Ellen has been taking care of her insane younger sister Cissy ever since their explorer father died. When Cissy's pet ape dies in their mansion's dungeon and Ellen finds a boyfriend, Cissy's incestuous desire for her sister turns deadly.
Two strange sisters live in a crumbling mansion, where they keep a pet ape, which belonged to their late father, locked in a cage. While one of the sisters seems to be keeping her head on straight, as it were, the other appears to be sinking further and further into barbarism and insanity.
