23 murders in Berlin - and one confessor: Maximillian Rapp has confessed to the crimes and is sentenced to life in prison. The BKA investigator Tara Schöll, however, has doubts about the guilt of the serial killer. For at least one of the acts, Rapp's alibi is watertight. Tara and her partner Henry Kloss want to convict the real murderers in the highest secrecy. Rapp surprisingly offers his help - and now tells more than he once put on the record.

Since Maximilian Rapp went into hiding and the body of the customs officer Sass was found, Tara was held responsible. She is promptly suspended, but this does not prevent her from continuing to search for the girl's real killer. Together with Rapp, she returns to the victim's apartment, where an important, new detail catches her eye.

Tara and Henry take on the case of the Schächter brothers who were murdered in a forest hut. Rapp, who once took responsibility for this, is working closely with them again. When Tara, Henry and Rapp return to the crime scene, Henry is attacked by a stranger.

Tara and Henry tackle the obscure death of Mr. Willcke, who was murdered in a crematorium. She insists on having Rapp continue with the investigation. In search of new clues to the real murderer, Rapp spent the night with the responsible policeman Weiser at the crime scene. A few hours later, Weiser is found dead. Rapp is under suspicion, but can not remember anything.

Tara Schöll and Henry Kloss reopen the harrowing case of Helena Husek. The young woman was tied to the bed in a bungalow by the lake and found dead. All the evidence pointed to her lover Christian Bohn and made him the main suspect. His wife Bärbel gave him a waterproof alibi for the time of the crime. At that time, Rapp surprisingly stood before the court.

Maximilian Rapp finds a piece of paper on which an urgent warning to BKA investigator Tara Schöll is written. Since her father Robert's supposed suicide, Tara has been plagued by feelings of guilt. Rapp knows better now: Robert Schöll is not dead, but still alive.