When a scientist returns from Tibet, where he was transformed into a werewolf, he becomes the unwilling henchman of a fellow researcher who's developing a substance that will allow her to control the minds of others. Meanwhile, prisoners of the madwoman amuse themselves in the castle dungeon and a masked phantom roams the halls. José María Zabalza directs this wonderfully campy horror flick from Spain that stars Paul Naschy and Perla Cristal.