Former Marine John “Chickie” Donohue is a slacking merchant seaman who lives with his family in Inwood, New York City, and likes to hang out at a bar operated by a somewhat cynical old man dubbed “The Colonel”. Chickie's sister Christine is strongly opposed to the Vietnam War in contrast to Chickie and their father, who also formerly served. Upon learning that an old friend, Johnny, is killed in action, Chickie and friends attend his funeral and are informed that another close friend, Tommy Minogue, whom Chickie persuaded to join the draft, has gone missing in action. After the funeral, Chickie and his friend Red find Christine in an anti-war demonstration and get into a brief physical altercation with some protestors. Back at the bar, Chickie and Red talk about how they could lift their serving friends' spirits. Chickie has an idea to go to South Vietnam himself and deliver his friends some beers. The next day, Chickie appears to backtrack on this, but as Tommy‘s mother suggests Chickie take to her son a set of rosary beads if he finds him, he sets out on the trip against Christine's warnings.

Chickie, a merchant mariner, signs on to a ship sailing to Saigon with a duffle bag full of Pabst Blue Ribbon cans in search of military policeman Tommy Collins. He finds Collins, who is ecstatic to see him. That night, Collins' superior officer comes in and chastises Chickie for delivering the beers, then suspects him to be a CIA agent. Chickie and Collins' friends map out a plan for reaching Chickie's other friends. With guidance from a local named Hieu, Chickie stops at the Caravelle Hotel, where he finds American and British reporters opposed to the war. Using his CIA guise, he hitches a ride on a military caravan to Bien Hoa Air Base and is flown to Danang Air Base and then on to LZ Jane, where he searches for Rick Duggan, who is serving in the 1st Cavalry Division. Duggan’s sergeant radios him to report to the command post, forcing Duggan to run in plain sight under enemy fire. When Chickie surprises him, Duggan reacts angrily but allows Chickie to join him and his squad on the battlefield as they fire upon the Viet Cong from trenches. When night falls, Chickie again passes around beers. Duggan also tells Chickie that one of their friends, Reynolds, was killed. After parting ways with Duggan in the morning, Chickie is put on a chopper with two CIA agents who brutally interrogate and throw out a prisoner.

Landing at Kontum Airfield, Chickie requests a ride to Saigon, and one officer explains that he may leave his post to escort Chickie to Pleiku Air Base. When Chickie looks outside, he sees the officer driving a prison caravan. Realizing the agents are after him, he runs into the jungle, hiding until the agents give up the chase. Chickie walks alone and passes by a busted jeep and a child playing in the streets. At the sight of Chickie, the child cries in fear before its mother runs away with the child away. Later that night, after nearly being trampled by elephants running from napalm, Chickie is found by another old friend, Kevin “Looney” McLoone. Despite their orders to move in the opposite direction of where Chickie is headed, Chickie persuades McLoone and his men to drive him to Pleiku. McLoone puts Chickie on a chopper, and Chickie throws him his beer as the helicopter accends.

Back in Saigon, Chickie learns that his ship has left early due to warnings of an impending attack and is on the way to the Philippines.