Alan Armstrong (Kane Richmond) as the Spy Smasher is a costumed vigilante and freelance agent, not associated with the US government as the country has not yet joined its allies in World War II. After discovering information about Nazi activities in occupied France, he is captured and ordered to be executed. However, with the help of Pierre Durand (Franco Corsaro), he escapes back to the United States, meeting with his twin brother Jack (Kane Richmond). Jack is incorrectly recognized and attacked by a Nazi agent on American soil. The agent works for a sabotage leader codenamed The Mask (Hans Schumm), who operates a U-boat near the coast. Eve Corby (Marguerite Chapman) plays Jack's fiancé.