The fifth of Eric Rohmer's projected cycle of "Six Moral Tales" (My Night with Maud being the fourth), this film is yet another variation upon the theme of love.

Jerome, a handsome, worldly diplomat, who shortly before marrying Lucinde, the woman with whom he's been living on and off for six years, takes a holiday in the village of Talloires near Annecy.

There he meets Aurora, a novelist who was once his mistress, and the two daughters of the family with whom Aurora is staying. The girls are sixteen-year-old Laura, who immediately declares her love for Jerome, and her elder step-sister, Claire, in love with Gilles, a boy of her own age. Aurora informs Jerome of the situation, and persuades him to take up the challenge. After a brief flirtation with Laura, both lose their desire to continue the game.

However, by now, Jerome finds himself becoming physically attracted to Claire, her slim figure and slender limbs, but most particularly her knee. But Claire is indifferent to him and the challenge becomes more complex.