Pierre Tercelin who used to be a prosperous industrialist is now ruined and embittered, having become a mere lock keeper. A widower, he lives with his daughter Evelyne, a music-hall dancer. Claiming he is being persecuted by his cousin Edgar he gets in touch again with another cousin of his he hates, Bernard, a millionaire gun runner,who is also a victim of Edgar. It must be said that both Pierre and Bernard once caused Edgar to go bankrupt... Pierre offers Bernard to join efforts against Edgar. Soon after, Bernard dies of poison, which is only the first of a series of acts of violence. Tiercelin is shot at while going back home, Bernard's son is gunned down while his sister Luciane disappears. Chief-inspector Malouvier - who oddly enough looks very much like the suspect- investigates....
Tongues start to wag after a famous Parisian music hall dancer is rushed to hospital after being found poisoned by arsenic at the Concert Mayol.
A young customs officer is given an important mission: to investigate drug trafficking on the Belgian border. Incognito, he goes to the place where he easily spots the gangsters.
Sylvette welcomes three soldiers on the eve of Saint-Jean 1945. Each claims that she promised him five years earlier to belong to him on Saint-Jean... Which one is the right one? Finally, it is Francis who manages to prove his good faith. Sylvette will be, we couldn't be happier to get rid of a flighty husband who has gone to look for the damsel in the four corners of the world...
For the Marquis Barbezieux de Saint-Rosay, nobility is important. If anything can comfort her, it's her family tree. In order to erase any doubt he invites in his castle a cousin of his established in Scotland, whom he instructs to bring him his titles of nobility. A first person introduces himself, calling himself his cousin, but it's not him. Then one, then two, then three false cousins appear in turn. Will the real Saint-Rosay of Scotland eventually present itself?
Mimile is a street singer and also a very inventive free rider. With his friend Georges, a musician in the same orchestra, they meet Arlette Sicleton and Lulu. Arlette is the sister of Sicleton, a sports event organizer and Lulu is the daughter of Ledoux, the supervisor in charge of tracking down free riders. After many misunderstandings, love will triumph.
Miquette is a young woman whose beauty and vivacity increase the clientele of her mother's tobacco shop. A Barrymoresque actor believes that Miquette has star potential, but he hasn't sufficient capital to finance her theatrical debut. He manages to get the money by practicing a bit of genteel blackmail on an aging marquis who has romantic designs on the heroine.
When her fiancé breaks off their engagement, Danielle leaves London and returns to her mother, Jenny, in Paris. With her business partner Benoît, Jenny runs what appears to be a respectable nightclub – it is in fact a place where wealthy men can buy the favours of attractive young women. Oblivious to her mother's professional and personal life, Danielle meets a handsome young man named Lucien, and falls in love with him – not realising that he is Jenny's lover...
Robert Bernier murdered his brother with the complicity of a worker. The only witness to the tragedy, Veronique was injured while rescuing her boss and remains blind. Later, cured by an operation, she denounces the criminal whose voice she recognized and who had taken over the factory.