Antique dealer Robert Manning travels to Greymarsh Lodge to search for his missing brother, Peter. The lodge is where the Manning ancestors had lived for generations, but the owner Morley denies Peter ever stayed there. Suspicious, Robert decides to uncover the truth. That night, the villagers of Greymarsh celebrate the burning of the Black Witch, Lavinia, who had practiced witchcraft on the villagers 300 years ago. Robert discovers that Morley is a descendant of Lavinia. Professor Marshe, a local expert on witchcraft, tells Robert that Lavinia had cursed every villager responsible for her death and that many of their descendants met violent ends. The butler later reveals to Robert that his brother is dead. After Morley drugs Robert's drink, he has a strange dream where he is attacked by the dead witch, Lavinia.
Investigating further, Robert discovers that Morley is obsessed with avenging the death of Lavinia on every descendant responsible for her death. Robert is overpowered and forced to watch as Morley's niece is about to be sacrificed. Professor Marshe arrives in time to prevent her murder on the sacrificial altar. Suddenly, Morley sets fire to the house and escapes. Trapped on the roof, he transforms into Lavinia as he burns to death.