Sensing that he’s Schnyder’s only possible pipeline into the Stasi, Falk refuses to agree to the blackmail. He tells Schnyder to make him a good offer and maybe they can do business.

Vera and Nicole ponder who the Stasi mole in the Democratic Forum could be. Falk orders his agent Frank Luchnik, the Democratic Forum’s representative to the Round Table talks, to stall for time. In the meantime, he starts making copies of all the important Stasi files and passes the information to Schnyder. Marlene tracks down Schmolke, the doctor who swapped Julia and Martin’s baby on Stasi orders, and learns the identity of the midwife who was on duty that night – Johanna Wagner. Together with Hans, they go to see her in Pankow, to press her for a sworn statement that the babies were indeed swapped at birth –  evidence that Martin can use to force the Simkows to have a paternity test for Anna. Falk gives Frank Luchnik a forged document stating that Robert Wolff had been a Stasi informant, which Luchnik presents to Vera and Nicole. They don’t buy it, and are now convinced that Luchnik himself is the mole. At a meeting of the Democratic Forum, the evidence against Wolff is presented, and Vera makes a startling confession about her own time as a Stasi informant. Her honesty turns sentiments against Luchnik, and the Forum nominates her as the new representative to the Round Table talks. Martin comes home that night, and Marlene and Hans present him with Johanna Wagner’s phone number – she’s willing to talk to him. Martin gets a sworn statement from Johanna about the baby swap, but his lawyer tells him that even with this proof, forcing a paternity test will involve a long legal battle against the Simkows. Martin is advised to speak with them again. Nicole and Vera get a confession from Luchnik, who says he was operating under duress. Vera asks him point blank if Falk is his Stasi controller. Marlene’s health problems continue, and she wants the entire family to spend Christmas together because she’s afraid that she doesn’t have much longer. She gets her wish – on Christmas Eve, the entire family gathers around the table one more time. When they are all together, Falk reveals that he has bought the house in which the family lives from the Ministry, so that his parents no longer need to worry about being evicted. Hans is touched and, for the first time in years, embraces his son. Johanna Wagner calls Martin again and meets with him to tell him that she recognizes Falk’s picture in the newspaper as the man who ordered that his daughter be swapped all those years ago.

Martin is stunned. It was his own brother Falk who ordered that his daughter be swapped. He now suspects that Falk was also responsible for Julia’s death.

Following a deal with his police friend Görlitz, Martin gets his hands on the file of Julia’s accidental death and finds inconsistencies there, too. Beside himself with rage, he goes to confront his brother. Marlene is very concerned about Martin and is no longer sure that discovering the truth about Anna’s disappearance was the right thing for him. Falk offers Schnyder tape recordings with information on West German politicians. In return, he demands immunity for himself and his father in the event that the political system in the GDR breaks down completely. But Vera is hot on his heels, too. In order to support Martin further in his claim for a paternity test, Katja looks into the whereabouts of Dr. Maiwald, the doctor who supervised Anna’s birth. Her informants tell her that the doctor now lives in London. In the meantime, for their own peace of mind, the Simkows have had a paternity test. When they discover they are not Anna’s biological parents they, like Martin, are completely overwhelmed by the situation. And just as it began with the fall of the Berlin Wall, the season ends with the storming of the Stasi headquarters on Normannenstraße by thousands of demonstrators on January 15th, 1990. Martin is with them. In Falk’s office, the two Kupfer brothers finally meet face-to-face…

Season 4 of The Weissensee Saga is planned to begin production in Berlin next year, for a 2018 premiere.