Based on the popular radio series David Harding, Counterspy. Howard St. John plays Harding, with actor/director Fred Sears co-starring as Harding's assistant Peters. Most of the film is carried by Willard Parker as Jerry Baldwin, a navy commander assigned to root out saboteurs in a torpedo factory. Falling in love with Betty Iverson (Audrey Long), the widow of his murdered predecessor, Baldwin is aghast to learn that Betty may be an enemy agent.