English psychology professor Norman Taylor (Peter Wyngarde) is furious when he learns that his devoted wife, Tansy (Janet Blair), practices witchcraft in the hopes that it will advance her husband's career. When he destroys her occult supplies, he unleashes an all-consuming evil. Without Tansy's protection, Norman becomes the target of hostile students and jealous colleagues, and Tansy herself is turned into a potent weapon to destroy her husband.