Her father has been dead for 15 years, but the unsolved murder doesn't leave Chief Inspector Ann Kathrin Klaasen in peace. Worried, her colleague Frank Weller urges her to go to the doctor. In practice, she experiences a huge surprise: in the waiting room, she sees a photo of her own father in an old lady's wallet, together with a woman she does not know. Even if Gertrud Klocke asserts that the man in the photo is her deceased daughter's fiancé, there is no doubt for the inspector. Ann Kathrin cannot forget the encounter. Therefore, she looks for Mrs. Klocke again in the retirement home, but finds the old lady lifeless in a beach chair.

Ann Kathrin Klaasen and Frank Weller have to solve a case involving a woman's corpse in the moor. But it doesn't stop there: In addition, the kidnapping of six-month-old twin babies is stirring up northern citizens. Frank Weller misses the right moment for his marriage proposal. Because he and his girlfriend, Commissioner Ann Kathrin Klaasen, are drawn deep into a particularly grisly case. The body of a young woman has appeared in the Uplengener Moor. Ann Kathrin Klaasen wonders why the perpetrator made so little effort to sink the victim properly. It almost seems like it should be found.

Ubbo Heide, the retired former head of the Aurich criminal investigation agency, receives a package. Inside is the severed head of a former prime suspect who was never convicted. On closer inspection, Ubbo recognizes Bernhard Heymann, who was the main suspect in the murder of his own daughter, six-year-old Steffi, a few years earlier. Rupert finds out that the parcel was posted by a woman in her mid-30s. The sender's name and address turn out to be fictitious. Ann Kathrin Klaasen and Frank Weller go to Ubbo to examine the severed head. The images from the surveillance camera at the post office show a petite woman looking around anxiously in the queue at the counter. Marion Wolters finds out that the woman is Svenja Moers and was suspected of poisoning her husband five years earlier. Due to a lack of evidence, she was released at the time. She hasn't been seen for days now, and Ann Kathrin puts out a manhunt for her. It seems she has been kidnapped. Who is behind her abduction?