1940s sci-fi horror. When experimental doctor Alfred Morris (George Zucco) falls for his medical student Ted (David Bruce)'s girlfriend, singer Isabel (Evelyn Ankers), he decides to use an ancient poisonous gas to turn his assistant into a mindless ghoul so he can pursue the young woman. As they join her on a performance tour, Alfred keeps Ted alive with human hearts and also plans to use him to kill off Isabel's pianist Eric (Turhan Bey), who she appears to have romantic feelings for. As Alfred's victim count rises, a reporter and the police begin an investigation but suspect Isobel to be the killer. Will Alfred get away with his horrific crimes?