Carl Becker, a young attorney becomes a counter espionage agent after an agent friend of his is murdered. He doesn't realize that the girl, Paula Fengler, with whom he is deeply in love, is a member of a clever group of Nazi spies led by Dr. Woolford. He learns her true identity, and arrests her and traps the entire gang at the same time. The information he has allows a U.S. patrol boat to sink a Nazi submarine that had been offshore waiting for instructions from the saboteurs.