Inside a mining shaft, a female miner undresses in front of a male worker. During the uneasy private moment, he notices a heart tattoo on her body, and in a sudden burst of rage he hurls her onto a mining pickaxe, killing her. The brutal opening sets a brutal mood that threads through the town’s history and its present-day decisions.
Valentine Bluffs, a Canadian mining town, is drawn back to the surface of old memories when Mayor Hanniger reinstates the traditional Valentine’s Day dance that had been paused for two decades. The backstory is dark and tragic: twenty years earlier, two supervisors abandoned five miners to attend the dance, forgetting to check methane levels in the tunnels. A catastrophic explosion collapsed the mine, trapping the workers. Harry Warden survived by turning to cannibalism to endure, losing his sanity in the process. The next year, he returned to punish the town: he murdered the two supervisors, removed their hearts, and placed them in Valentine candy boxes with a warning that the town should never hold the dance again or face more killings. Warden was later declared mentally unwell and institutionalized, and the incident faded from memory, allowing the dance to resume. A new generation of residents—Gretchen, Dave, Hollis, Patty, Sylvia, Howard, Mike, John, Tommy, and Harriet—get swept up in the excitement, while Sarah, Axel, and the mayor’s son T.J. find themselves entwined in a tense love triangle.
The mood sharpens when the town receives an anonymous box of Valentine chocolates, each containing a human heart, accompanied by a note threatening murders if the dance goes forward. That very night, Mabel is murdered by a miner-suited killer in a laundromat, her heart removed, and the police chief Jake Newby chooses to report her death as a heart attack to prevent panic. He checks for any record of Harry Warden in the mental institution, only to find nothing conclusive. In response, Hanniger cancels the dance, but the younger residents press ahead with their own party at the mine. A bartender cautions them against this plan, but is killed by the unknown killer while trying to rig a dummy miner to spook the partygoers.
As the revelry unfolds in the shadow of the mine, Dave is brutally slain and his heart appears boiling in a pot of hot dogs being prepared in the kitchen. Soon after, Sylvia is impaled on a showerhead, sending shockwaves through the group. When the authorities are contacted, several partygoers have already decided to explore the tunnels for thrills. TJ and Axel descend into the mine to search for the missing, while Hollis splits off to find Mike and Harriet, who have been impaled by a large drill. Hollis is then killed—shot in the head with a nail gun—and the killer closes in. Howard flees in a panic as the killer arrives; Patty, TJ, Axel, and Sarah attempt to escape with a ladder, but Howard’s corpse, tied to a rope, falls from above.
As the survivors navigate the treacherous tunnels, Axel appears to meet a grim fate, only to reveal himself alive as a devastating twist unfolds. A brutal chase leads to a reveal: Axel is the apparent killer, his actions rooted in a personal history that ties back to the Warden era. A flashback explains that Axel’s father was one of the supervisors killed by Harry Warden, a memory that haunts him. In a desperate moment, TJ strikes Axel with a rock, causing the tunnel to collapse and trapping Axel as Newby and the rescuers close in. They learn that Harry Warden died five years earlier, but the nightmare isn’t over. A rescuer shouts that Axel is still alive, and TJ and Sarah hurry back to the scene. Axel frees himself by amputating his trapped arm, then sprints deeper into the mine, still steering his madness toward a chilling vow: he and Harry Warden will return to murder everyone in town, muttering about Sarah as his “bloody valentine.”
The closing scene lingers on the killer’s deranged laughter as a ballad dedicated to Harry Warden swells over the credits, leaving the audience with a haunting sense that the terror may not be finished.
The film also features the ensemble cast, including Danny Webb as Cafe Owner, Tom Greaves as Him, Alex Hughes as Crazy Jimmy, and Gemma Atkinson as Her.
