A group of war prisoners has spilt blood, sweat and tears to construct a bridge over the river Kwai in Thailand. Just when the bridge is ready, an American bomber arrives and destroys it. Camp commander Tanaka wants to set an example and orders that some of the prisoners must be executed. Just in time major Harada arrives with orders that the healthiest prisoners must be transported to Japan by train and boat. A treacherous journey since the allied forces keep a close eye on railroads and practically own the seas.