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).
After attending a medical conference in Beijing and coming frighteningly close to dying in a car crash, Dr Matthew Nolan, played by Armitage (Obsession, Stay Close) arrives home and is immediately arrested at London’s Heathrow Airport. Exhausted and confu