Irish merchant seaman Murphy is the sole survivor of a World War II German U-boat attack in tropical waters. Picked up by a French oil engineer, he is taken to a native village hospital. Upon recovering, he learns about a downed seaplane, which he repairs and learns to fly. His plan: a personal vengeance on the submarine by destroying it with homemade Molotov cocktails. Murphy is drawn into a relentless struggle against the German boat; it is his private war.