Private Robert E. Lee Prewitt (Montgomery Clift) is transferred to Schofield Barracks on the island of Oahu. When Captain Dana Holmes (Philip Ober) learns of his reputation as a talented boxer, he pressures Prewitt to join the regimental boxing club that he heads, but the enlisted man stubbornly refuses. 1st Sergeant Milton Warden (Burt Lancaster) suggests that he try to get Prewitt to change his mind by making life as difficult as possible. He gets the other non-commissioned officers to help. Prewitt is supported only by his friend, Private Angelo Maggio (Frank Sinatra).
Behind his commander's back, Warden begins an affair with Holmes' neglected wife Karen (Deborah Kerr). As their relationship develops, she asks him to apply for officer training, so she can divorce Holmes and marry him. When he is finally forced to admit that he doesn't want to be an officer, she sadly ends the affair.
Meanwhile, Maggio antagonizes bigoted Staff Sergeant James R. "Fatso" Judson (Ernest Borgnine). When the undisciplined Maggio goes AWOL, he is sentenced to the stockade, under Judson's charge. Judson takes the opportunity to beat the defiant prisoner repeatedly. Maggio manages to escape and find Prewitt; he tells him of the abuse he endured, then dies. Prewitt finds Judson and kills him in revenge in a knife fight, but suffers a serious wound across the stomach in the process. He then goes into hiding in the apartment of his girl Lorene (Donna Reed), a nightclub "hostess" with whom he has become acquainted. His wound refuses to heal.
When the Japanese attack Pearl Harbor, Prewitt tries to return to camp, but is shot dead by a sentry. At the end, Lorene and Karen meet on a ship leaving for the mainland. Lorene tells Karen that her fiancé was an air force pilot shot down in the attack, but Karen recognizes Prewitt's name.