In Blanca Carne, California, the seventeen year-old student Mackenzie Carpenter is celebrating her graduation in high-school with her boyfriend Fisher Kent and her classmates. Mackenzie receives messages about her close friends while they are murdered by Horny The Clown, the symbol of the Hella-Burger fasts food. On the eve of her eighteenth birthday and after the death of a couple of friends, Mackenzie realizes that all of them are connected to a dark event in the past of her mother Marcia Carpenter. Further, she will be in danger on the day of her birthday.