Klaus Hoffmann pursues the German agent Weiss and discovers valuable information. U-949 is under heavy fire from Swinburne's destroyer - until Commander Buchner dares a manoeuvre.

The U-boat crew struggle with recent events and what lies ahead. A revelation in La Rochelle infuriates Forster spelling bad news for Simone.

The U-949 reaches Portugal and unloads the gold. When Ehrenberg returns to Kiel, he finds Greta with her husband again. Klaus Hoffmann and Forster reach their goal through blackmail.

Wrangel catches up with Johannes, leading to a dramatic showdown out in the Atlantic. Hoffmann shows up at Cassandra's place.

Hoffmann struggles to hang on as his chance to escape heads toward US shores. Margot pushes on with her plans.

Keen to impress his superiors, Forster cracks down on Anatole's wayward behaviour. Wrangel finally has his arch rival in sight.

A surprise new arrival takes Greenwood's place, causing a divide. Plus, Carla and Simone grow closer and a resistance fighter arrives at the safe house.

Things look bleak for the crew of U-612, as they desperately try to work out their next move. Simone adjusts to her new position between Carla and Forster.

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.

Forster reveals to Simone that U-612 has gone missing. Meanwhile, the resistance endanger the innocent to further their cause.

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.

The U-949 is in danger during a test drive due to Commander Buchner's orders. Forster comes across a trail in a casino and makes the acquaintance of the German Bettina Gruber.

Spring 1943: L.I. Ehrenberg prepares submarines for use in Kiel. Minors are recruited as crews. Wilhelm Hoffmann attends a reception at the request of his son-in-law.

An inexperienced U-boat crew are plunged into a perilous secret mission, while new translator Simone starts work at the base.

Forster is investigating the village man murder case in Lisbon. In Kiel, the new sailors of the U-949 get into battle. Royal Navy captain Swinburne is travelling to Liverpool for his son's funeral service.

While Swinburne sets sail with a technologically upgraded ship, Ehrenberg makes a serious decision in Kiel. Forster has to create a traitor out of the country.

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

Hoffmann insists on further training despite the crew's desire to head to battle. In La Rochelle, Simone pieces together the previous night's events.

Unity on U-612 has crumbled and Hoffman and Tennstedt's continued conflict could jeopardise the mission. On land, Simone wrestles with a difficult choice.

U-949 meets a Japanese boat to take over heavy cargo - gold. Wilhelm Hoffmann receives an invitation to Lisbon. Forster betrays Klaus Hoffmann under duress what he knows.