The film opens with a nostalgic trailer for the classic slasher movie, Camp Bloodbath, featuring a group of camp counselors at Camp Blue Finch being hunted down by the masked killer, Billy Murphy (portrayed by Dan B. Norris). We see Max Cartwright, played by Taissa Farmiga, watching the trailer on her phone. Her mother, Amanda, wonderfully depicted by Malin Åkerman, was one of the stars of that film. After Amanda leaves an audition feeling disheartened about being typecast due to her role in Camp Bloodbath, Max tries to lighten the mood. However, an accidental spill of her milkshake onto Amanda's headshot leads to a car accident, setting off a chain of unfortunate events.
Fast forward three years, Max is living with her aunt. One day, her best friend Gertie, portrayed by Alia Shawkat, picks her up along with Chris, played by Alexander Ludwig, to study at a diner. They are soon joined by Duncan, played by Thomas Middleditch, who urges Max to attend a double feature of Camp Bloodbath and its sequel, Camp Bloodbath 2: Cruel Summer. Although Max is initially reluctant as it clashes with the anniversary of her mother’s passing, Duncan’s persistence finally gets her on board as a special guest.
As they arrive for the double feature, the group encounters Vicki, played by Nina Dobrev, Chris's ex. The screening starts, and amidst the excitement, Max finds herself emotional watching her mother on screen once more. Suddenly, chaos erupts when spilled liquor ignites, causing a fire that forces the audience to flee. In a panic, Max leads her friends toward the screen, where they burst through to a blinding light, finding themselves in the woods at the beginning of Camp Bloodbath.
The counselors—particularly the dim-witted Kurt, portrayed by Adam DeVine, and the ditzy Tina—drive by, oblivious to Max and her friends. They wait for what feels like ages until the counselors return. Max tries to keep Nancy, Amanda's character, safe from Kurt, but they soon realize they're trapped in the movie’s timeline. Just as the first grisly murders commence, it becomes clear that they are not merely spectators; they’ve entered a terrifying game of survival.
Duncan meets a brutal fate at the hands of Billy, showcasing that they cannot escape the narrative. The group realizes they need to team up with the tough final girl, Paula, as she is poised to take on Billy. Flashbacks reveal the tragic origins of Billy, igniting the group’s resolve to prevent further victimization. Yet, as attempts to outsmart the movie tropes ensue, a series of traps lead to heartbreak and betrayal, culminating in intense confrontations with the killer.
As the night unfolds, friendships are tested, and they must confront their own vulnerabilities. With the realization that only a final girl can defeat Billy, Max is thrust into a heroic role she never expected. A climactic battle ensues, with madcap antics and desperate sacrifices, ultimately leading to Max embracing her fate. In a devastating moment, she learns that Nancy cannot be the final girl, and it’s up to her to take on the killer and eradicate the evil that has haunted them.
The resolution brings a heart-wrenching sense of closure yet leaves the door ajar for more chaos. Max awakens in a hospital bed beside Chris, only to discover that her nightmare may not quite be over, as they see familiar faces attempting to rekindle old friendships. However, the ominous appearance of Billy through the window hints that their battle is far from finished, plunging them straight into the sequel, setting the stage for another thrilling adventure.
