When corpses drained of blood begin to show up in a European village, town elders suspect a vampire on the loose. Policeman Karl Brettschneider (Melvyn Douglas) doubts the existence of vampires, but Dr. Otto von Niemann (Lionel Atwill) argues to the contrary. Fingers point at the village idiot, Herman Gleib (Dwight Frye), but after local vigilantes get him out of the picture, the killings continue. Brettschneider then tries to keep a cool head as he searches for possibly supernatural answers.