A Japanese prisoner of war camp in the jungle on an island in the Malay peninsula at the end of the second world war in 1945. One prisoner is being forced to dig a grave by Japanese soldiers. When he has finished they make him stand by it and shoot him so that he falls back into the grave he has just dug.
Colonel Lambert [André Morell] argues in disgust with the Japanese Captain Sakamura [Marne Maitland] at the way the prisoner has been murdered for attempting to escape. He is permitted to see camp Commander Yamamitsu [Ronald Radd] where, through an interpreter [Wolfe Morris], he complains about the treatment of the prisoners and the conditions. Yamamitsu is angered by Lambert's remarks and warns him about prisoner behaviour and that he will make reprisals against women and children held in another nearby camp if the prisoners do not behave. Lambert leaves to confer with the other officers. It is apparent that the prisoners have destroyed a Japanese radio and that one escapee Keiller is still currently free. Cyril Beattie [Walter Fitzgerald] also thinks Lambert should obey the Japanese as they are making things worse for themselves and those in the women and children's camp by trying to escape.
The camp's chaplain Paul [Michael Goodliffe] is taken by the Japanese to the women's camp to give a burial service. Amongst the prisoners in the women's camp are Keiller's wife Kate [Barbara Shelley] and Beattie's wife Helen [Mary Merrall]. Helen and Father Paul are the only two who understand Latin so he uses this in his burial services to pass messages between the camps.
At the male camp, Lambert inspects the prisoners and encourages one of them to return to the forced labour work the Japanese make the prisoners undertake. The Japanese bring Father Paul back along with a number of mail sacks and a number of boxes. The prisoners want their long overdue mail but Lambert is more interested in what might be in the boxes. Meanwhile, in one of the sick bays, Dutchman Van Elst [Carl Möhner] attempts to tune a home-made radio but hears only static. He narrowly avoids being seen by the guards after he hides the radio and returns to the living quarters. Lambert tells the other officers that Yamamitsu will kill everyone in both camps if Japan loses the war because his previous war crimes mean he will be executed so he has nothing to lose. From what the Allied officers have previously heard on their radio they know the war is now over and Japan has surrendered but they have to keep the news secret from Yamamitsu to avoid a slaughter.
The Japanese get a radio working one night so Van Elst sneaks into the radio room and shorts the circuit out behind the back of the guard. He escapes back to the living quarters while the guard is being reprimanded. The next day the Japanese accuse the prisoners of sabotaging the radio so they take six prisoners as hostages for future punishment and force one of them to burn all of the mail sacks. Just then an American fighter flies over but the pilot Peter Bellamy [Phil Brown] has to bail out before the plane crashes nearby. He is surprised when the Japanese capture him, complaining that the war is over, but the Japanese do not speak English. In their truck they have the recaptured Keiller [Richard Wordsworth]. He tells Bellamy not to tell the Japanese the war is over. Keiller knows he will be executed when they get back to the camp, so as they pass the women's camp he jumps off the truck and runs to see his wife one last time through the barbed wire fence before being shot dead by the guards.
Bellamy is taken to the camp but refuses to give Sakamura and Yamamitsu any information other than his name and rank so they beat him. The Japanese make the prisoners form a parade in order to show them that Keiller has been shot and hostages will be executed if there are any further escape attempts. Beattie again pleads with Lambert to negotiate with Yamamitsu but they fear he will kill all prisoners if he finds out the war is over. Beattie goes to ask to see the Commander, to the concern of the other officers, but Captain Sakamura refuses and knocks him over and Beattie loses heart.
Lambert plans an escape with the others to try and get a message to the Allies via a transmitter on the mainland. They argue over who should go but Lambert insists he should. He asks Father Paul to get a message to Kate Keiller at a burial the next day, so that she can accompany him in the escape. However, when Father Paul gets to the women's camp he discovers that the deceased is Helen Beattie, the only woman who understands Latin, so he is unable to pass the message on.
During the forced labour work the next day, Bellamy and Van Elst manage to escape into the jungle. They overpower a Japanese soldier and steal his jeep but have to hide for the rest of the day to avoid capture. As a punishment for the escapes, the Japanese execute the six hostage prisoners by beheading.
That night Lambert plans an attack with the other officers on the Japanese guards. He has a box of old hand grenades which have been hidden for three years and instructs the men to make any weapons they can.
Bellamy and Van Elst break into the women's camp and Bellamy rescues Kate to help guide them to the mainland, but during their escape Van Elst is shot by the guards. Bellamy and Kate drive to the coast and swim to the mainland although Kate is exhausted and Bellamy has to help her but they reach safety and freedom.
The next day the Japanese bring Van Elst's body back and take another six prisoners for punishment, but Beattie again insists Sakamura takes him to Commander Yamamitsu. In Yamamitsu's office Beattie pulls the pin out of a grenade, killing Sakamura and Yamamitsu and sacrificing himself in the process. In the subsequent confusion, the other prisoners attack the guards with the other grenades and home-made weapons. An intense battle ensues between the prisoners and guards with many casualties on both sides. Then American aircraft fly overhead dropping parachutists and the battle is soon over and the prisoners freed.