France, 1942: In the submarine port of La Rochelle, the 40-man crew of the U-612 prepares for its maiden voyage. The young men face an unknown mission in the increasingly merciless Battle of the Atlantic during the Second World War. As the new Kaleun, the less experienced Klaus Hoffmann (Rick Okon) is in command - to the annoyance of the older first watch officer Karl Tennstedt (August Wittgenstein). Over the course of the mission, the skills, loyalty and camaraderie of the entire team are put to the test. At the same time, Simone Strasser (Vicky Krieps) arrives at the base to work as a translator for Gestapo boss Hagen Forster (Tom Wlaschiha). Simone's brother Frank (Leonard Scheicher) is also stationed in La Rochelle. Shortly after their first reunion, Frank asks his sister for a favor that will change her life forever. Soon Simone is forced to question everything she has previously believed.

December 1942: The experienced submarine commander Johannes von Reinhartz (Clemens Schick) and his crew set sail with U-822 on a secret mission. However, when the captain's loyalty is soon questioned, U-612 under the command of Ulrich Wrangel (Stefan Konarske) gives chase. Klaus Hoffmann (Rick Okon) was able to escape death on the Atlantic. In New York he is taken in by Sam Greenwood (Vincent Kartheiser) and through him gets to know the shady lawyer Berger (Thomas Kretschmann). Can this enable him to return to Germany? In La Rochelle, Simone (Vicky Krieps) continues to be active in the resistance, although Gestapo chief Forster (Tom Wlaschiha) has her in his sights. Together with Margot (Fleur Geffrier) she wants to help a Jewish family escape.

The third season of "Das Boot" follows the fate of an inexperienced submarine crew who are sent on a dangerous mission and find themselves in the sights of an obsessed Royal Navy commander. Under the leadership of Robert Ehrenberg (Franz Dinda), strong personal alliances form within the crew. Ehrenberg himself finds family ties that he thought were lost forever. Meanwhile, in neutral Lisbon, where exiles, spies and criminals meet, Hagen Forster (Tom Wlaschiha) uncovers a deadly plot to steal looted war gold. His investigation also leads him to a man involved in a conspiracy that could change the course of the war for the better: Klaus Hoffmann (Rick Okon).

The events of the fourth season of "Das Boot" begin in the summer of 1943: Klaus Hoffmann is celebrated as a hero in Berlin, but at the same time he is shadowed. His sister Hannie, whose marriage only exists on paper, has found a new job. Meanwhile, the navy suffers heavy losses in the Mediterranean. The film was directed by Dennis Gansel (“The Wave”) and the main actors in the six new episodes include Rick Okon and Rosalie Thomass.