Letter thirty-three returns us to the correspondence of Madame de Merteuil and the Vicomte de Valmont. Merteuil is writing to Valmont to inform him that he is using the wrong tactics entirely to seduce Tourvel. She tells him that he should stop writing letters and starting speaking to the Présidente, since in his writing he is only defeating himself.
Valmont replies (in Letter Thirty-four) that he is having difficulty either seeing Tourvel in person or getting her to receive his letters. He has finally had to resort to the trick of falsifying a Dijon postmark and having one of his servants plant his letter in the mailbox. Since Tourvel's husband lives in Dijon, she will naturally be required to open this letter. On the day that she does, at breakfast, she tears up the letter in disgust upon reading it. Valmont notes that she does take care to hide the pieces in her pockets.
The next two letters (Letters Thirty-five and Thirty-six) are the two most recent letters from Valmont to Tourvel. The first is returned to him unread; the second, mentioned above, is the one postmarked Dijon. They are both filled with language designed to seduce and ensnare, and both relate little of everyday events other than Valmont's amorous suffering.
The detailed psychology of the characters/authors of Dangerous Liaisons is especially clear in this group of letters. Cécile foreshadows this theme by remarking in Letter Twenty-seven that it is almost as if the Marquise de Merteuil had read her mind. This mind-reading on the part of the Marquise de Merteuil is in fact a special technique of citing the conversation or writings of others in her own conversation and writing. When it seems that the Marquise de Merteuil has read someone's mind, she has in fact only repeated what others have told her. It is not necessary to be able to read minds when one can read countenances, or letters, so well.
It seems probable that the Marquise de Merteuil has written many of these letters herself, even if someone else's name is signed at the bottom. Both Danceny and Cécile are thoroughly in her power, and she creates their love affair very skillfully. The desire to see someone else express his or her desire is one theme of the Marquise's machinations. The Chevalier Danceny's letter to Cécile (Letter Twenty-eight) is a perfect example, especially since we have reason to believe that the Marquise is composing his letters for him. His request for an affirmation of love from Cécile is in fact a request from the Marquise. We can also see the Marquise's hand in Letter Thirty, especially in Sophie's awkward admission of love to Danceny. Danceny's reply (Letter Thirty-one), containing a paragraph about how he sees words of love dripping from Cécile's eyes and mouth, is so ironic in its praise of the authenticity of Cécile's affection that we can imagine the Marquise de Merteuil laughing as she composes it. Cécile's words of love are the Marquise's words, just as Danceny's words are the Marquise's words. Their affair is Merteuil's composition, itself a grand letter.
The Marquise also attempts to dictate the terms of Valmont's affair with Tourvel. In Letter Thirty-Three she warns him about using too much logic in trying to corner the Présidente in his love-notes: "Above all, the presence of the beloved is a check to thought and an incentive to surrender" ("...la présence de l'objet aimé empêche la réflexion et nous fait désirer d'être vaincues"). But it is unclear whether the Marquise's suggestions are intended to help or hinder Valmont in his efforts. If she suggests that Valmont should stop writing to Tourvel, it might be because his letters are bound to succeed. His reply acknowledges this irony, "Your letter was splendid, my love, but why exhaust your energies in proving what everyone knows?" ("Vous parlez à merveille, ma belle amie: mais pourquoi vous tant fatiguer à prouver ce que personne n'ignore?"). This means both that he acknowledges the validity of the Marquise's advice and that he has noticed that she is making a special effort to prove ancient cliché true—a double-entendre and an insult she will understand if she is reading with her own letter in mind.