Eddie Chapman was one of the most remarkable double agents Britain has ever produced. In 1941, after training as a German spy in occupied France, Chapman was parachuted into Britain with orders to blow up an airplane factory. Instead, he contacted MI5, the British Secret Service. For the next four years, he worked as a double agent, a British spy at the heart of the German Secret Service. MI5 has now declassified all of Chapman's files, allowing the full story to be told, a unique glimpse into the psychology of espionage, with its thin and shifting line between fidelity and betrayal.