Mary Oaks, a religious woman, marries a man who proves to be far less than she anticipated. After their first child, a daughter, is born, Mary retreats deeper into her religion and when her husband forces her to make love and she becomes pregnant, she decides this child must be evil. After her husband is killed in an accident, she gives birth to the baby in the house and keeps it in the basement. Five years later, he finds his way out and becomes something of a terror during his nocturnal trips. When he endangers the life of a five-year-old girl, the horror is exposed.