Tom [David Fields] and his fiancée Jeannie [Dawn Laurrie], along with younger sister Karen [Connie Snyder] and her boyfriend Chris [David Fields]—as well as their friends Ron [Jim Cagle] and Lissa [Eve Montgomery]—are on a winter snomobiling vacation in rural Wisconsin to celebrate Chris's birthday. At a local tavern, Lissa is harassed by a drunken racist man who calls her derogatory African American slurs. A kindly waitress, Bessie [Bekki Vallin], apologizes for the patron's behavior, and recommends the group venture to remote trails along Black Friar Lake as part of their snowmobiling excursion.
Along the lake, Tom crashes into a tree and severely injures himself. Chris, a medical student, finds Tom is in shock, and that he needs shelter from the cold. The group find the rustic, abandoned Camp Saint Dominic, a religious summer camp, situated in the woods near the lake, and decide to stay the night. As Tom's condition worsens, Ron departs on snowmobile at nightfall to seek help. Shortly after Ron departs, Tom regains consciousness, but remains weak.
Karen finds a number of mementos from the camp's past, including photographs as well as a makeshift ouija board. Karen, Chris, Lissa, and Jeannie begin to play with the board, though Jeannie is initially reluctant. The pointer on the board begins to spin rapidly, during which Tom goes into convulsions and becomes possessed by a demonic entity. Meanwhile, Ron crashes his snowmobile into a fence and is killed. While Karen and Chris have sex, Lissa explores the lodge, and finds newspaper clippings about a Satanic cult having taken over Camp Saint Dominic. Lissa becomes frightened, and is cornered in a pantry closet by a supernatural entity, where an industrial fan decapitates her.
Chris goes to look for Lissa, but senses he is being watched. He flees outside, where he is impaled through the eye by a falling icicle. Tom insults Karen, suggesting Chris went to find Lissa to cheat on her. Jeannie notices Tom is acting uncharacteristic from his normal self. At Tom's request, Jeannie removes a bandages from his hand and head, and finds his wounds that were there shortly before have miraculously healed. Tom seduces Jeannie, and the two have passionate sex. Meanwhile, Karen is hanged in a volleyball net while exploring the camp gymnasium.
In the morning, Jeannie finds her friend's corpses, and realizes Tom is missing. She consults the ouija board for answers, and it tells her Tom is her enemy, and to leave. As she flees, Jeannie witnesses a cloaked Tom ceremonially knelt beneath photographs of the camp's past visitors. She flees on a snowmobile, but is pursued by Tom, who boards Ron's crashed snowmobile. A protracted chase ensues before Tom crashes into a snowplow, which runs over his body, crushing him and causing his snowmobile to explode. Tom, caught in the inferno, is burned alive. Jeannie flees the scene as a sheriff [Jim Gresch] arrives.
In voiceover narration from thirty years in the future, Jeannie, recalling the events, explains that she revisited Black Friar Lake and found the camp was merely a set of ruins—it had burned down decades prior. She expresses regret over agreeing to partake in the ouija board, but that the curiosity to do so was in her nature.
