Based on true events, "The Bay of Spies" follows Franz Neumann, a young Nazi Abwehr officer, who discovers that his real father was Polish. Using this information to his advantage Franz becomes a spy for the Allies with the code name Got’ His task is to obtain information about the activities of the German Navy, the Kriegsmarine and report back to the allies. Using his charm and charisma, Franz manipulates the men he gets close to, makes women fall in love with him, and snakes his way into the German elite.

The love between Mateusz Krol, a Kashubian boy, and Marita von Krauss, a Prussian aristocrat in whose family home he is taken in when his mother dies, grows and matures thorough the years, while Kashubia, the northern Polish region where they live, suffers the consequences of the tragedies that will ravage Europe from the beginning of the 20th century until the end of the World War II.