Captain Benjamin Willard, a war-weary American Army officer, receives a covert assignment during the height of the Vietnam War. His mission is to journey up the Nung River into the remote Cambodian jungle to locate and terminate Colonel Walter Kurtz, a decorated but now rogue Green Beret officer who has gone insane and established himself as a demigod among a local tribe. As Willard and the crew of a Navy patrol boat, including the laid-back surf-loving Lieutenant Colonel Bill Kilgore, set off on their top-secret task, they encounter the chaos and absurdity of the war that surrounds them. Their passage through war-torn villages, dealing with the conflict's dangers and moral challenges, serves as a descent into the darkest corners of the human psyche.

The deeper Willard and his crew venture into the jungle, the more surreal and menacing their surroundings become. Encounters with the enemy, the terrain, and fellow soldiers who are losing their grip on reality, chip away at their sanity. Willard becomes increasingly obsessed with his enigmatic target, Kurtz, poring over the dossier provided to him, trying to understand the mind of a man who was once a great military tactician but has now seemingly surrendered to the horrors of the jungle and the war. This intense journey forces Willard to confront not only the realities of the conflict and the dark side of human nature but also the shadows within himself.