While jogging together, Christina stumbles upon the body of asset manager Peter Münch. How he died is initially unclear, as there is a strange wound on his neck. The question of where the victim was before his death is also not easy to answer.

While his widow Erika Münch believes he was at the community center attending a support group for overweight people, the "Festen Freunde" (Close Friends) – as the group is called – claim that Peter Münch had not attended their meetings for weeks. It also quickly becomes clear that the deceased had no real friends among the members and that there is generally a tense atmosphere within the group. When it emerges that the group's initiator, Frank Leibnitz, has also stolen money from the group's joint fund, the situation threatens to escalate completely.

Girwidz, however, is only half paying attention; he has completely different problems: in a few days, he has his MPU (medical-psychological assessment) and hopes to finally get his driver's license back. He hasn't told his colleagues yet – in the unlikely event that he fails, he doesn't want to embarrass himself. However, when he learns during the investigation at the community center that special courses are offered to prepare for the MPU, he panics and wonders if he is really well enough prepared. Because time is running out, Yazid is supposed to fix it with a crash course.

Meanwhile, Hubert and Christina discover that the deceased had incurred the wrath of some clients in his role as asset manager, most notably Frank Leibnitz from the "Festen Freunde" (Close Friends) ...