Season 3 follows the fortunes of a young U-boat crew as they engage in the Battle of the Atlantic, are hunted down by an obsessed Royal Navy Commander (Ray Stevenson) and are sent on a dangerous mission to the Southern Hemisphere. Together they form strong personal alliances under the command of Robert Ehrenberg (Franz Dinda).

1941年，德军准备入侵苏联，德国男青年Wilhelm和他的弟弟Friedhelm响应希特勒的号召应征入伍，即将奔赴前线。女青年Charlotte立志为国家服务，成了一名女护士，也将前往战场救助伤员。女青年Greta美丽活泼，歌声动人，她希望有朝一日成为一名女歌星。她的情人是一个犹太人Viktor，他是一名裁缝的儿子。五人是最好的朋友，他们在启程的前夜载歌载舞，喝酒庆祝，约定圣诞节再相聚。　　分离之前，他们都是意气风发的年轻人；分离之后，他们的命运便和这场战争紧紧联系在一起。对于这一辈的德国人来说，这是他们的父辈、他们的母辈对于这场战争的记忆。

Vienna, 1920. The Austro-Hungarian Empire has collapsed. Peter Perg returns home from the Great War, after seven years as a Russian POW. Vienna is experiencing the multiplicity of political, social and artistic freedom, but also the rise of anti-democratic movements, insecurity and unemployment. Peter, a former police inspector, feels like a stranger in the new Austrian Republic. While wanting to leave town, Peter is confronted with the murder of one of his former comrades. He decides to stay and instead bring the killer to justice. His ally is Dr. Theresa Körner, a determined and cool-headed forensic doctor. The two are linked not only by this case, but also by a deeper, shared history. As their investigation progresses, they realise that they are not just up against a systematic killer, who tortures his victims, but also face disapproval and intrigue from within the police force. Though determined to solve the crime, Peter, harbouring his own secrets, increasingly becomes tormented by existential questions What is truth What is heroism in the time of war And all the while he fails to see the mounting danger before him.