After injecting new life into classic movie monsters Dracula and Frankenstein, Hammer Studios apply their Gothic touch to another monster genre with this excellent, stylish piece -- probably the best of the old school (i.e. pre-Rick Baker) man-to-wolf transformation films in the mold of Universal's The Wolf Man. The title curse surfaces when a mute servant girl bears a child on Christmas day after being raped by a bestial madman and first shows itself at the infant's christening, whereupon the holy water begins to boil. Things go downhill from there, as young Leon's development is marred by savage, violent behavior during a full moon. Upon adulthood, Leon's (Oliver Reed) only relief from his murderous impulses comes from the love of Christina (Catherine Feller)... but he soon begins to fear that this cannot contain the beast within. Liberally based on Guy Endore's The Werewolf of Paris (here relocated to Spain), this film represents Hammer at their early best, building tension through mood and character (Reed turns in a bravura performance) and saving the effective monster transformation for the climax.