This lurid supernatural thriller was part of a wave of European horror films concerning demonic possession released in the wake of 1973's , and incorporates strains of a related -- and almost entirely Continental -- subgenre, the "sexy nun film." Jean-Claude Verne stars as teenaged Peter, who takes a picture of a mysterious naked woman (Mimma Monticelli) near a pastoral waterfall. When the picture is developed, the woman's image is gone, and Peter is possessed by her ghost through a cursed amulet he finds at the scene. The usual gory murders and exorcisms ensue, as well as gratuitous scenes of Satanic orgies, until Peter's sister, a nun named Elena (Patrizia Gori), re-enacts Father Karras' heroic sacrifice from this film's famous inspiration. Richard Conte co-stars with Francoise Prevost and Elena Svevo, and the music was by Giuliano Sorgini ( ). Butchered video prints are missing between five and 20 minutes.