In the neon-drenched, dial-up era of late 1999, a group of high school friends obsessed with slasher films like Scream and I Know What You Did Last Summer decide to stage the ultimate prank. Led by the charismatic but reckless Jenna Ortega and the horror-obsessed Justice Smith, they plan a fake murder mystery at a secluded lake house, aiming to scare their classmates during a millennium New Year's Eve party. However, their meticulously crafted game takes a terrifying turn when a real, masked killer begins using their script as a blueprint, turning their playful homage into a genuine fight for survival. This darkly comedic thriller blends nostalgic '90s atmosphere with genuine suspense, as the students must decipher whether the threat is one of their own taking the role too far or an outside force with a deadly agenda, all while the clock ticks down to the year 2000.