Eloi is a twenty-year-old secondhand goods dealer who does his job without particular enthusiasm. He has a girlfriend, Nénette, but immature as he is, he feels just as happy in the company of Fortunée, his young sister, whose little girl's games he shares as often as he can. The three of them live with Eloi and Fortunée's grandmother, nicknamed by all the "Queen of the Flea Market". In possession of a mirror of Venice, Eloi decides to present it to Dormoy, an antique dealer who keeps up shop in the fashionable districts of Paris. On that occasion Eloi meets and falls in love at first sight with Dormoy's rich mistress. The latter, half-moved, half-consenting, does not discourage him...