The film follows a river journey from South Vietnam into Cambodia undertaken by Captain Willard (played by Martin Sheen), who is on a secret mission to assassinate Colonel Kurtz (played by Marlon Brando), a renegade Special Forces officer accused of murder and presumed insane. The ensemble cast also features Robert Duvall, Frederic Forrest, Albert Hall, Sam Bottoms, Laurence Fishburne, Dennis Hopper, and Harrison Ford.