Nick Lassiter (Tom Selleck) is a gentleman thief in 1939 London, England. He is arrested by the police after breaking into a London mansion and, after being a member of a phony police lineup in which he is positively identified by a law enforcement plant, British law enforcement and the FBI blackmail Lassiter to break into the German Embassy and steal $10 million in Nazi diamonds from a German spy (Lauren Hutton), but first he must locate their hiding place. The gems are en route to South America and will be sold to help finance Adolf Hitler military buildup.