Anita Holz is still happy. The wedding with Konrad Lenzen is imminent, they have waited a year after the death of their husband. And Konrad wants to put his inheritance into her taxi company to save her from bankruptcy. Then she can finally get rid of her biggest creditor, Erich Blacher, the largest taxi company in Stuttgart, who has been targeting her business for a long time. But Anita Holz' happy future is gone when Bienzle is called to a crime scene: Taxi driver Konrad Lenzen has been stabbed. His wallet is empty, a robbery is likely - but a year earlier Gerhard Holz, Anita's husband, died in exactly the same way. While the search for the last passengers from Lenzen begins, Bienzle and Gächter interrogate Anita Holz, who is trying to regain her composure.
In addition to the grief for her fiancé, there is economic pressure. In the tough competitive situation of the taxi companies, the Holz company got heavily in debt. The murder of her husband was filed unsolved - the same perpetrator may have struck again. This is exactly what scares the taxi drivers. Whether they belong to Holz, Blacher's company, or are self-employed, they all fear a serial killer targeting taxi drivers. More than one of them gets frustrated when a passenger looks suspicious at night. Erich Blacher, on the other hand, can triumph because Konrad Lenzen's death gives him access to the Holz company.
Of course, the files of the old case are examined again and Bienzle can't help but notice that his colleague Gollhofer, who has meanwhile retired, worked rather sloppily. But Gollhofer has retired to his winery on the hills of Stuttgart and no longer wants to be addressed about old cases. Not a good role model for Bienzle, who has just received the news that he is to be appointed as his successor as chief detective. His joy is clouded because Hannelore sees the promotion as a reason to force a new suit on Bienzle – but no reason to accompany him to the appointment ceremony.
But that is canceled anyway, because another stabbed taxi driver is found: Thomas Breuer, a driver who studied law and who often loudly criticized the working conditions in the taxi business. In the Taxistüble, the drivers' traditional meeting place, talk of vigilantism is getting louder.