A troubled couple and their blind daughter come to Italy to visit a 12th Century castle they've inherited. Soon they are plagued by unexplained noises, mysteriously broken objects, and the daughter's claims of an unknown nocturnal visitor to her bedroom. When the housekeeper and a local prostitute and are discovered savagely murdered in the castle's dungeon, John must unlock the castle's secret to save himself from jail and his family from the castle's secret inhabitant...