The French king is overjoyed to learn that Buckingham is dead; in addition, he is finally able to return to the siege. On the way, he and the musketeers stop at an inn where "the man from Meung" appears and tells d'Artagnan that he is under arrest. He identifies himself as Count de Rochefort, Cardinal Richelieu's agent. D'Artagnan's three comrades will not allow him to be arrested; they promise to deliver him to the cardinal at the appointed time.
Later, the cardinal tells d'Artagnan that he is accused of conspiring with enemies of France, intercepting state secrets, and attempting to thwart his general's plans. D'Artagnan defies the cardinal to name his accuser. He states that his accuser is a woman branded by French justice, a bigamist who poisoned her second husband, tried to poison d'Artagnan, poisoned Constance Bonacieux, and was guilty of many other crimes.
When d'Artagnan finishes the tangled story of Milady's web of crimes, including her being sentenced to death, a shudder runs through the cardinal's body. Still, though, he thinks that d'Artagnan should be tried. It is then that d'Artagnan shows the cardinal the carte blanche "paper of protection" which the cardinal himself gave to the wicked Milady, stating, "The bearer of this letter has acted under my orders and for the good of the State. Richelieu."
The cardinal pauses, sits and writes. D'Artagnan wonders if it is his death sentence. It is not. The cardinal has written out a commission for "someone" to serve as a first lieutenant in the musketeers; d'Artagnan can fill in any name he chooses. The cardinal reminds d'Artagnan, however, that the opportunity is given to him. d'Artagnan first offers the commission to Athos, but Athos refuses it because he has inherited some money. Then Porthos turns it down because his mistress has inherited a fortune. Aramis refuses it because he is finally entering a monastery. Thus, d'Artagnan has to accept the commission. The novel ends with d'Artagnan's fighting three duels with Count de Rochefort. Then Cardinal Richelieu orders them to become friends. To seal the friendship, Count de Rochefort makes Planchet a sergeant in the guards.
After only a short time in Paris, our young Gascon has evolved, as did Monsieur de Treville, from being a country boy to being a power to be reckoned with in the King's Musketeers. He is now a friend of the cardinal and also a defender of the queen. The other musketeers are happy and living their own individual lives. Here, as in most nineteenth-century novels, all's well that ends well.