Two young men, one shy and one self-confident, spend a fast-paced night in Paris trying to pick up chicks. They confront every possible difficulty

A small-town policeman is informed that "naked women" are dancing in a revue at a local variety theater. Being the guardian of public morals that he is, he decides to stroll on down there and check it out for himself.

An unscrupulous young man uses his "fiancée", who haunts gambling halls, to recruit the collaborators he needs to pull off his scams. When these unlucky gamblers are driven to dishonor by debts, he has his fiancée lend them money, and the next day he has them write checks, which of course bounce. All they have to do then is walk straight ahead, her charm encouraging them to do so. But the carefully planned hold-up at the home of a wealthy American tax dodger is a fiasco. The thief finds the safe already emptied by the very man who reported the bargain. But the unfaithful informer is fooled in turn: the loot he was about to take away in an Air-France suitcase is innocently snatched by a group of nuns who take the wrong luggage and unknowingly take off with 500 million dollars.

Young provincial Charles arrives in Paris to stay with his cousin Paul while studying law. Paul is a decadent, bohemian pleasure-seeker who shows the meek, diligent Charles the thrills of city life. When Charles falls for Florence, one of Paul's acquaintances, relationships begin to shift.

Lucien, a modest engineering student, discovers that his steady girl friend Mireille is using him to cover up her dates with Mario, an older man. Lucien wanders about the streets of Paris and meets Joëlle, a sophisticated teenager who supports herself with a job in a sleazy nightclub. It is late when they meet, and Joëlle invites Lucien into the club and demonstrates her stripping act to her one-man audience. A feeling of rapport develops as they go from place to place seeking entertainment; in the morning the two discover they have fallen in love. Mireille learns of the romance and, on a bet, plots with Philippe and other friends to break up the affair. Neither Lucien nor Joëlle, however, succumbs to the propositions of Mireille and Philippe. Later at a nightclub, Mario gives the appearance of seducing Joëlle. Enraged, Lucien rushes at him and they fight. Lucien is reunited with Joëlle--he has learned of the complexities of love, and she has acquired from him a sense of stability.

Martine is a young woman plagued both by poverty and by uncaring, problem parents who in no way can provide the kind of nurturing that Martine needs during her adolescent years. As a result of her family situation, Martine runs away from home and gets involved with a group of teens and young adults from the wrong side of the moral tracks.

During a plane crash, Professor Sellier, an atomic scientist carrying very important documents, dies and his papers are stolen. Bordy, a sergeant in the Second Bureau, is asked to take Sellier's place in his family's home, in order to make the kidnappers believe that he is not dead.