Thirty-year-old computer scientist, physicist, bachelor, sickly shy and hypochondriac, Claude Mandelbaum leads a life all the more dull that his last, and only, love story goes back two years. One day, on the occasion of the marriage of his best friend, Daniel, he meets Serge, a divorced fifty-year-old who takes full advantage of his celibacy by chaining the adventures. Shortly after, on the advice of Daniel, Claude resolved to make an appointment in a marriage agency of a particular kind, where it is the women who contact the men. In the waiting room, he falls face to face with Serge, who invites him to have a drink in his home ...