In the Cambodian capital, Phnom Penh, during May 1973, the Cambodian national army wages a civil war with the communist Khmer Rouge group, a result of the Vietnam War spilling over Cambodia’s borders. Dith Pran, a Cambodian journalist and interpreter for The New York Times, awaits the arrival of reporter Sydney Schanberg at the city’s airport but leaves suddenly. Schanberg takes a cab to his hotel where he meets up with Al Rockoff. Pran meets Schanberg later and tells him that an incident has occurred in a town, Neak Leung; allegedly, an American B-52 has bombed the town. Schanberg and Pran go to Neak Leung where they find that the town has been bombed. Schanberg and Pran are arrested when they try to photograph the execution of two Khmer Rouge operatives. They are eventually released and Schanberg is furious when the international press corps arrives with the U.S. Army. Two years later, in 1975, the Phnom Penh embassies are evacuated in anticipation of the arrival of the Khmer Rouge. Schanberg secures evacuation for Pran, his wife and their four children. However, Pran insists on staying behind to help Schanberg. The Khmer Rouge move into the capital, ostensibly in peace. During a parade through the city, Schanberg meets Rockoff. They are later met by a detachment of the Khmer Rouge, who immediately arrest them. The group is taken through the city to a back alley where prisoners are being held and executed. Pran, unharmed because he is a Cambodian civilian, negotiates to spare the lives of his friends. They do not leave Phnom Penh, but instead retreat to the French embassy. The Khmer Rouge orders all Cambodian citizens in the embassy to be handed over. Fearing an attack from the Khmer Rouge, the ambassador complies. Knowing that Pran will be imprisoned or killed, Rockoff and fellow photographer Jon Swain of The Sunday Times try to forge a British passport for Pran, but the deception fails when the image of Pran on the passport photo fades to nothing, as they lack adequate photographic developer. Pran is turned over to the Khmer Rouge and is forced to live under their totalitarian regime.
Several months after returning to New York City, Schanberg is in the midst of a personal campaign to locate Pran; he writes letters to several charities and is in close contact with Pran’s family in San Francisco. In Cambodia, Pran has become a forced labourer under the Khmer Rouge’s “Year Zero” policy, a return to the agrarian ways of the past. Pran is also forced to attend propagandist classes where many undergo re-education. As intellectuals are made to disappear, Pran feigns simple-mindedness. Eventually, he tries to escape, but is recaptured. Before he is found by members of the Khmer Rouge, he stumbles upon one of the infamous killing fields of the Pol Pot regime, where as many as 2 million Cambodian citizens were murdered. In 1976, Schanberg is awarded a Pulitzer prize for his coverage of the Cambodian conflict. During the ceremony, he tells the audience that half the recognition for the award belongs to Pran. Schanberg is confronted in the restroom by Rockoff, who harshly accuses him of not doing enough to locate Pran and for using his friend to win the award. Although Schanberg initially defends his efforts, he ultimately admits that Pran stayed because of what Schanberg wanted.
Pran is assigned to the leader of a different prison compound, a man named Phat, and charged mostly with tending to Phat’s young son. Pran continues to behave as an uneducated peasant, despite several attempts by Phat to catch him in his deception. Phat begins to trust Pran and asks him to take ward of his son in the event that he is killed. During the Khmer Rouge’s border war with Vietnam, Pran discovers that Phat’s son has American money and a map leading to safety. When Phat tries to stop the younger Khmer Rouge officers from killing several of his comrades, he is ignominiously shot. In the confusion, Pran escapes with four other prisoners and they begin a long trek through the jungle with Phat’s son. The group later splits and three of them head in a different direction; Pran continues following the map with the fourth man. However, Pran’s companion activates a hidden land mine while holding the boy. As Pran pleads with the man to give him the boy, the mine goes off, killing the pair. Pran continues through the jungle alone until he eventually finds a Red Cross camp near the border of Thailand. In the United States, Schanberg receives news that Pran is alive and safe, and he travels to the Red Cross camp and is reunited with Pran. He asks Pran to forgive him; Pran answers, with a smile, “Nothing to forgive, Sydney”, as the two embrace.