An unbelievable fact: On a walk through Munich, Ayumi Schröder, her husband Ben and their six-year-old son Taro saw a man lying in front of a bank branch who seemed to be looking for help. Ben thinks he's drunk and wants to help him when the stranger stabs him multiple times out of nowhere. Just like that, for no apparent reason. Ben collapses, bleeding, in front of his Japanese wife, son and numerous witnesses. The perpetrator is able to flee, and a short time later Ben dies in the hospital. Batic seems nervous, not only because of the horrible act. He hardly sleeps anymore, is irritable and off track. The encounter with Taro and his mother finishes him off. Maurer puts Leitmayr in charge of the Soko. He too has noticed that Batic isn't quite up to speed at the moment.
Questioning the countless eyewitnesses reveals a confusing puzzle for the inspectors. Because despite the many reports, there are no concrete clues for their investigations, because everyone saw the crime and the perpetrator differently. Everyone has their own truth. Almost nothing useful emerges from a large number of observations. But then a first success: a handkerchief from a garbage can near the scene of the crime, a splash of the perpetrator's blood, a DNA trace. Leitmayr orders a mass genetic test. Thousands of men who were in the vicinity of the crime scene at the time of the crime and could be identified via their cell phones have to submit a saliva sample. Under high pressure, Leitmayr, Batic, Kalli and Semmler are sitting with numerous colleagues in a converted police gym and taking rehearsals.
For weeks without a match, without success. During this time, Ayumi Schröder comes to the station almost every day to make new statements about the crime. She keeps coming up with new details. When Maurer finally dissolves the Soko due to lack of success without the perpetrator being caught, the investigators' nerves are on edge: "That bastard is still running around out there." Together with the case analyst Christine Lerch, Batic and Leitmayr go back to the crime scene and investigate something that may have been overlooked before. Lerch develops the thesis that the perpetrator lives close to the scene of the crime and that he planned the crime for a long time. He kills for pleasure and not for any specific motive. Local residents are once again the focus of the investigation.
Ayumi Schröder can hardly stand it any longer, she finally needs clarity as to why and by whom her husband was killed. Batic advises her to return to Japan. But she can't. She needs certainty. Then a second murder occurs that appears to be related to the first.