A young man inherits a mansion in a Florida swamp from an uncle he never knew he had. When he, his assistant and the estate's executor arrive at the house, the audience catches sight of someone crawling in the window, though the house is supposed to be unoccupied. As the house staff begins to arrive they sense a strange presence in the house, and when a young woman no one knows runs into the house to escape a knife-wielding psycho, the occupants realize they may be in danger from both outside and inside the house.