A scientist working on cures for rare afflictions, such as a bone softening agent made from molds to allow him to correct the spinal deformity of his nurse, finds the physical causes of lycanthropy in wolf-man Larry Talbot and of vampirism in Count Dracula, but himself becomes afflicted with homicidal madness while exchanging blood with Dracula.
John Carradine
Onslow Stevens
Lon Chaney Jr.
Martha O'Driscoll
Jane Adams
Lionel Atwill
Glenn Strange
Ludwig Stössel
Skelton Knaggs
Joseph E. Bernard
Dick Dickinson
Harry Lamont
Robert Robinson
Anne G. Sterling
Fred Cordova
Carey Harrison
Gregory Marshall
Beatrice Gray