Four teenagers riot in the old town of Regensburg and threaten a younger couple. Max (Tilo Prückner) and Rike (Anke Engelke) rush to the victims' aid, and Rike is badly injured. Max takes up the pursuit of the young people. A short time later, Commissioner Lucas is called to a crime scene where the body of the only sixteen-year-old student Sebastian Holzinger (Martin Stürhrk), one of the four young people, has been found. Sebastian died as a result of a brutal fight in which Max, who is suspected of having committed a crime, was apparently also involved. Inspector Lucas' investigations initially focus on the other three students: Michi Schmidbauer (François Goeske) and his friends Miro Kovac (Edin Hasanovic) and Karli Sammer (Christian Reinhardt).
Under Sebastian's management, the boys run the Internet portal "pain attack", on the site of which videos recorded with mobile phones are displayed. "Happy slapping", as it is called in young professional jargon, fun films, but also violent videos in which mainly rich Regensburgers are denounced. OnA fragmentary and distorted film is found on the mobile phone of the murdered student Sebastian. The reconstruction of the video reveals a shocking truth: the high school student Diana (Nadja Bobyleva) was apparently sexually harassed by several young people, including Sebastian. For Commissioner Lucas the key to solving the case, but Diana, who has a strange love affair with Basti, remains silent - out of fear or solidarity - persistently. Then the investigators received the news that Günter, (Mathias Herrmann) the father of the dead boy, kidnapped the student Karli. He is firmly convinced that he has his boy's killer in his hands and threatens vigilante justice. Miro contradicts this theory and once again testifies that Max was the perpetrator, so that inspector Lucas has no choice but to as arresting their landlord. Then she gets wind that the students are planning a final coup. The action is to take place on a remote Danube bridge. Inspector Lucas rushes to the scene. Will she be able to prevent the impending catastrophe?

The teacher Eric Klausmann disappears into the forest. There is no trace of him or his car. When his dog is found shot dead, detective Lucas and her team must assume a violent crime. They begin their investigations in the teacher's private environment. The picture of the family idyll in the Klausmann house quickly crumbles. Last year Eric had a relationship with his colleague Lisa Hübner (Liane Forestieri), the best friend of his wife Nele (Karoline Eichhorn). Since then, the Klausmanns' married life has been troubled and Klaus Hübner (Johann von Bülow), Lisa's husband, jealously watches over his wife. His 16-year-old son Kevin (Sandro Lohmann) also has serious puberty problems. Kevin threatens to be expelled from school because of his rebelliousness and also has constant arguments with his father.
As a teacher, Klausmann seemed to be well liked by the students, while father and son had not spoken to each other for a long time. Ellen and her team investigate the causes of the teacher's disappearance. Her work is hindered by Nele, who investigates on her own and withholds important research material. Such a threatening email that she finds on her husband's computer, in which not only Klausmann is massively threatened, but also an attack on the school is announced.
Could it be that the popular teacher was kidnapped by his students or even became their victim? Did Kevin kill his own father? Or is the high school graduate Konstantin (Kai Michael Müller) behind it, a student from a good family, a member of the local rifle club, who organizes target practice with Kevin in the forest in his free time?