In the summer of 1989, Barbara Neder, the sister of Hamburg state police chief Thomas Bethge disappears without a trace from her home in Lower Saxony. Shortly before this, two terrible double murders are discovered in nearby woodland. The local police seem overwhelmed by the situation. Only the young inspector Anne Bach, who sees Thomas Bethge as a mentor, believes that the crimes are connected...

State police chief Bethge promises his worried mother that he will find his sister who has disappeared without a trace. But the investigating police officers resist what they see as his attempts to interfere in the case and remind the Hamburg detective that he has no jurisdiction in Lower Saxony. Instead, the police officers first suspect an act of revenge against Bethge himself but then come to s..

There is still no trace of Barbara Neder. Her family is desperate and tries to search for her with the help of a TV show – without success. Meanwhile Barbara’s mother attempts suicide. Theresa Neder – the daughter of the disappeared – suspects her father. After the young policewoman Anne Bach has studied all the files again, she concludes that everything is pointing to the..

Anne Bach convinces the public prosecutor's office to agree to raid the house of the cemetery gardener Jürgen Becker. The house contains weapons, handcuffs and other items used to keep people prisoner. In the garden, the police dig up a buried car. Even though the cadaver dogs pick up a scent, there is no trace of Barbara Neder in the car. Jürgen Becker learns about the police operat..

Together with a private investigative team, Bethge reopens his sister's case after his retirement. He obtains all the files and manages to get into Becker's "secret" room once again. There, even many years later, overlooked evidence is found, supporting a grave suspicion. Was his sister the victim of a mysterious serial killer? Inspired by real-life-events that took place the la..

A new witness describes Jürgen Becker as a sadistic and unscrupulous seducer who has tried to make money in every conceivable way. Anne Bach, together with Thomas Bethge, draws up a profile of a psychopathic serial killer. Once again, Thomas Bethge takes a look at Jürgen Becker's farewell letters, in search of the secret of his missing sister. Will he find what he has been looking fo..