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

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 dilapidated U-330 on a secret dive, but not all 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 reveals the identity of the spy “Fidelio”. Hannie tracks down the Lebensborn organization.

Schulz kills with his own hand for the second time. Klaus Hoffmann realizes that the Allied invasion has long been underway. A man is waiting in Naples with a murder order.