When New York writer, Joanna Elliott, flees her abusive husband to the Texas Hill Country, she and her six-year old son, Jason, unwittingly become a killer's prey. Despite Realtor Tommy Joe Greenleaf's warning that Wanda and Ralph Spencer had mysteriously disappeared from the remote farmhouse ten years earlier, Joanna moves in, and makes the sunroom into her office.

Joanna adopts a cat from the local veterinarian, Sam Kelly, who tells her that Sabbath "had belonged to a witch." Unexplained events unfold: Joanna is locked overnight inside the storage shed, footprints appear under the sun room windows, and Jason's dog, Mournful, is found poisoned.