In Santa Mira, California, a large mask-making company called Silver Shamrock has opened up, selling popular Halloween masks to children across the country.
Dr. Dan Challis, a local doctor, stumbles on a plot to bring about the end of humankind.
He and Ellie (a young woman whose father was recently killed) enter the factory, where they are captured by insane toymaker Conal Cochran, an old Irish man who has stolen a rock from Stonehenge which causes mutations in any person who wears a Silver Shamrock mask.
Challis escapes and, with the help of Ellie, he leaves the control centre in flames while he races to get help and to stop the Silver Shamrock television commercials from airing.
But Cochran will have the final Halloween trick of the night.
Dr. Daniel Challis
Tommy Lee Wallace