Loosely based on actual events during World War II, the film depicts real-life German Captain Bernhard Rogge commanding the navy raider ''German auxiliary cruiser Atlantis'', which from May 1940 to November 1941 sank 22 Allies of World War Ⅱ merchant ships. The story alternates between scenes at the Admiralty and scenes at sea, particularly showing Captain Rogge's humanity and chivalrous conduct of his military engagements. Rogge was one of the few German flag rank officers who was not arrested by the Allies after the war, due to his conduct as a military officer. After eighteen months of successful raids, ''Atlantis'' is sunk on 22 November 1941 by the British cruiser ''HMS Devonshire (39)''.