Wheelchair-bound mad scientist Dr. Durea (J. Carrol Naish), the last descendant of the original Victor Frankenstein, takes to murdering young girls for experimentation in hopes of perfecting a blood serum of his own creation with help from his mute, simple-minded assistant Groton (Lon Chaney, Jr.). Count Dracula (Roger Engel (producer Al Adamson's stockbroker) listed in the film's credits under the pseudonym "Zandor Vorkov") comes to the scientist, promising to help him revive Frankenstein's monster (which he has exhumed from its secret grave in Oakmoor Cemetery) in return for Durea's serum, which he hopes will grant him immunity to sunlight.