In the case of a serial killer, Inspector Vorobechik, known as Wens, is assigned to solve the mystery. The killer leaves a signature calling card on each victim, and Wens' mistress, Mila Malou, a struggling actress, decides to help him to gain publicity for herself.
The Murderer Lives at Number 21
A retired detective, Inspector Wens, relocates to a Parisian boarding house to track down a ruthless serial killer, only to find himself immersed in a complex web of clues and suspects.