Alarm in Düsseldorf: the body of a nurse has been found on the banks of the Rhine, and evidence at the crime scene recalls a series of murders that had terrified the area four years previously. Three women had been killed in exactly the same manner. The obvious connections to the old cases prompt the head inspector to appoint Helen Dorn as chief investigator. In order to solve the nurse's murder, the old cases must be reviewed, whereby Helen and her partner Georgi come upon suspects from among their own police colleagues.

A missing child is at the center of Inspector Helen Dorn's investigations. Mia, the four-year-old daughter of the wealthy businessman Hans Thomsen, has disappeared under mysterious circumstances. The family members are under shock; a kidnapping seems likely. While Mia's mother Inga tries to keep the family together and prevent an escalation, her husband wants to find his daughter on his own. But why does he head so assuredly for Rotterdam? After a difficult start at police HQ with her new partner Gregor Georgi, Helen Dorn begins to discover some very surprising things about Gregor. He, meanwhile, sets out to understand Helen better by uncovering her past…