In Fort Chicken, Illinois, a batch of poorly-prepared chicken nuggets containing a mutant virus arrives at Fort Chicken Elementary with fourth-grade student Shelly consuming one of the tainted black-dotted chicken nuggets. At that time, an aspiring Horror story writer named Clint Hadson substitutes at Fort Chicken Elementary, where he is reunited with his former high school crush Lucy McCormick, whom he learned is dating the physical education teacher Wade Johnson. During Clint's class, a boy named Patriot is attacked by a blister-ridden and increasingly feral Shelly after he inadvertently pulls a pigtail out of her scalp, with Clint being scratched by her before she runs. After Patriot is taken to the nurse's office, Patriot's friend Dink confronts Shelly while she attempts to dig her way out of the school. Shelly ends up infecting Dink, who spreads it throughout the playground by scratching the majority of the children before they proceed to kill several staff members including Mr. Peterson, Vice Principal Sims and Sherriff Dave. Later, Clint, Lucy, Wade and the other surviving staff members, consisting of Doug, Tracy Lacey, and Rebekkah Halverson, are forced to flee the faculty lounge when attacked by Patriot. After escaping to the library and joined by uninfected student Calvin, the staff barricades themselves in the music room. Wade notices Clint has been scratched by Shelly and quarantines him, Doug deducing that Clint is only experiencing symptoms of Gastroenteritis as the virus does not affect adults like it does children.