Safecracker Eddie Chapman is languishing in prison on the island of Jersey when the Nazis arrive. An adept manipulator of situations, Chapman convinces the Germans to use him to spy on the British. And when the would-be traitor arrives home, he convinces the English to use him as a double agent -- in exchange for a full pardon.

During the second world war, two British officers, Brand and Leith, who have never seen combat, are assigned a vital mission. Their relationship and the operation are complicated by the arrival of Brand's wife, who had a tryst with Leith years earlier.