In occupied Gdynia, Lieutenant Franz Neumann is drawn into another dangerous espionage game. Engineer Redliński, pursued by the Gestapo, unexpectedly finds Franz, seeking salvation from him. Meanwhile, Bergman recruits the brutal criminal Wulf to track down a traitor in the Kriegsmarine. Franz approaches Bergman's mysterious adjutant, Jorg, to gain information about Bismarck's operational plans.

After the explosion in Greta's apartment, the police start an investigation, and the SS starts to take an interest in her fate. Franz, suspecting treason, looks for the culprits and learns that the caretaker of the tenement house may have been involved in the attack. At the same time, he discovers that the daughter of a Polish engineer is alive and promises to help find her.

Franz, investigating the murder of a janitor, discovers that the killer fired a Russian rifle, suggesting the involvement of a Soviet spy. His investigation leads him to Redliński, who reveals that his daughter Hedwig may know the location of the scientific documentation.