Early in the Second World War, debonair safecracker Eddie Chapman (Christopher Plummer) blows open a wall safe. Outside, a car is backfiring repeatedly and a marching band is passing, which mask the blast. Chapman casually removes some jewels from the safe and examines them for the choicest items. He leaves a card in the safe complimenting its owners for being victims of the "Gelignite Gang". The gang pulls off a series of heists before Chapman is caught while on holiday on the island of Jersey, where he is imprisoned. After ten months, he sees German soldiers landing outside the prison and learns that war has broken out.