Dr. Daniel Challis and Ellie Grimbridge 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, wants to return Halloween to its darker roots using his masks — and his unspeakable scheme would unleash death and destruction across the country.

A group of kids discover one of the drums containing a rotting corpse and release the 2-4-5 Trioxin gas into the air, causing the dead to once again rise from the grave and seek out brains.