In the early hours of the morning, Julia Marschner, who was still celebrating at a "over 40 party" that night, was found dead in the park. She has been strangled. The situation at the crime scene reminds chief inspectors Eva Saalfeld and Andreas Keppler of a past case. Did the "strangler from Mockau Ost" strike again or did the murdered woman, who has traces of shackles on her hands and feet, die in an unusual love game? Julia's friends, the physiotherapist Karmen Slowinski and the lawyer Silvie Stein, tell of a man who hassled Julia on the dance floor the night before. Did Julia go home with this stranger? The detectives question Julia's 20-year-old daughter Caro, who tells of an affair her mother had with a flirting teacher.
Tom Römer vehemently denies this relationship with the murder victim, but gets caught up in contradictions during his interrogation by Keppler and is taken into custody. The inspectors determine that Caro's charming and slightly older friend Mike had long-term telephone contact with her mother Julia on the night of the crime. Julia didn't like her daughter's relationship with Mike and she wanted to get her to end this relationship. Did Mike attack Julia to prevent that? Meanwhile, Tom Römer tries to pull his head out of the noose and claims that another regular at the "Ü40 party" left it with Julia: Peter Hauptmann. However, the reputable cosmetic surgeon seems to be happily married to his wife Annika.
Although Annika Hauptmann gives her husband a watertight alibi, the inspectors use a search warrant to gain access to his second home. In doing so, they come across a delicate secret that has apparently affected their circle of friends more than they want to admit...