The story is about a girl, Rachel Bryant (Linda Blair), who lives with her wealthy family in a nice house in the hills of Northern California. After her mother's sister, brother-in-law, and housekeeper die in a horrible car crash, the couple's daughter, Julia (Lee Purcell) comes to live with them. Julia seems a little shy if anything, but as time goes on, she begins to put an alluring spell over everyone she meets, pulling all of Rachel's family and friends away from her. After finding some odd things that belong to Julia (including a human tooth and burnt hair from Rachel's dog Trickle (for the movie the dog was changed to a horse due to Blair's love of horses and the name of the horse was Sundance instead of Trickle), Rachel begins to suspect that her cousin may be a practitioner of witchcraft, and she's hell-bent on turning Rachel's life upside down. Her open disbelieved suspicions caused her to become an outcast in front of her family.