September 1940. France has fallen and London is braced for invasion. But Hitler's head of intelligence believes that only Churchill's removal will win Germany the war. At his London apartment, an old man is pushed over the banister and falls to his death. Inspector Quaid of Scotland Yard is convinced that this is a run-of the mill case of murder. But when his junior, Detective Trave, discovers that the victim was the ex-chief of MI6, he suspects a more sinister motive, and uncovers a much grander scheme by a mole inside the Secret Service to assassinate Churchill himself.