In Letter Sixty-six, which contains both Letters Sixty-four and Sixty-five, the Vicomte de Valmont writes to the Marquise de Merteuil, first to describe his recent interactions with Danceny with regard to the Cécile affair, and second, to reserve the right to sleep with Cécile if Danceny refuses. Valmont encloses the previous two letters to better document Danceny's behavior. Letter Sixty-four is a draft of a note to Madame Volanges in which Danceny apologizes for having upset her when she discovered his romantic involvement with her daughter. He refuses, however, to stop loving Cécile or to return her letters, as Madame had asked. Valmont notes, in his letter to Mertueil, that no matter how hard he tried, he was unable to convince Danceny to write otherwise. In Letter Sixty-five Danceny writes to Cécile herself. He asks her if she knows who betrayed their secret, swears his undying love, and also mentions that they should use Valmont as their go-between from now on.
Although she had promised never to write him again, the Présidente de Tourvel replies to Valmont's latest entreaty (Letter Sixty-seven). This final reply is meant to prevent Valmont from having any complaint against her. Tourvel offers him friendship and nothing more.
Valmont responds (Letter Sixty-eight) that he cannot simply convert his sublime love for the Présidente into friendship and that to ask him to do so is an insult to his feelings. Cécile, now deprived by her mother of all writing materials, responds to Danceny (Letter Sixty-nine) on a sheet of paper torn from one of his letters. She loves him still, and she is miserable. Also, she does not like Valmont, but she will suffer him, for Danceny's sake.
A new character has arrived on the scene, Valmont recounts. He is Prévan, who announced his intentions to seduce the Marquise de Merteuil at a dinner party Valmont attended. In Letter Seventy, the Vicomte warns Merteuil about this development. He also notes that the Présidente has at long last given in to him. He takes her offer of friendship as an indicator of her willingness to offer more.
In Valmont's next letter (Letter Seventy-one) to Merteuil, he describes his adventures at the Comtesse de B__'s country house, where he only just avoided being caught in a compromising position with her.
Meanwhile, the Chevalier Danceny writes Cécile (Letter Seventy-two) to tell her that he continues to adore her and that she should have more confidence in Valmont. Valmont himself attaches his own note (Letter Seventy-three), announcing that he has arranged for Cécile to have writing materials and that she should turn to him whenever she needs help communicating with Danceny.
The Marquise de Merteuil thanks Valmont for his warning about Prévan (Letter Seventy-four), but she tells him that, far from wanting to repulse Prévan, she welcomes his advances. Besides, she is beginning to tire of her current love, the Chevalier de Belleroche.
Cécile has indeed come around to the Vicomte de Valmont. In Letter Seventy-five she describes to Sophie in detail his kind regard for her and the subtle way in which he has arranged for her to correspond with Danceny.
Danceny and Cécile are now entirely under the influence of Valmont and Merteuil—and all by virtue of the elders' control over the young lovers' correspondence. Letters enclose letters; Valmont stands over Danceny's writing table; Merteuil tells Cécile what it is proper to say; and Valmont provides Cécile's writing materials. These are all ways in which the older couple dictates what the younger couple says. But the seasoned letter- writers are not only speaking for Danceny and Cécile, they are educating them as well. To the inexperienced, it must seem strange to transfer so much of one's passion onto paper. The rarified technique of conducting an affair in letters has to be carefully taught, a service which Valmont and Merteuil happily provide.
The conflict that develops between Valmont and Merteuil over Prévan is intriguing because the motives that fuel it are largely unknown. Valmont introduces an element into his correspondence with Merteuil that could only reflect badly on him. He tells her that she is desired by another, namely, Prévan, and that he does not want her to accept this new man's advances. Merteuil, who will seize any occasion to gain power over Valmont, naturally tells Valmont that she plans to welcome Prévan into her bedroom. There are a number of ways to interpret this situation. It may be that Valmont has overestimated Merteuil's debt to him for his proposed seduction of Cécile. It is also possible that, for some reason, Valmont wants Merteuil to sleep with Prévan. Merteuil must have anticipated this, and so perhaps her promise to accept Prévan's courtship is another front, designed to test Valmont's response. One thing is clear: since Valmont and Merteuil's own affair has for so long been carried out only in letters, once in a while they need to introduce new conflicts that involve their bodies, just to keep things interesting. Though the seduction of Cécile seems to be motivated by other factors, it is a similar kind of love-play for Valmont and Merteuil. They betray and manipulate as a kind of flirtation. It is their uncertainty of each other's motivations that causes them to continue the correspondence. Writing the next letter is both a way of forcing an interpretation of the letter one has received and a way of putting uncertainty back into the relationship. Beyond the letters, there can be no relationship for these two.