The Présidente is understandably annoyed by Valmont's conditions. She replies in Letter Forty-three that she will not reveal her sources, though she does give in to his second request that he be permitted to write to her.

This cold acceptance of his second request is good news to Valmont and he interprets it as a sign of Tourvel's secret love for him. He has finally succeeded in reading her mail, as he informs the Marquise in Letter Forty-four. Having forced the Présidente's maid into a compromising situation, he blackmails her into stealing her mistress's letters. He is pleasantly surprised to note that Tourvel has kept all of his letters and that she even pieced back together one that he had earlier seen her tear up. He also discovers that it was Madame Volanges who had been spreading nasty rumors about him. He resolves to seduce Cécile in revenge.

Letter Forty-five brings news of Valmont's departure, and the Présidente de Tourvel's relief, to Madame Volanges.

Letter forty-six is a saccharine love-note from the Chevalier Danceny to Cécile. As usual, he is begging her to prove her love to him.

Back to Valmont's activities: Letter Forty-seven is another letter within a letter, this time a message from Valmont to Tourvel, which will travel by way of the Marquise. In the portion of the letter addressed solely to the Marquise, Valmont recounts an exciting evening he spent at the house of a courtesan named Emilie. In fact, he announces, he is using her naked body as a writing desk at this very moment. Reading the letter to Tourvel, the Marquise will note several veiled references to the erotic manner in which it was composed.

Letter Forty-eight, written after passion, is full of passion and hyperbole. The Présidente, Valmont swears, should never have cause to doubt either the sincerity of his love or the depths of his suffering.