After a peaceful sailboat ride four young people including rich kid Bill Joe Fred and Jane knock on the door of a secluded villa after their dune buggy runs out of gas. Earlier in the day Bill had given the lovely Jane a pearl necklace with a supposedly paranormal history and this later opens up a can of worms. They are invited to spend the night at the mansion owned by Lord Alexander and Lady Alexander who happen to be hosting a strange ceremony that night attended by a group of eccentrics in black robes. During the evening Jane exits her sleep chamber seemingly in some kind of trance and is lured to a sacrificial alter where the robed houseguests are hovering over her. As a knife is about to be plunged into the young lady her three friends come to the rescue but they are also witness to a chaotic mass murder catastrophe in which they flee with feelings of guilt and uncertainty.