Motorcycle shop owner and former racer, Frank Stewart, reunites with his buddy, Roger Marsh, at a racetrack following an underwhelming test run by Roger. Their wives, Alice Stewart and Kelly Marsh, step out of Frank's brand new RV, eager for their planned ski trip. After departing from San Antonio, the group finds a serene and secluded spot off the highway to set up camp. As Roger and Frank indulge in some motorcycle racing, a suspicious Kelly takes their dog, Ginger, for a walk. The dog's unease puts Kelly on high alert.
That night, the campsite is alive with chatter and laughter as the couples share a meal. However, Ginger's anxiety lingers. Later, Frank and Roger notice a gathering of robed figures dancing around a bonfire in the distance. Investigating with binoculars, they are horrified to witness an orgy that abruptly turns sinister — a masked leader conducts a brutal ritual, stabbing a young woman in an act of sacrifice. Unbeknownst to them, Alice inadvertently draws attention to their presence, warning the cultists of their watchful eyes.
Upon returning to the RV, the men recount their chilling experience, asserting they witnessed a murder. However, as they attempt to flee, the RV gets stuck in a river. Despite pushing it free, two cult members attack, smashing the back window with logs while Roger struggles to fend them off.
The following morning, they stop at a local police station to report the incident to Sheriff Taylor, who insists on accompanying them back to the ritual site. As they travel, Taylor shares unsettling stories of drug-using hippies ruining the area. Upon arriving, the police discover remnants of the bonfire and bloodstains, but suspiciously no footprints. While Frank stumbles upon a dog hanging from a tree, the sheriff dismisses their claims, suggesting the evidence only belonged to the canine.
Later, as Kelly and Alice discover a violent note left on the RV, the atmosphere grows tenser. After some research into the occult, they seize non-circulating reference books that could help decipher the note's runes. Meanwhile, Sheriff Taylor brushes off their concerns and directs the men to a mechanic.
As the couples try to unwind at an RV park that evening, the unease persists. Ethel and Jack Henderson invite them for drinks, but their excitement turns grim when they find Ginger hung from the RV door the next morning. The couples panic and encounter deadly rattlesnakes trapped inside their RV, leading to a cascade of misfortunes including a crash against a tree.
When they awaken the next day, they find their bikes vandalized, and communication lines cut off. On their journey, they hit another roadblock, but as they attempt to evade their pursuers, their situation becomes dire. The frantic chase leads them to a trap disguised as a school bus fire, full of children in fact safely playing outside. As they try to escape, men, including the mechanic, leap onto their RV.
Fatigued but vigilant, they seek refuge for the night, only to be confronted with a horrifying circle of robed figures surrounding them. As flames engulf the RV and the chanting grows more fervent, the terror reaches its peak while they remain helpless inside their vehicle, trapped in a nightmarish ritual.
