Harry Mitchell is a successful Los Angeles manufacturer whose wife is running for city council. His life is turned upside down when three blackmailers confront him with a videotape of him with his young mistress and demand $100,000. Fearing that the story will hurt his wife's political campaign if he goes to the police, Harry pretends that he will pay the men, but does not follow through.

A terrified toy salesman is mysteriously attacked, and at the hospital, babbles and clutches the year's most popular Halloween costume, an eerie pumpkin mask. Suddenly, Doctor Daniel Challis finds himself thrust into a terrifying nightmare.