As the sun gracefully sets behind the hills, Ashley pulls up to the secluded abode of her boyfriend, Ray, a once-celebrated professional hockey player now grappling with the aftermath of being cut from his team. Upon her arrival, an eerie silence envelops the house, prompting Ashley to venture inside. It's her exploration that lays bare the harrowing turmoil within Ray—ominous messages inscribed on walls, a twisted reflection of his spiraling anxiety. Terrified, Ashley flees into the desert but her escape is abruptly halted as she becomes ensnared in a sinister trap, dragged into a decaying shed.
Meanwhile, Gaby arrives at the house, setting off a disturbing series of events that threatens to unravel their reality. The enigmatic Tarkin, Ray's housekeeper, greets her with an unsettling familiarity, his eyes gleaming with an otherworldly intensity. In a chilling discovery, Gaby is confronted with a wall displaying the gruesome visages of her friends alongside her own face adorned with ominous black letters—only to find Ashley’s face crossed out in stark red, sending chills down her spine.
As Gaby gathers with her friends—Freddie, Jade, DJ, Lamont, and Simone—to plan their 10-year high school reunion, tension permeates the air. Their nostalgia is short-lived with the arrival of Gaby’s ex-boyfriend Brad, a Hollywood heartthrob. His new girlfriend Bella further ignites a wildfire of emotions, reviving the painful memories of Gaby's past, marred by abandonment when she was pregnant.
As the night unfolds, the group dives into a game of poker, their laughter intermingled with the haunting reminiscences of their past misdeeds, particularly a cruel prank against John Dougherty, the victim of their youthful cruelty. The scar from the fateful yearbook, which branded him "Most likely to die," lingers painfully in their minds. Soon after, Brad's arrival heightens the ominous atmosphere, breeding unease among the group.
In the shadows, Tarkin's voyeuristic fixation on Bella leads to his downfall when a figure cloaked in a graduation cap, gown, and a menacing papier-mâché mask emerges. This figure enacts a chilling stranglehold on Tarkin, pushing the group further into chaos. As they search for Ray and Ashley, a heavy dread envelops them, only to culminate in the shocking discovery of Ashley's lifeless body, grotesquely wrapped in Christmas lights that chillingly spell her name—a haunting echo of the phrase "Most Likely to Have Her Name Up In Lights."
With panic escalating, Lamont sets off in his car for help, but the vehicle's demise leaves him navigating the perilous terrain alone. Meanwhile, Simone, isolated from the group, falls prey to the masked graduate, marking her as the next victim. Upon returning, the group is met with a gruesome revelation—Simone's body floating in a hot tub, the realization hitting them that they are being methodically hunted down according to their high school yearbook predictions.
Believing Brad to be behind the bloodshed, Bella and DJ venture outside to investigate, but tragedy strikes when the graduate brutally stabs Brad. In the nick of time, Gaby intervenes, but Bella's frantic return results in her untimely demise at the hands of the graduate, her truth dying with her.
As chaos descends, Jade bravely rescues Gaby from the clutches of the masked figure and attempts to shoot him. Yet, in a tragic twist, Gaby inadvertently shoots Jade, leaving her critically injured and bleeding. Meanwhile, Lamont's journey leads him to a comatose DJ, who, despite appearing frail, quickly reveals a darker side. With a merciless intent, DJ turns on Lamont, ending his life with brutal efficiency.
As night gives way to dawn, DJ's facade crumbles, exposing him as the architect of the gruesome acts of vengeance, driven by guilt over John Dougherty’s fate which he facilitated in their youth. He offers Gaby and Freddie a dark proposition: assist him in wiping out the remaining classmates, and they will be spared. Appearing to play along, Gaby cunningly stabs Brad non-fatally before she seizes the gun and fatally shoots DJ, crowning her triumph with the dagger-like retort: > "Who's got the last laugh now, motherfucker?"
In the chilling closing scenes, a mysterious figure clad in a graduation robe stealthily infiltrates DJ's lair, retrieving his mask with an unsettling reverence. This raises chilling implications that John Dougherty may be poised to continue the cycle of vengeance, ensnared in an unending cycle of torment and revenge.
