Three children of the Merrye family live in a decaying rural mansion with their protector and chauffeur, Bruno (Chaney). The children suffer from "Merrye Syndrome", a genetic affliction unique to members of their family, which causes them to mentally, socially and physically Atavism, starting in late childhood. Two distant relatives arrive with their lawyer and his secretary in order to examine and claim the property as rightful heirs. Bruno's shaky control over the children deteriorates; murder, chaos and insanity ensue.