An uncle in America wants to endow his nieces with a dowry, provided they succeed in making a name for themselves one night at the Moulin Rouge, where one of them is already performing. Everyone's pulling out all the stops to help the girls put on an act, dupe the theater manager and win the dowry - which will be doubled if they manage to marry, as their uncle is marrying the star of the show.
The Raffin Commissioner investigates the murder of an industrialist and it soon becomes apparent that the activities of the relatives of the deceased all revolve around the Folies-Bergere.
On her way to Paris, Gisèle meets a young motorist who offers to be her guide. Gisèle, suspicious, refuses and disappears. But Pierre finds her and takes her to dinner at Saint-Germain-des-Prés. On the other hand, Gisèle, out of jealousy, goes off on her own to visit "Paris by Night", showing us some of the attractions of the "Moulin Rouge", "Naturistes", "Rock and Roll", etc., etc., etc. Pierre pursues her and eventually discovers her hotel. The next day, he takes her for a walk around Paris. They dine at an inn where a supposed car breakdown forces them to spend the night. There was only one room, but the virtuous Gisèle locked Pierre in the bathroom. All ends in the most honest engagement in the world.
A young woman has been run over by the car of Carlos, a brilliant embassy attaché. Feeling sorry for her, Carlos drives her to his place and decides to take her in. The young lady accepts his offer but refuses to tell Carlos her name, wanting to be called Miss Pigalle, after the Paris district where she was born. It does not take long before Yvonne (Miss Pigalle's true name) and Carlos fall in love. Life is like a dream and, when Yvonne gets pregnant, their happiness is at their peak. Unfortunately, a revolution breaks out and Carlos returns to his country in secret. Feeling forsaken and at a loss, Yvonne, who is now penniless, has no other solution but prostitute herself.
