During WW II, at the height of Hitler's U-boat war, a group of Allied soldiers made their way home after an exhausting tour of duty; en route, they received orders to assess possible U-boat activity nearby. Captain Rand Sullivan (Scott Caan), and chief of the boat Nathan Travers (William H. Macy), nobly assumed their duty, and lead their weary crew in an initial victory against an enemy boat. Triumph is short-lived, however, as they encounter U-429, led by Jonas Herdt (Til Schweiger). With the Allied boat sunk, Sullivan, Travers, and a few other survivors are taken on board the German ship as POW's. Embarking for a refueling station, Herdt discovers a case of the extremely contagious disease meningitis on board, and as the disease begins to spread they find themselves under deadly attack from an American warship. Realizing that their only hope for survival is to enlist the help of the prisoners, mutiny and infighting is incited, and the American's loyalties are put to the test in a dramatic denouement.