Dr. Daniel Challis (Tom Atkins) and Ellie Grimbridge (Stacey Nelkin) stumble onto a gruesome murder scheme when Ellie's novelty-salesman father, Harry, is killed while in possession of a strange mask made by the Silver Shamrock mask company. The company's owner, Conal Cochran (Dan O'Herlihy), wants to return Halloween to its darker roots using his masks -- and his unspeakable scheme would unleash death and destruction across the country.