Lewis Medlock, Ed Gentry, Bobby Trippe, and Drew Ballinger are businessmen from Atlanta who embark on an adventurous canoe trip down the Cahulawassee River in the untouched wilderness of northern Georgia before it is flooded due to dam construction. Leading the expedition is the experienced and confident Lewis, while Ed possesses outdoor skills but lacks Lewis’ bravado. On the other hand, Bobby and Drew are greenhorns. During their drive to the launch site, they show disrespect toward the locals, which leads to a hostile atmosphere. At a nearby gas station, Drew challenges a young banjo player to a musical duel, which brings some locals joy and prompts them to dance, although the boy refuses to shake Drew's hand afterward.
As the friends paddle in pairs, their canoes drift apart, leading Ed and Bobby to encounter two intimidating mountain men. One of them, armed and with a menacing smile, forces Bobby to strip, and in a shocking moment of violence, he brutally assaults him, ordering Bobby to "squeal like a pig." Meanwhile, Ed finds himself tied up and threatened. Quick-thinking Lewis saves the day with his bow and arrow, taking down the rapist and allowing Ed to seize the shotgun from the other man, who runs away. After a fraught discussion about what to do next, the group decides to bury the body and leave the incident behind.
Their journey continues, but soon they reach treacherous rapids. As Drew and Ed navigate ahead, Drew falls overboard, prompting a catastrophic capsize that injures Lewis and scatters the others across the jagged rocks. Lewis, convinced Drew was shot, urges Ed to scale the gorge and set an ambush for the lurking mountain man. Under the cloak of darkness, Ed waits until dawn, and when he spots a figure above, panic takes over. He accidentally pulls the trigger and kills the man but falls onto one of his arrows in the process. Doubt creeps in as he inspects the corpse, initially fearing he has made a grave mistake, only to realize the man was wearing dentures. Determined to conceal their actions, Ed and Bobby sink the body in the river, as well as Drew's lifeless form when they discover him downstream.
Upon reaching the small town of Aintry, Ed and Bobby rush Lewis to the hospital. The trio fabricates a story for Sheriff Bullard regarding Drew’s death, but their lie is almost exposed when Ed mistakenly thinks Bobby confesses to the truth. In the hospital, while under the watchful eye of a police officer, Ed expresses concern about their deceit to Lewis, who calmly dismisses the need for change, citing memory loss due to his injury. Sheriff Bullard, suspicious due to a missing hunter in the area, confronts the men but ultimately does not have enough evidence to detain them, cautioning them never to repeat such a reckless adventure. The three men make a pact to carry the burden of their secrets indefinitely.
Afterward, Ed returns home to his family, yet peace eludes him. Sometime later, a chilling symbol of his trauma emerges as a decomposed hand rises from the depths of the lake, haunting him with the torment of their harrowing experience.
