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.
Monsieur Benoit's existence is transformed when his dour wife suddenly thinks in a bout of folly that she will become a chanteuse and her husband the impresario.
Antoine Mouret, an authoritarian restaurateur, is the head of a large family where, for reasons of interest, people only marry cousins. But some have other plans, Marcus especially when he meets a passing circus girl.
