In the late stage of the Vietnam War, U.S. Captain Willard (Martin Sheen) was ordered to go up the Mekong River to search for Colonel Kotz (Marlon Brando), who had left the U.S. Army and established his own kingdom in Cambodia, and bring him back or kill him. Captain Kotz was once a hero of the U.S. Army in the Vietnam War and had made great achievements. However, suddenly one day, he disappeared. Later, intelligence pointed out that he had established his own kingdom and his own army in Cambodia, specifically opposing the U.S. Army. Willard and several soldiers went up the river all the way. On the way, they witnessed all kinds of atrocities and killings. They witnessed the mental distortion of both U.S. soldiers and locals in the long war and all kinds of abnormal behaviors. Willard was greatly shocked. Willard was finally caught by the locals in Kotz's kingdom in Cambodia and met Kotz. However, Kotz wanted to die and asked Willard to blow this place to the ground...