Writer Johannes Pfeiffer who goes undercover as a student in a high school after his friends told him that he missed out on a great life experience since he was home schooled.

Research results of enormous value are stolen from the experimental laboratory of a chemical company in the fictitious town of Bärenfurt in the GDR and seized at the Berlin sector border. The trail leads to the agent "Haas" at the Bärenfurt municipal theater. Captain Jentsch is at the theater to uncover his identity and arrest him. A murder takes place during the "Fiesco" premiere. Many people are suspects, including the head of the theater, Born, who is engaged to the actress Vera and has a conspicuously apolitical attitude. It is no easy task for the security officers to distinguish between reality and appearance in this milieu. Through precise work, they succeed in unmasking the perpetrator and arresting him after a chase through the theater.

The construction of five houses for a workers' housing cooperative has been delayed due to a shortage of workers. It is winter and it is foreseeable that the houses will be completed in the fall at the latest. However, this takes too long for the young electrician Gustav. He is frustrated and wants to finally live within his own four walls. So far, he and his wife Christl, a sales clerk, have been subletting from his parents-in-law. One day, he receives a visit from his Aunt Minne, who informs him that he has inherited an apartment building worth 12,000 marks from his deceased Aunt Erna. He rejoices, as a house is even better than an apartment and he no longer needs to be a member of the building cooperative. The house turns out to be a dilapidated old building with no furniture and no water or electricity. Christl refuses to move into the building and begs Gustav to turn down the inheritance.

Railway employee Fritz Marr is not regarded well by his superiors. It is the year 1920, and trains regularly pass the railway hub of Erfurt to the East to secretly transport weapons for the fight against the young Soviet Union. Marr knows about this and wants to mobilise other workers to stop these illegal deliveries. To muzzle him, Marr is relocated to a remote rail work construction site.

A mechanic, Peter Papenbold, is giving all his free time to volunteer in the children's sport school. When he's asked to switch to teaching permanently - it's a very difficult decision for him.

In this the fourth episode, “Battle of Berlin,” the Soviets start their assault on Berlin, and Stalin negotiates with the other Allies.