In 1454, in France, the sorcerer Alaric de Marnac is decapitated and his mistress, Mabille De Lancré, is tortured to death having been accused of witchcraft, vampirism and lycanthropy. Before they die, they curse the next generations of their executioners. In the present days (in the 70's), Hugo de Marnac, Sylvia and their friends, Maurice Roland and his beloved Paula, go to a séance session, where they evoke the spirit of Alaric de Marnac. They decide to travel to the Villas de Sade, a real estate of Hugo's family in the countryside, to seek a monastery with a hidden treasure. They find Alaric's head and the fiend possesses them, bringing Mabille back to life and executing the locals in gore sacrifices. After the death of her father, Elvira recalls that he has the Thor's Hammer amulet hidden in a well; together with Maurice, they try to defeat the demoniac Alaric de Marnac and Mabille.