Chapman offers to work as a spy for the Germans, who are at first skeptical of his motives, but because of his unique qualifications they must consider it. They eventually fake his execution and smuggle him into occupied France where, working closely with his handler, Col. Baron von Grunen (Yul Brynner), he is trained to be a spy. He becomes romantically involved with a fellow spy known only as Countess (Romy Schneider), one of the agents who first interviewed him. He is closely watched by the dour Lt. Keller (Harry Meyen), who never trusts him. They are all watched by Col. Steinhager (Gert Fröbe), von Grunen's immediate subordinate.