Evanston Hill High School's teacher, Mr. Lorenzo](/actor/peter-giles), oversees the boarding of students onto a bus for an exciting field trip. Among the group is Ever, a shy girl grappling with low self-esteem, who is traveling with her best friend, Tamra. The bus is filled with a diverse bunch of students, including the outcast duo Randall and Steven, who both harbor secret crushes on Tamra and Ever; jock Danny; his loyal best friend Hunt; Danny's girlfriend Jacey; the overweight and bullied Ryan; and the brainy girl Candice.
Suddenly, a terrifying event occurs as blood splatters across the windshield, leading the driver, Wayne, to crash the bus deep into the forest. An urgent radio broadcast soon warns the students of a nearby chemical attack, setting the stage for chaos. Entering the bus is a terrifying figure: a mutated metalhead, later revealed to be a revenge-driven burnout known as [Chip. In a horrific frenzy, Chip attacks Mr. Lorenzo, leaving the students in utter panic. In the scramble, Ever, Tamra, Randall, Steven, Danny, Hunt, and Jacey manage to flee into the surrounding woods, seeking refuge in an abandoned structure. Ryan soon joins their group, while Chip continues his rampage against Candice and others left on the bus.
As they try to regroup in the abandoned building, Ever attempts to help Candice when she risks joining them, but the group decides it’s too dangerous to intervene, leaving Candice to face Chip's wrath. Meanwhile, Wayne, having seemingly transformed like Chip, begins to attack the survivors indoors. The situation escalates when Hunt is captured by what appears to be transformed classmates. Eventually, Ever and her friends find mannequins dressed as themselves, realizing that they are being hunted down one by one. As chaos reigns, Danny is stabbed, starting his transformation into something monstrous, while Wayne makes a sudden return, causing further chaos.
In a heated argument with Tamra, who chooses to side with the jocks, Ever leaves her behind. Ever and Steven venture back to the bus in search of a phone, only to discover that the emergency broadcast was a mere recording. Unfortunately, in a shocking twist, Steven injects Ever with a syringe. As she loses consciousness, she witnesses Randall meet up with Steven, revealing a darker plan that had been set into motion long before. Flashbacks depict how Randall enlisted Steven to create a "Scared Straight!" zombie attack scheme, aimed at wielding power over their bullies and appearing heroic in front of Ever and Tamra. Wayne had volunteered, while Chip concocted a dangerous drug to simulate zombification.
Back in real-time, Randall brings Steven back to the group, conspiring about the students they've taken hostage, including Danny and Hunt. However, Ever gathers enough courage to fight back against Chip using a makeshift weapon. When Tamra confronts Randall about the truth, he inadvertently reveals a mural depicting him and Steven as heroic figures saving the girls from zombified bullies. With this revelation, the students band together to rescue Danny and imprison Steven, taking action against Randall, who inflicts serious injuries on Danny. In a final climactic confrontation, Ever employs a deadly weapon created by Chip to deliver the final blow to Randall, who is now a "zombie" himself.
In the aftermath of the chaotic night, Wayne, Chip, Randall, and Steven find themselves in captivity. The experience fosters a new camaraderie between former bullies and outcasts, with Ever and Tamra mending their friendship. As the surviving students board the bus to leave, they make a surprising discovery: Mr. Lorenzo is still alive!
Weeks later, a PTA worker, Ms. Operative, visits Randall and Steven in prison, revealing that the "Scared Straight" program is making a comeback, and they have been invited to mastermind the initiative.
