The film begins with the familiar image of the roaring MGM lion logo filling the screen.
The scene abruptly cuts to a blindingly dusty airport in South Vietnam. U.S. Army volunteer Chris Taylor (played by Alex Hayes) arrives in 1967. The first scenes Taylor witnesses are the somber, ongoing operations of war: covered bodies of soldiers being prepared for transport back to the USA, and the hollow, lifeless stare of a living, experienced soldier who passes by.
The action immediately transitions to the oppressive density of the Vietnamese jungle. Taylor and other new replacements are assigned to an infantry platoon of the 25th Infantry Division operating near the Cambodian border. The platoon is led by the young and noticeably nervous Lieutenant Wolfe, who heavily relies on his two veteran non-commissioned officers: the ruthlessly cynical Staff Sergeant Barnes (played by Tom Berenger), and the morally grounded Sergeant Elias (played by Willem Dafoe).
As the platoon rests in a temporary camp, we are introduced to the remaining core members, a diverse group sharing the weight of their immediate situation: Sgt. O'Neill (John C. McGinley), King (Keith David), Rhah (Francesco Quinn), Junior (Reggie Johnson), Big Harold (Leory Johnson), Tex (Mark Moses), Manny (Keith P. Walker), Warren (Tony Todd), Ace (J. Adam Glover), Sal (Richard Edson), and Lerner (Johnny Depp).
Taylor, the new arrival, settles in, and his internal struggle is heard in a voiceover monologue, the camera focusing on the visible exhaustion and weariness on his face. This raw display of fear and fatigue immediately signals to the audience that this is not a typical film for Alex Hayes.
The audience hear the Taylor's inner monologue: "Somebody once wrote: "Hell is the impossibility of reason". That's what this place feels like - hell. I hate it already and it's only been a week. Some goddamn week, Grandma. The hardest thing I've ever done is go on point. Three times this week. I don't know what I'm doing. A gook could be three feet in front of me and I wouldn't know it. I'm so tired. We get up at 5am, hump all day, camp around four or five, dig a foxhole, eat, then put out an all-night ambush or a three-man listening post. It's scary 'cos nobody tells me how to do anything, 'cos I'm new. Nobody cares about new guys. They don't even wanna know your name. A new guy's life isn't worth as much 'cos he hasn't put his time in yet. They say if you're gonna get killed in the Nam, it's better to get it in the first few weeks. The logic being you don't suffer that much. If you're lucky, you stay in the perimeter at night. Then you pull a three-hour guard shift. Maybe you sleep three, four hours a night... But you don't really sleep. I don't think I can keep this up for a year, Grandma. I think I've made a big mistake coming here."
Taylor soon participates in a tense night ambush of a North Vietnamese Army force. Taylor is wounded during the firefight, while another new replacement, Gardner, is killed due to his inexperience. After a brief return to the base's aid station, Taylor bonds with Elias and his circle of marijuana users—the "heads"—a clique distinct from Barnes and his hard-edged followers. It is during this time we learn Taylor gave up college and volunteered to fight in Vietnam because of youthful ideals. This revelation causes Vietnam veterans watching the film to reflect on their own naive friends who did the same, and perhaps their own past selves.
During the next patrol, two soldiers are killed by a booby trap, and the black soldier Manny is abducted by unseen assailants, who later stage his corpse. The platoon finds Manny's body and, enraged, descends upon a nearby village, finding a supply cache hidden there. It is here, in the village, that the terrified Taylor, his conscience and fear warring, confronts a blind man and, though he spares his life, the man is immediately killed by the psychotic soldier Bunny (played by Kevin Dillon). The audience sees Taylor on the edge, struggling to hold onto his humanity in the face of war's reality. Barnes aggressively interrogates the village chief and murders his wife in front of the horrified villagers. When he threatens to murder the chief's daughter, Elias intervenes and assaults Barnes. Lieutenant Wolfe separates the two, orders the destruction of the supplies, and the village razed, but feigns ignorance when Elias accuses him of failing to stop Barnes. Taylor, witnessing the atrocity, prevents two girls from being gang-raped by some of Barnes's men.
Company commander Captain Harris soon threatens to court-martial anyone found to have illegally killed civilians, and orders Barnes and Elias to put aside their increasingly dangerous differences. Following this, the conflicts between the two groups—those supporting Elias and those supporting Barnes—deepen. The men on Elias's side begin to feel profound confusion about the nature of the war and their role in it, questioning who is good and who is bad, and whether they are the good guys at all. Taylor becomes close with Elias during this tumultuous time.
On their next patrol, the platoon is ambushed and pinned down. In the chaos, Lieutenant Wolfe directs artillery fire onto his own unit before Barnes calls it off. Barnes orders Elias, Taylor, Rhah, and Crawford to intercept flanking enemy troops, pulls the rest of the platoon back, and then goes out to retrieve Elias. When Elias is briefly separated from the others, Barnes takes the opportunity and shoots him. During the subsequent helicopter extraction, Barnes tells Taylor that Elias is dead, but as they fly out, they see the mortally wounded Elias stagger from the jungle, pursued by NVA soldiers, who kill him in a hail of gunfire. It is the most emotional scene, witnessing the death of a good man.
Taylor attempts to talk the heads into fragging Barnes in retaliation, not realizing Barnes has overheard them. He enters the abandoned bunker they use for gathering, taunts them, and fights off an attack by Barnes, cutting Taylor's face with a push dagger.
The severely weakened platoon is sent back out to a defensive position. A major NVA night assault occurs, tearing through the unit. Much of the platoon is killed, including Wolfe and most of Barnes's hard-line followers. An NVA sapper destroys the battalion headquarters in a suicide attack, forcing Captain Harris to call an air strike on their rapidly shrinking perimeter. The entire scene is pure, unrelenting chaos, allowing the audience to viscerally experience the terror.
In the height of the confusion, Taylor encounters a seriously wounded Barnes, and as they grapple, both are knocked unconscious by the explosion of the air strike.
When Taylor regains consciousness after sunrise, he finds the grievously wounded Barnes. Barnes, in a final act of dominance, dares Taylor to kill him, and Taylor shoots him dead in cold blood. There is no emotion in Taylor's eyes—no joy, no sadness—only the final, numb realization of the war's effect on him. One of the soldiers stabs himself in the leg, reminding Taylor that men wounded twice are returned home. As a helicopter carries the two men away, Taylor waves goodbye to Rhah. Command of the remains of the platoon is given to the cowardly Sgt. O'Neill. An overwhelmed Taylor sobs as he flies away from the battlefield, narrating how the war has changed him forever.
The film ends with Taylor's inner monologue:
"I think now, looking back, we did not fight the enemy, we fought ourselves, and the enemy... was in us. The war is over for me now, but it will always be there, for the rest of my days, as I'm sure Elias will be, fighting with Barnes for what Rhah called possession of my soul. There are times since... I've felt like the child born of those two fathers. But be that as it may, those of us who did make it... have an obligation to build again, to teach to others what we know, and to try with what's left of our lives... to find a goodness, and meaning, to this life."
The last frame displays: 'Dedicated to the men who fought and died in Vietnam war'
The film concludes with an immense silence settling over the audience. It is not a glorifying war film; rather, it is a brutal and thrilling account that lays bare the war's effects on the soldiers' morality and evokes profound emotion.
Alex Hayes, who played Taylor, felt emotional seeing the film even though he had already seen it. He looked out at the silenced theater, knowing exactly what they experienced. Suddenly, one of the veterans in the crowd started clapping, before the applause spread to the whole theater.
Alex felt Mia's hand on his, and he gave her a genuine smile that replaced his weariness.
The theater lights rose. Oliver Stone, the director, was immediately there, his face full of pride.
"You did it, Oliver," Alex congratulated Oliver.
"No, we all did it, Alex," Oliver said, gripping his shoulder.
Then, a wave of cheers broke over them as the other cast members and producers joined in.
In that moment—feeling the audience's reaction, the support of his peers—Alex Hayes knew, with certainty, he had succeeded again, by believing in the film.