August 1943: Franz Buchner is in action with the U-949. An informer on board divides his crew. The Hoffmann family gathers in Berlin to attend the premiere of a film about Klaus.

Robert Ehrenberg supports the resistance within the Navy and gives Klaus Hoffmann a clue. Bobby Schulz is on his trail. U-949 comes under fire in the Strait of Gibraltar.

Commander Buchner reaches the coast of Naples. Klaus Hoffmann is also on his way there. His sister Hannie meets twelve-year-old Hertha.

Klaus Hoffmann commands the ailing U-330 on a secret dive, but not all the men trust him. Hannie wants to take Hertha in. Staff officer Heinrich Gluck has to make a decision.

After a risky maneuver, the U-330 appears next to a US Navy ship. SS man Koch uncovers the identity of the spy "Fidelio". Hannie gets on the trail of the Lebensborn organization.

Schulzhugs with his own hand for the second time. Klaus Hoffmann has to realize that the Allied invasion is already underway. In Naples, a man with a cuddle mission is waiting.