In a tense blend of teen drama and time-bending suspense, a notorious serial killer nicknamed Cinderhella roams the halls of Grizzly Lake High, turning prom night into a nightmare for a group of misfit students. Among them are Riley, Ione, Toshiba, Mimi, and Clapton, with Sander quietly nursing an infatuation for Riley. The school’s principal, Verge, sequesters the group in detention until 10 PM on the big night, convinced that one of them is the killer and that fear itself may be the true culprit behind the campus’s chilling atmosphere.
While trapped, the students stumble upon a startling secret: the school’s plush bear mascot is actually a time machine. Their discovery hints at a much larger consequence — the world could end in 1992, allegedly because Ione’s mother Sloane refused to attend prom with Verge. The plot thickens as they uncover a shocking twist: “Ione” is not who she seems. Sloane has swapped bodies with her daughter, and the real Ione exists inside Sloane’s body in 1992. Through this body swap, Sloane even meddles with Riley’s life by taking Clapton, Riley’s crush, which sows tension and fractures friendships in the present-day timeline.
With the bear serving as a portal, the group travels back to 1992, where Ione admits she prefers the past’s vibrant trends and social sway. They learn that Sander is the true killer and that Verge may have contributed to a chain of events that could destroy the world. Despite the danger, Ione agrees to attend the prom with Verge, who promises to spare the world from annihilation. Meanwhile, Riley seizes the chance offered by time travel to intervene in her own family history, striving to keep her father from slipping into alcoholism.
Returning to their original time, the travelers find that the journey has altered some outcomes but not all of the murders. A fragile peace forms as Riley and Clapton become a couple, even as Sander rages with jealousy. In a brutal confrontation, Sander is felled when he is impaled on the bear mascot’s fangs, a grim reminder that the past’s shadows can still reach the present. The students’ relationships shift in the wake of these revelations, and the campus chooses to move forward with new bonds.
The finale sketches a world where some couples persist beyond the chaos: Riley and Clapton begin a romance that survived the truth’s tremors, while Ione, who remains in her mother’s body, marries Verge and often acts as a steadying, if strict, influence over Sloane. Yet the closing image is surreal and unsettling: plants and otherworldly plant-based beings begin to invade, signaling that humanity’s impact on the natural world has drawn the attention of an alien force upset by humans’ treatment of the planet. The film leaves audiences with a blend of closure and cosmic unease, suggesting that even after time-traveling high-school drama is resolved, broader consequences and new threats linger just beyond the horizon.
