In 'The Murderer Lives at Number 21', a detective investigates a series of murders in a boarding house, where the residents and staff become suspects. The plot thickens as the detective uncovers shocking secrets and must race against time to catch the murderer before more lives are lost. With a mix of comedy and suspense, this French noir film keeps audiences on the edge of their seats.

Paris, France. Commissaire Wens is put in charge of the investigation into the murder of one of six friends who, in the past, made a very profitable promise.