Lewis Medlock, Ed Gentry, Bobby Trippe and Drew Ballinger are businessmen from Atlanta. They decide to canoe down the river in North Georgia's remote wilderness before the fictional Cahulawassee River Valley is flooded by the construction of a dam. They are looking forward to seeing the area's unspoiled natural environment and expect the trip to be fun. Lewis is an experienced outdoorsman and takes on the leadership role and although Gentry is also a veteran of several trips he does not have Lewis's leadership skills or confidence. Trippe and Ballinger are first-time wilderness men.
The four travel in two cars, arriving on Friday afternoon at a poor Appalachian residential area close to the river. The people are clearly living in poverty. Lewis tries to find somebody who will drive their cars to a point at Aintry where they can pick them up on Sunday after their canoe trip. Ballinger has a guitar with him and engages a young boy who has a banjo in a friendly musical duel. The boy turns away when Ballinger tries to shake his hand.
The men travel the river in pairs but shortly the canoes are briefly separated when Gentry and Trippe encounter a pair of wild-looking hillbillies coming out of the woods wielding a shotgun. There is a verbal altercation then Trippe is forced to strip at gunpoint and his ear twisted to bring him to his knees. He is ordered to "squeal like a pig" before being raped whilst Ed Gentry is tied to a tree and held at gunpoint by the second man.
Lewis hears the commotion and sneaks up and kills the rapist using an arrow from his bow. The other man escapes swiftly into the woods. Lewis and Drew briefly argue about informing the authorities about what has happened but the other men agree with Lewis who recommends burying the body and continuing as if nothing has happenned. Bobby does not want anyone to know that he was rapes and Lewis reasons that they would never get a fair trial and that a jury would be filled with locals, specifically the friends and relatives of the dead man. Ballinger is troubled by their decision and opposed the course of action the majority has agreed upon. The men continue on their trip but soon reach a stretch of rapides that are extremely dangerous.gentry and Ballinger are in the lead canoe; Drew shakes his head and falls into the water. It is unclear whether this is deliberate.
After his fall into the river, the surviving men collide on the rocks and spill into the river. Lewis breaks his femur and the men all wash up onto the shoreline. Lewis believes that Ballinger was shot in the head causing his tumble into the rapids. Gentry climbs a nearby rock face to try to kill the other mountain man with his bow. He reaches the top and stays overnight. The following morning a mountain man appears on the cliff top with a rifle, looking down into the gorge where Lewis and Trippe are located. He looks similar to the mountain man who ran away from them but it is not made clear that this is the case. Gentry shoots and kills him but accidentally stabs himself with one of his own arrows in the process. Gentry and Trippe weigh the man's body down in the river to ensure it will never be found. When they find Ballinger's body further down the river they weigh him down in the same way.
When they finally reach the small town if Aintry they take Lewis to the hospital. They carefully concoct a story about Ballinger's death being an accident and lie to Sheriff Bullard in order to escape a possible double murder charge. The sheriff tells them one of the locals is missing, never returning from a hunting trip. He clearly does not believe their story but has no evidence that would allow him to arrest them so instead he tells them to never cone back. They readily agree to this and vow to keep their story of death and survival a secret. The final scene shows Gentry waking from a nightmare in which a dead Nan's hand slowly rises from the lake.