Robert Hossein, Marina Vlady, Robert Le Beal. A brilliant "little" spy film. Hossein and Vlady play mysterious characters who meet up one night in a lonely cabin in the wilds of Normandy. They are both spies, but whom do they work for-the Allies or the Nazis.

At the end of the Great War, Arsène Lupin resumed his adventurous life. Theft of three paintings committed by an adversary leads him to the treasure of the Golden Fleece.