The film opens with Mäddy Killian recording footage of her childhood friend Alexis as she prepares for the final days of school and for cheerleading practice. She discusses how important it is to stay in shape and how dangerous cheerleading can be, highlighting how easily advanced stunts can end in severe or deadly injuries. This warning proves tragically true when Alexis is hurled into the air and her teammates fail to catch her in time, leaving her dead.
As school resumes, Mäddy decides to try out for the cheerleading squad and soon earns a spot thanks to her acrobatic skill. During this period, Tracey Beezley begins dating Terry Stankus, the football star who had been involved with Alexis before her death. Mäddy starts to fit in with the other pushers of spirit on the squad—the overly religious and prissy Martha Apple and her shy sister Hanna Popkin, who serves as the team’s mascot. This lively dynamic unsettles Mäddy’s ex-girlfriend Leena, who can’t quite understand why Mäddy has chosen to become so close to the cheerleaders. Unbeknownst to everyone else, Mäddy has joined the squad with a hidden motive: revenge on Terry for reasons that are not yet disclosed.
Mäddy begins laying the groundwork for her retaliation by convincing Tracey Beezley that Terry cheated on her during the summer, and she even manages to lure Tracey into a group gathering of cheerleaders and football players. This rift deeply wounds Leena and infuriates Terry, who escalates the conflict and bans the football players from dating the cheerleaders.
In a fit of anger, Terry punches Tracey, and when the squad tries to flee, he triggers a disaster that costs all the cheerleaders their lives. Horrified, Leena uses Wicca magic and magical stones to revive the dead girls. The next day, the revived team is disoriented and scared, and Martha and Hanna discover they have somehow swapped bodies.
The revived girls can’t recall exactly what happened until Leena explains the events of the previous night. They are also very hungry, prompting them to attack a neighbor to drain his blood. They return to school, where the football players witness something impossible: the cheerleaders, who were presumed dead, are alive again. During the day, the revived squad begins to pick off the football players, driven either by hunger or by anger—Martha, for instance, reacts with fury when she learns that her sister slept with her boyfriend Manny.
Although the group initially tries to stay united, their fragile solidarity begins to unravel as the day’s deaths and Mäddy’s diary entries reveal her true motive for joining the squad. She confronts them with the truth that she joined to exact revenge, but none of the others will listen, especially not Tracey, who has started to fall for Mäddy.
The only person willing to listen is Leena, and Mäddy confesses that she was raped by Terry while filming a memorial for Alexis and that revenge had driven her from the start. The tension mounts as Terry tracks them down, determined to exploit the girls’ magic for his own ends. He believes he can control the power by obtaining the magic stones, but Mäddy and Leena manage to thwart him when Leena’s magic forces the stones out of him.
Mäddy dies once more in the ensuing struggle, only to be revived again by Leena’s grief—an act that mirrors the earlier resurrection. The two share a kiss, momentarily finding comfort in each other, until a gruesome twist reveals Alexis tearing her way out of Terry’s corpse (the person whose grave he had collapsed onto). The film ends with a title card announcing that this is only the first part, and that a sequel is on the way.
