All-purpose Columbia contractee Bruce Bennett (formerly college athlete Herman Brix) was awarded a leading role in the wartime "B" U-Boat Prisoner. Bennett plays merchant seaman Archie Gibbs, who manages to survive when his ship is torpedoed by a German submarine. Disguising himself in the uniform of a dead Nazi spy, Gibbs is picked up by the Nazi U-boat. He manages to convince the German sailors that he's the spy, and in this guise he tries to rescue a group of captured Allied scientists. Already unbelievable, U-Boat Prisoner journeys into the Twilight Zone during the climax, with Gibbs single-handedly incapacitating the submarine crew and rescuing the prisoners. Incredibly, the film was based on a true story, written by the real-life Archie Gibbs!