Trick 'r Treat premiered at the Toronto International Film Festival, marking its first public screening.
Principal Pilfer warns the school children about the dangers of breaking Halloween rules, explaining the legend of Sam, the Halloween enforcer.
Lonely Mr. Kreeg is visited by Sam, who punishes him for breaking Halloween traditions by desecrating a pumpkin head and disregarding the holiday customs.
Laurie and her friend Sara go trick-or-treating and encounter various Halloween festivities, later discovering the dark fate of Sara after she breaks a rule about candy tasting.
Rhonda and Wendell go on a Halloween date, where Rhonda's antagonism toward Wendell's costume leads to a violent interaction overseen and punished by Sam.
Burt and Craig prank their friend Steven, who is dressed as a football player, leading to Steven being accidentally killed and later reanimated by Sam.
Steven rises from the dead with a pumpkin for a head and systematically seeks revenge on teammates who betrayed him during the prank gone wrong.
The nature and role of Sam, the Halloween enforcer spirit, is unveiled as protecting Halloween traditions and punishing those that break the sacred rules.
