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 story begins in the summer of 1997, just before the arrival of the famous 12-meter flood wave flooding Wroclaw. - The residents of the "Home under Two Eagles" are grandma Zofia Szablewska, a woman full of energy, warmth and humor, her daughter Helena, a cool perfectionist, and Marianna, Zofia's beloved granddaughter, returning with her fiancé from a scholarship in the USA. The family drama begins when a flood wave floods the house, and at the same time grandma Zofia ends up in the hospital due to a stroke. An unfortunate coincidence leads Marianna to discover post-German traces in a house destroyed by the element, thanks to which she finds the diary of the first owner of "Home under Two Eagles", Lisa Weber. Marianna's learning of the history written on the cards takes the action of the series to 1918. In subsequent episodes, viewers will learn about the life of the then inhabitants of the tenement house and their neighbors.

Three-year-old Nikola Szlezyngier disappears in unexplained circumstances and her parents Angelika and Dawid are the main suspects. Angelika contacts an old friend Joanna Chylka, a brilliant, cynical and successful lawyer to help. With her new apprentice Kordian, Joanna will try to bring the case to a happy close.

During the Cold War, a local Polish officer and a young Soviet woman wedded to a Soviet officer are drawn together by music.