Dr. Ralph Hayes, a professor of parapsychology, takes a research team into the Louisiana swamp where eight women have been murdered, drained of their blood, and marked with satanic symbols. The investigating party includes: Maggie, the professor's secretary; Tasha, a student whose grandmother was a witch; Victor Gordon, a magazine writer; and several students of witchcraft. Tasha's extra-sensory powers are detected by Luther, a warlock who has committed the murders in accordance with a pact made with the Devil. To gain control of Tasha, he calls forth Jessie, a 200-year-old witch who will help only if she receives enough blood to restore her youth. When Tasha aids Luther in luring two students to their death, Dr. Hayes and Victor realize the strength of Luther's hold over Tasha. During a ceremony to make Tasha a witch, Dr. Hayes and Maggie are killed trying to divert Luther's attention, while Victor substitutes pig's blood for the human blood. All in the coven are destroyed but Luther, who chases Victor and Tasha into the swamp. In the struggle, Luther falls into quicksand, and Tasha, proclaiming Satan to be her master, pushes Victor into the quicksand.