Near the end of the Korean War, a platoon of U.S. soldiers is captured by communists and brainwashed to be sleeper assassins. Following the war, the platoon is returned home, and Sergeant Raymond Shaw (Laurence Harvey) is celebrated as a hero by the rest of his platoon. However, the platoon commander, Captain Bennett Marco (Frank Sinatra), finds himself plagued by strange nightmares and, together with fellow soldier Allen Melvin (James Edwards), races to uncover a terrible plot.