Private eye Roland Wilhelm was fatally stabbed, the corpse burnt in his car. The heir, youthful-bullied brother Markus Wilhelm, runs with wife Bianca an ailing book shop, she's also a night cleaner. Roland Wilhelm was hired by the under-staffed tax office to investigate fraud suspects, including night-lifer Klaus Bühler, who has an alibi: Helga Fischer's nightclub annex brothel and illegal casino. *Wilhelm found out Markus and Bianca spends beyond their official means, from her actual night job in the brothel. His papers also contain a file on commissioner detective Jo Stoll who investigates informally.
—KGF Vissers