Spanish horror auteur Paul Naschy (aka Jacinto Molina) takes a crack at the demon-possession subgenre with this dull rip-off of The Exorcist. The story involves a young woman's unknowing participation in a Satanic ceremony which causes her to be possessed by the vile spirit of her late father. She promptly begins exhibiting the standard symptoms -- guttural curses, projectile pea-soup vomiting, and so on -- even twisting the heads of a few people 180 degrees. Naschy appears as the village priest summoned to perform the rites of exorcism, and must fend off the possessee's lewd advances before casting the unclean spirit out of her body... and into the family dog. Although certainly as silly and derivative as it sounds, this is not goofy enough to suffice as enjoyably bad cinema, and tired pacing takes all the punch out of the occasional gruesome shocks.