Nénette, a promiscuous pipe-smoking girl, loves Claude, a gangster who has just pulled off a gainful heist. They both drive to Le Havre from where they plan to set sail for Desirade Island. But in Le Havre, Claude meets Raymond, a shipyard worker and former vet friend of the Indochina War, who offers to accommodate him. Claude accepts but, as a token of his "gratitude", he seduces Raymond's wife. In despair, Raymond, who in the meantime has lost his job, jumps off a cliff. Shadowed by a detective, Nénette becomes his mistress, knowing full well that Claude will be arrested because of her.

The story is based on Voltaire's tale "Le monde comme il va" ("The world as it is"). Sent by the genie who presides over the destiny of Persepolis (Paris!), the Scythian Babouc carefully informs himself of everything, to tell the genie whether or not to destroy the city. This is the pretext for a series of interviews, scenes taken on the spot or reconstructed in the studio. We meet a musician who lives for his art and a Marxist historian, both of them optimists in the end; but also a war widow and an economically weak old lady: while the "fureur de vivre" gives free rein to the Golf Drouot and socialites hide their turpitudes behind a façade of good manners. A large, poorly housed family bravely faces up to its fate, and the children are happy; a working-class household talks about the union struggle, inhumane working conditions and reasons for hope. Finally, a poet sums it all up by talking about his commitment to the service of mankind.