Teenagers David and Lynn, recently orphaned after their father's death, move in with their grandparents, where they uncover a terrifying dark secret about their elderly relatives harboring psychopathic tendencies, including murder. The children witness an ominous woman standing near the grandparents' home, which seems to be connected to a mysterious corpse found nearby. As the story unfolds, David confronts his grandfather, who is revealed to be his father and also a killer, in a shocking climax of violence and revenge.