Harry, Ernie Abernathy, his wife Vera, Joleen Mullins, their son Mikey, Ron K. Collie, and daughter Tracy, Kelly Mullis, embark on a wintry camping trip in a remote, snowbound region outside Reno, Nevada. The landscape is quiet and rugged, setting a mood of isolation that hints at danger lurking beyond the trees. Into this peaceful scene arrives Denton Bromley, a destitute but gentle wanderer who travels with a small trailer. The family invites him to stay overnight, and he and the campers share warmth and stories as the night grows colder. Denton, who calls himself Pop, spins a haunting tale about Bernie, his son, who he claims died years earlier after a confrontation with land developers but whom he implies is still alive.
Bernie, played by Blake Gibbons, becomes the dark thread running through Pop’s story. Pop explains how he raised Bernie in a nearby cabin, insisting Bernie once behaved, but the tale takes a grim turn: Bernie is, in fact, alive, chained in Pop’s trailer, and Pop periodically releases him to stalk wealthy outsiders. The unsettling revelation foreshadows the violence yet to come as the forest seems to close in around the family.
That same night, Tracy slips away for a walk along the river, unaware of the danger that has already crept closer. Meanwhile, Bernie slips into the family trailer and murders Harry, Vera, and Mikey in quick, brutal fashion. Tracy returns to find a house of death and the two killers, Pop and Bernie, still nearby. Pop suffers a fatal heart attack while trying to flee with the family’s microwave, and Tracy seizes the opportunity to run, narrowly escaping Bernie’s pursuit through the trees.
As the tragedy unfolds, Bobby, Alex Wexler, and his friend Ron, Joe Balogh, are directing participants of a wilderness training program toward their camp, where Debbie Harris, Jill Foor, later arrives with directions. Another camper, P. J., Ken Hanes, heads toward the same wilderness retreat but is tragically killed when Bernie, wearing P. J.’s clothes, uses the dead man’s Jeep to reach the camp. Tracy’s horrifying realization that the driver is Bernie marks a turn from slow-burning dread to a full-blown chase.
At the wilderness camp, Regis, John Marzilli, presides over the day’s gatherings, while his unconventional partner, Marcie, Ingrid Vold, adds a strange, eerie energy to the camp’s vibe. The group shares campfire stories, and the legend of Bernie becomes a recurring topic among the campers. Debbie, intrigued by the lore, asks Ron to accompany her to Bernie's dilapidated family cabin, a decision that pulls her deeper into the danger. Bernie then strikes with ruthless precision: he kills Marcie in her tent with an axe, amputates Regis’s arm, and shoots him with his own gun, before turning his attention to Chet and Vera in the camp’s makeshift showers, scalding Vera and slashing Chet to death.
As Ron and Debbie start a fire in Bernie's cabin to dry off, the investigation back at Harry and Vera’s camp progresses. Detective Tom Taylor—though the narrative does not establish an actor in the provided cast list—arrives to assess the carnage and soon suspects a crazed methamphetamine addict spellbinding the woods. Back at the wilderness camp, Bobby confronts Bernie, thinking him to be P. J., and is stabbed to death. Sophie, a witness to the violence, flees to the camp but is captured by Bernie.
Tom discovers a grotesque tableau: a swing with the bodies of Bernie’s victims tied to it, campfire songs blaring from a boombox, and Sophie’s struggle on a noose as she’s unable to breathe. His attempt to save her ends in tragedy when Bernie impales him with a spear. Debbie fights back, escapes, and ultimately shoots Bernie with a shotgun, providing a fragile beacon of hope as dawn approaches.
By morning, an ambulance carries Debbie and Tom away from the mountains, Tom barely clinging to life. The night’s horror seems to be ebbing with the arrival of help, but in a final, chilling moment, Bernie’s figure lingers nearby, driving off in one of the police cars and leaving the forest to fester in silence.
