his protégé is tasked with finding out what happened as an impending attack on London looms, and eventually uncovers a deadly conspiracy.

Renowned British dressmaker Reynolds Woodcock comes across Alma, a young, strong-willed woman, who soon becomes a fixture in his life as his muse and lover.