Captain Willard (MARTIN SHEEN) is U.S. Army intelligence officer who's been stuck in a Saigon motel during the Vietnam War, waiting for his next mission. He gets it when he's assigned to travel up the Mekong River into Cambodia and find Colonel Walter E. Kurtz (MARLON BRANDO), a once respected and highly decorated officer who's now gone out of control and apparently out of his mind in creating his own army that reveres him like a god.
Told to terminate Kurtz, Willard gets a ride on a small Navy patrol boat captained by Phillips, the Chief (ALBERT HALL) and crewed by Chef (FREDERIC FORREST), a cook from New Orleans, Clean (LAURENCE FISHBURNE), a 17-year-old from the Bronx, and Lance Johnson (SAM BOTTOMS), a famous surfer from Los Angeles.
As they make their way up the river, they encounter both peril and an odd assortment of characters and situations. That includes Colonel Kilgore (ROBERT DUVALL) and his air mobile fleet of helicopters that make an early morning attack on a Vietnamese coastal village so that some of his men can surf there, a U.S.O. type show featuring Playboy models, and eventually a photojournalist (DENNIS HOPPER) at Kurtz's compound who's completely under the Colonel's hypnotic spell.
With all of the madness they've seen culminating in Kurtz's village, Willard must then decide whether or not to carry out his orders and kill this enigmatic military renegade.