After his meeting with Milady, the cardinal returns to the common room of the inn where he finds Porthos and Aramis playing dice. He asks the two musketeers what happened to Athos, and they tell him that he went to scout the road. This appears to satisfy the cardinal and he tells the remaining musketeers that it is time to leave. Porthos and Aramis get up and join the cardinal as he departs.
Porthos and Aramis lie to the cardinal without blinking, but because their lie is reasonable enough, the cardinal assumes it is the truth. In reality, it is not clear to anyone, including Porthos and Aramis, what Athos plans to do.
As the cardinal, Porthos, and Aramis ride away from the inn, Athos makes his way back to it. He tells the cardinal’s guards who are standing watch that he has a message to deliver to Milady from the cardinal. The guards allow Athos to proceed, and he makes his way to Milady’s room. When Athos enters the room, he locks the door so Milady cannot escape. Milady is shocked to see Athos because she thought he was dead. Milady refers to Athos as Count de La Fère when addressing him and he refers to her as Anne de Breuil.
This passage is a major moment in the narrative, as it is the first time that Athos is reunited with his former wife. It is never made clear how Milady is still alive after her trip to the woods with Athos, but that is of little importance. What matters is that both Athos and Milady know scandalous details about one another’s past, and this is the first time where they are meeting face to face in many years.
Athos tells Milady that he knows all about what she’s been up to since allying herself with the cardinal, including her relationship with D’Artagnan. Athos also tells her that if she tries to kill D’Artagnan, then he will kill her. This threat doesn’t seem to register; Milady responds by saying that she will kill D’Artagnan “after she has died.” Milady doesn’t specify who “she” is. This enrages Athos, who pulls out his pistol and points it directly at Milady’s face. He then forces her to give him the letter that the cardinal wrote on her behalf, which she is meant to use to deal with the Duke of Buckingham.
Presumably, the “she” Milady refers to is Madame Bonacieux, although it is not clear whether Athos knows this. Athos’s rage is sparked by Milady’s defiance, which he finds infuriating. It seems likely that there was more to their marriage that Athos never disclosed to d’Artagnan, and that the reader never finds out. Although he would like to rid himself of Milady once and for all, Athos acts with his brain rather than his emotions and dooms Milady’s mission by stealing her letter from the cardinal.
Having obtained the letter, Athos leaves and makes his way back to his companions who are with the cardinal. The cardinal thanks the three of them for their service and then departs. After, Athos tells his friends that he got ahold of the letter. Meanwhile, Milady makes her way to the ship that will take her to England. Although she no longer possesses the cardinal’s letter, she still thinks she can handle the duke. She knows that she cannot tell the cardinal about what happened with Athos because if she does, Athos will tell the cardinal about her brand.
Athos now possesses a letter from the cardinal, which essentially gives its owner carte blanche. Unfortunately for d’Artagnan and his friends, Athos’s victory is far from the last nail in the coffin for Milady. If anything, Milady is more determined than ever to succeed.