In a film that stirred up the censors, Marlene Dietrich plays a lusty gypsy named Lydia, whose caravan makes a romantic refuge for British agent .Ray Milland. Escaping from the Nazis, Agent Ralph Denistoun (Milland) and his partner arrange to meet in Stuttgart to purloin Hitler's poison gas formula. On the journey, Denistoun meets Lydia, whose uncanny knowledge of the Black Forest keeps him out of harm's way. Disguised as a gypsy, complete with glistening golden earrings, Denistoun arrives at the designated meeting place, which is glutted with Nazi soldiers. Only with the help of the extraordinary gypsy woman can he finish the mission that will make him a hero.