Three friends from the community of Clairton, Pennsylvania, Mike Vronsky, Steven Pushkov, and Nick Chevotarevich, lead a peaceful existence between working in a steel mill and hunting for deer. They prepare to leave for military service in Vietnam, and the shy and clumsy Steve is engaged to Angela, who is secretly pregnant by another man. Mike and Nick both love Linda, who will be moving into Nick’s home after they leave to escape from her abusive and alcoholic father. During Steven and Angela’s wedding, Nick asks for Linda’s hand, and she accepts. As the newly-wed couple drives away, Nick asks Mike to not abandon him in Vietnam under any circumstance. The next day, the social circle, minus Steven, engages in a final deer hunt. After some jokes and discussions, Mike kills a deer with a single shot; it is his custom to fire only once to give the deer a chance of survival. In Vietnam, the friends, along with other soldiers, are captured by the Viet Cong, and are forced to participate in a torturous game of Russian roulette while the jailers place bets. Steven yields to fear and exhaustion and fires his round at the ceiling. As punishment for breaking the rules, Steven is thrown into a cage that is immersed in a river filled with rats and dead bodies. Mike convinces Nick to attempt an escape by inserting three rounds into the revolver’s cylinder; after convincing their tormentors with the increased risk, they kill the captors and escape.
After Steven is freed, the three float along the river’s current on a tree trunk. When they reach a suspension bridge, they are rescued by an American helicopter, but Steven cannot maintain his grip and falls into the water. Mike immediately throws himself in to save Steven, while Nick is detained by the aircraft crew. Steven’s legs are broken in the fall, and Mike carries him until they meet a caravan of soldiers and refugees fleeing to Saigon. Mike rests Steven on the hood of a Jeep. Nick is admitted to a military hospital for physical and psychological trauma, and he ventures to Saigon after he is discharged. In his wandering, he hears gunshots emanating from a gambling den and attempts to leave, reminded of his previous torture experience. However, French businessman Julien Grinda persuades him to come inside and play for him. Mike is present in the den and recognizes Nick, but is unsuccessful in getting his attention. Mike is repatriated and he has difficulty reintegrating into civilian life. He fails to appear at a party organized by his friends. He meets Linda the next morning and learns that Nick has deserted. Mike then visits Angela, who is now the mother of a child, but has slipped into catatonia following the return of Steven, who has been rendered an invalid. Those within Mike’s circle who stayed at home seem to understand nothing of war, and the following days further prove his disorientation; he is unable to shoot a deer during a hunting trip, and in another trip, he sees one hunting partner, Stan, jokingly threatening another partner with a gun. To make Stan understand the gravity of his gesture, Mike violently slips the gun out of Stan’s hand, leaves only one round in the cylinder, points the gun at Stan’s forehead and pulls the trigger on an empty chamber.
Mike visits Steven at a veteran’s facility; both of Steven’s legs have been amputated, and he has lost the use of an arm. Steven has learned of Angela’s infidelity and refuses to come home. He tells Mike that he has been regularly receiving large sums of money from Vietnam. Mike senses that Nick is the source of these payments, and after convincing Steven to return to Angela, he returns to Vietnam in search of Nick. Wandering around Saigon, now in a state of chaos, Mike finds Julien and persuades him to take him to the gambling den. Mike finds himself facing Nick, who has become a professional in the macabre game and fails to recognize Mike. Mike attempts to bring Nick back to reason, but Nick, blinded by his profound suffering, is indifferent. During a game of Russian roulette, Mike evokes memories of their hunting trips. Nick recalls Mike’s “one shot” method and smiles before pulling the trigger and killing himself. Mike and his friends attend Nick’s funeral, and the atmosphere at their local bar is dim and silent. Moved by emotion, the patrons sing “God Bless America” in honor of Nick.