Trivia

This was the first Italian made horror film of the sound era.

Riccardo Freda made the film on a bet to producers that he could complete in 12 days. After day 10, Freda realized that the film couldn't be finished on-schedule. After his requests for an extension were denied, cinematographer Mario Bava re-wrote the script so that the film could be finished in two days, and directed the remaining scenes himself.

Mario Bava and Piero Regnoli's last-minute rewrites changed many elements of the original story out of necessity. The journalist Pierre Lantin was originally a supporting character, but was made de facto protagonist because many of the other principal players were no longer available. The henchman Joseph Signoret was originally supposed to be a corpse reanimated by Dr. Du Grand with a replaced head, but was changed to a simple heroin addict, because the actor playing Du Grand was one of the absentees. His original backstory is still alluded to by the visible scar around his neck.

The character of the Countess Du Grand is based on Elizabeth Báthory, a 15th and 16th-century Hungarian noblewoman and serial killer who killed hundreds of young women and bathed in their blood in a vain attempt to prolong her youthful appearance.

Film debut of Al Lewis, who would be best known for playing the vampire Grampa, on The Munsters (1964). He appears (uncredited) in additional scenes shot for the film's re-titled and re-edited American release.

Riccardo Freda: autopsy doctor