A young man from South West Africa goes to Germany to study nautical engineering and falls in love with a girl whom he later marries. That forces him to stay in Germany and to join the Kriegsmarine, the German Navy, as a submarine officer. During the Second World War he becomes the captain of a successful U-boat, while his wife is killed during an American bombing raid. He finds the new love of his life in occupied Norway. At the end of the war, he is involved in a secret operation, namely to smuggle three tons of Nazi gold to South America in the newest type of U-boat.