In medieval France, the plague sweeps across the countryside and fear-stricken peasants blame witches for the disease. Bernard de Fossey, Paul Naschy the local "witchfinder," travels from town to town on a self-styled holy mission, aided by his two lecherous assistants Nicolas Rodier Ricardo Merino and Pierre Burgot Tony Isbert, hunting down supposed witches and delivering brutal executions.
Most of the women deny they are witches, but Fossey and his henchmen torture them mercilessly until they confess, and then they are put to death in cruel fashion. The village witnesses a chilling display of fear, superstition, and power as innocent women endure coercion in the name of piety.
Catherine, Daniela Giordano, a beautiful young girl in the village, is in love with Jean Duprat Juan Luis Galiardo, who hopes to marry her. Fossey’s obsessions twist into a personal vendetta as he fixates on Catherine and schemes to remove Jean, even hiring highwaymen to ambush and kill him in the forest. That night, Catherine has a dream in which the killers are paid with coins to murder Jean, but the face of the ringleader remains hidden from her.
Catherine makes a pact with Satan, Paul Naschy, agreeing to sell her soul if he will help her avenge Jean’s death. She drifts through surreal dream sequences where she encounters Satan and the red-eyed Belphegor, who reveal that Fossey himself financed the murder of Jean Duprat. The visions blur the lines between faith, fear, and temptation as Catherine’s longing for vengeance drives her toward dangerous choices.
Catherine seduces Fossey and slyly drags him into immoral acts that backfire on him, leading to accusations of witchcraft and torture that shave his head and condemn him to death, alongside Catherine. In the finale, the film intensifies the sense of ritual and catastrophe, culminating in a fiery stake scene that echoes the shocking atmosphere of the era.
Catherine sacrifices her own life to ensure Fossey pays for his crimes, and the two are burned together at the stake in a blaze that lingers in the memory, a stark finale that casts a critical eye on zeal, power, and the cost of cruelty. The closing image lingers on the blaze and the consequences of fear-driven justice, leaving viewers to ponder the monstrous potential of zealotry when unchecked by mercy.
