The title says it all: This time young Dr. Jekyll (Jack Taylor), the grandson of the more famous one, must contend with a werewolf (Paul Naschy) rather than grandpa's bestial alter ego Mr. Hyde. Well, that's not quite accurate. What happens here is that the werewolf seeks out a cure for his lycanthropy from Jekyll. The good doctor pumps him full of a serum that turns the wolfman into Mr. Hyde. Even worse, this Hyde is an S&M freak, seeking out beautiful women for the purposes of bondage and torture. Jeckyll wants to put an end to all this, but he is prevented from doing so by his insane lab assistant. By 1971, baying at the moon and growing an inordinate amount of facial hair was old hat to the ubiquitous Paul Naschy.
by Hal Erickson synopsis