Laura, Rhonda Gray, receives a letter inviting her to Camp Paradise for a complimentary weekend, a trip that stirs memories of the summer she spent at the same place as a child. She arrives with her new boyfriend, Brad Bartram, and they are drawn into a reunion of old friends: Jennifer, Natalie Main; Tak, Darryl Tong; Nicole, Juliet Martin; and Gerome, Marc Copage, along with Gus, Phillip Bardowell; Sylvia, Donna Correa; Ken, Scott King; Julie, Devon Jenkin; Dean, Kenneth Roper Jr.; and Cheri, Heather Sullivan. Laura’s optimism is tempered by memories of her developmentally disabled brother, Matthew, who died there under mysterious circumstances two years earlier, a detail that will haunt the weekend.
During the party, Sylvia, Donna Correa, and Gus, Phillip Bardowell, are attacked and murdered in an outlying barn by a hulking, monstrous killer—Sylvia is hanged with a rope, while Gus has his arm torn off.
The next morning, Dean, Kenneth Roper Jr., announces that he and Cheri, Heather Sullivan, are leaving, suspicious of the “free weekend” letters. While the remaining guests go for a hike, Ken, Scott King, and Julie, Devon Jenkin, stay at the main house. Ken goes to search for Kane, the Native American groundskeeper, to inquire about Matthew’s death. Meanwhile, Julie finds Gus and Sylvia’s bodies and frantically phones the local sheriff, Elmer Goodes, but the line goes dead, and Julie is killed outside. Tak, Darryl Tong, and Shawn are hunting, and Tak recounts Matthew’s death: two years prior, some of the group teased Matthew for allegedly being gay, and Matthew entered the barn where his body spontaneously combusted before fleeing into the woods, engulfed in flames; his body was never recovered (Matthew, Cleve Hall).
Back at the house, Ken returns and cannot find Julie, but confronts Kane in the barn, who threatens him with a shotgun. Ken flees, but is caught on a bear trap in the woods before the killer slashes his throat. Jennifer and Laura return from hiking, and Laura begins cutting herself in the bathroom before taking a shower. Jennifer is trapped in the ice house by the killer, while Nicole, Jeff, Gerome, and Nancy head to the camp sauna. Outside the sauna, Nancy and Jeff have sex, and the killer impales them with a pole before bludgeoning Nancy with a hammer and scorching Gerome with hot stones.
Kane finds Shawn and Tak in the woods, and pleads with them to leave. He explains that his grandfather, a medicine man, cursed the land after it was taken over by Anglo settlers, and that mysterious deaths have continued there, particularly in the barn. Shawn and Tak are pursued by the killer in the woods and flee back to the main house. Tak frees Jennifer from the ice house, but is murdered by the killer. Jennifer manages to escape toward the barn.
Sheriff Goodes, Noble 'Kid' Chissell, drives toward the camp to investigate the call and finds Dean and Cheri walking along a road, explaining that their car broke down. Goodes drives them back and begins a broader search of the property; upon finding the bodies at the sauna, Goodes is decapitated. Back at the house, Dean searches for the others outside, armed with a rifle, but is confronted by the killer, who summons a bolt of lightning and electrocuts him to death. Cheri is then impaled on mounted deer antlers inside the house.
Outside the barn, Shawn witnesses Kane choking Laura, and he shoots Kane. Laura smiles and confesses that she orchestrated the reunion to punish them for what they did to Matthew. Suddenly, a decayed and burned Matthew appears. Shawn attempts to kill him but is unable to, and Matthew stabs Shawn to death with a pitchfork. Jennifer, the lone survivor, screams in horror as Kane knocks over several gasoline-filled barrels inside the barn and lights a match, blowing up the barn with Kane, Laura, and Matthew inside. Jennifer escapes in the sheriff’s car, and as she drives away, the flames engulfing the barn vanish and it is restored to its original form.
