1941: the second year of the Blitzkreig. While occupied Europe writes beneath the Nazi jackboot, Hitler's U-boats dominate the Atlantic trade routes. Kapitanleutnant Konrad Bergman, commander of the UB-44, already responsible for the destruction of the pocket battleship Koenig and all her crew, prowls the enemy convoy routes and finds himself locked in a deadly game of wits with Gestapo informers who suspect his loyalty.

Hunted through the seas by the British, hounded by his enemies ashore, Bergman faces destruction when he and the crew of UB-44 are trapped in a doomed submarine at the bottom of the ocean, with a man who was sworn to kill him.