During World War II, British POW’s are interned by the Japanese at a prison camp off the coast of Malaysia. Known as “Blood Island” for its inhumane treatment of those incarcerated, the camp is ruled by the sadistic commandant Col. Yamamitsu, who has just ordered the execution of a prisoner for trying to escape. When Col. Lambert, the British officer in charge, protests the killing as a violation of the war conventions, Yamamitsu spits on him and promises to slaughter all the prisoners if Japan loses the war. Afterwards, Cyril Beattie, a disgruntled British diplomat, accuses Lambert of inflaming the Japanese by ordering his men to destroy the enemy’s radios and dispatches. Lambert, fearing that the Japanese will retaliate if the war goes badly for them, is trying to prevent all war-related information from reaching the camp. When a shipment of mail arrives for the first time in a year, Lambert worries that two of the crates may contain replacement parts to rebuild the damaged radios. Soon after, Dutch prisoner Piet Van Elst switches on a jerrybuilt radio that he has hidden away and hears a broadcast announcing the surrender of Japan. Knowing that if Yamamitsu learns of the surrender, he will order the massacre of all the POWs at his camp, as well as the women and children held at a neighboring camp, Lambert instructs Dutch to disable the newly rebuilt Japanese radios. As punishment for the sabotage of the radios, Yamamitsu takes six prisoners hostage and declares he will execute them all if he is disobeyed. Some time later, an American plane is spotted on the horizon. When the plane crashes, its pilot, Lt. Peter Bellamy, is captured by some Japanese soldiers who are driving by in their truck. In the back of the truck is Dr. Keiller, a prisoner who has been brutally beaten for trying to escape. When Bellamy tells him that the war is over, Keiller implores him to convey the information only to Lambert. As the truck passes the women’s camp, Keiller, knowing his fate is sealed, jumps out to see his wife Kate, a prisoner at the camp. Kate watches in horror as the Japanese shoot her husband in the back. Upon arriving at the camp, Bellamy is taken to Yamamitsu for interrogation. When Bellamy refuses to divulge any information other than his name and rank, Yamamitsu flogs him unmercifully. Yamamitsu then goes to the camp’s yard where he exhibits Keiller’s body as an example of what will happen to anyone trying to escape. Beattie, who has a wife and son at the women’s camp, snaps at the sight of Keiller’s body and runs to Yamamitsu, trying to tell him that the war has ended. After he is pushed down the stairs and humiliated by the guards, a chastened Beattie returns to the POW hut. Soon after, the badly beaten Bellamy staggers into the hut and points to a map to indicate the location of his carrier ship. Lambert then explains that Keiller was headed for a radio transmitter located in a small Malaysian village off the coast of the prison camp. Only Keiller and his wife Kate knew the way to the village, hence Keiller went to transmit a message to Singapore about the barbarous conditions at the camp. Concerned that a dispatch declaring the end of the war will probably arrive the next day, Lambert decides to make his way to the village and radio Bellamy’s carrier for help. Lambert asks Father Paul Anjou, who is allowed to go to the women’s camp to preside over funerals, to get a message to Kate instructing her to meet him at the water tower the next evening. The priest codes messages into Latin and then recites them at the funerals where Beattie’s wife Helen, who also knows Latin, hears them and passes them along. The next day, the priest is dismayed when he learns that the funeral at which he has been summoned to speak is for Helen, the only person at the camp who understands Latin. As the men toil to build an airstrip for their captors, Bellamy decides to defy Lambert and try to reach the transmitter himself. After Bellamy escapes, Dutch runs after him and they hijack a truck driven by a Japanese soldier. Yamamitsu then orders the beheading of the six hostages as retribution for the escape. Afterward, Lambert assembles the men in his hut and explains that they must prepare to overthrow Yamamitsu. Lambert distributes a crate of corroded hand grenades and tells the men to start manufacturing makeshift weapons. When Beattie asks to join the fight, Lambert hands him a grenade. That night, when Kate fails to appear at the water tower, Bellamy sneaks into camp and finds her. As they are about to escape, the alarm sounds. Dutch is killed while trying to hold off the Japanese, thus allowing Bellamy and Kate to flee in the truck. At the shore, Bellamy asks the exhausted Kate to guide him to the transmitter and helps her swim across the channel. The next morning, as six more hostages are chosen, Beattie asks to speak to Yamamitsu. Once inside the commandant’s office, Beattie pulls the pin on his grenade, thus killing himself and Yamamitsu. The explosion sets off an insurrection by the prisoners, who hurl their grenades at the watch towers. Tom Shields, one of the prisoners, scales one of the towers, seizes the guard’s rifle and begins firing at the Japanese below. Unaware that the gunshots are friendly fire, Lambert lobs his grenade at the tower, killing Shields. Just then, U.S. planes appear overhead and American soldiers parachute into camp to rescue the POWs.