Quiet Diplomacy (S01E03)

In Karlskrona, Commander-in-Chief Börje Lagercrantz devises a covert plan to investigate a submarine for potential nuclear weapons. He assigns his top officer, Captain Hammarberg, to lead this unauthorized mission. Under the veil of night, they close in on the submarine but are soon detected, narrowly escaping with their lives. Meanwhile, in Moscow, Brezhnev learns of the debacle and erupts in fury, demanding that Russian ambassador Aleksandra Kosygina in Stockholm resolve the crisis immediately. Onboard the submarine, Captain Peskov's mental state deteriorates rapidly, leading him to consider destroying the vessel as his only escape.