In the fourth episode of "Unfamiliar," the story unfolds with Simon and Meret reflecting on the unforgivable decision they made by leaving Katya with Josef. Meret candidly admits that she had always planned to do so. Just then, both Katya and Nina appear at their doorstep. Simon orders Nina to go to bed, unaware that Katya has realized that Nina is her child and is now in a state of distress. Simon, in an attempt to calm her down, knocks her out and takes her to the safe house.
Meret speaks to Nina about Simon's aneurysm, assuring her that he will be okay. She also shares a story about her older brother, who took his own life, but her family insisted it was an accident. She expresses her admiration for Nina's refusal to accept lies, in contrast to her own life, which is built on them.
A flashback takes us to Morocco, 17 years ago. Meret is on a mission to target a sheikh but is also having an affair with Jonas. While on the phone with Gregor, she requests two extra weeks in Morocco after this mission. She sneaks into the sheikh's residence and copies his phone as the alarm bells start ringing. The sheikh's head of security, Jonas, ends up chasing and holding Meret at gunpoint.
In the present, Meret heads out to get information from Jonas. She rings the fire alarm at his office to bring him out. He confesses that he didn't know she was the target and that he's tried to walk away but hasn't been allowed to. She sneaks him a paper with the name of a hotel on it.
Back in the past, Simon confronts Gregor about Meret needing two more weeks in Morocco. Gregor tells him that Meret asked for it and bluntly states that Simon's marriage is dead. In the present, Ben and his team are investigating the location of the shootout from the previous episode. Meanwhile, Josef has dumped Gregor out in the middle of nowhere.
At Simon's restaurant, he assures Nina that he will undergo surgery for his aneurysm. However, he is distracted by a security alert at the safe house, where Katya is destroying the security cameras. Simon goes there and apologizes to her as she hits him repeatedly.
Jonas goes to the hotel to meet Meret and they end up sleeping together. A flashback reveals that Jonas killed his colleague and helped Meret escape from the sheikh's estate. She begged him to run away with her, but he refused.
At present, Simon shares with Katya the story of how the poison caused Nina's chronic kidney failure. She underwent a transplant, and only the last few years of her life have been healthy. Suddenly, Simon receives a call from Gregor, who was able to flag down a young boy passing by on his bike. Simon gets his location and they rush to his aid, only to find Gregor bleeding out.
Meanwhile, at the hotel, Meret and Jonas are in bed together. Meret asks him to help her take down Josef, but he refuses, saying that Josef's father-in-law, Sasha, is even more dangerous. At the same time, the BND taps the phone call between Gregor and Simon and gets a pin on his location.
As Simon ties a tourniquet to Gregor's leg wound, the latter reveals that Josef has a mole in the BND. Katya accuses Gregor of leaving her for dead and removes the tourniquet. Simon simply allows her to do so, even as Gregor passes away. While driving back, they cross Julika's car and she recognizes Simon as Karl. A chase ensues but Simon manages to lose Julika. However, the car is registered to their home address. And if the BND has a mole, they're all in danger.
In the hotel room, Jonas goes for a shower and Meret uses the opportunity to copy data from his laptop. However, Jonas isn't really taking a shower. He's putting together a gun. He holds Meret at gunpoint and uses her phone to figure out her home address, and sends the location to Josef.
Simon and Katya arrive at Simon's restaurant and he tells her to wait while he gets Nina and Yul from inside. Julie and Alice arrive, soon followed by Josef and his people. Simon and his gang get away and so do Josef and his people, to Julika's annoyance. At that moment, Julika gets a call saying that Gregor has been found dead and Alice comforts her. Julika also gets an anonymous text saying that the BND has a mole.
The episode ends with Simon and his group reaching the safe house, while Jonas has Meret tied up in the hotel room.
