Constance heads to her execution, but D'Artagnan, Treville, and Athos rescue her, turning on Rochefort.
Porthos meets with Vargas and tries to get him to turn on Rochefort.
The Musketeers come up with a plan to free Aramis using Milady's help. Elsewhere, Anne begs Louis to believe her innocenve, but Rochefort reveals to him that she was having an affair with Aramis.
Rochefort visits Aramis and offers him a deal: confess to having an affair with the Queen, and the King will allow her and her child to live out their lives in exile. Instead, he testifies that Rochefort is a Spanish spy.
Marguerite testifies against Aramis and the Queen in court.
The Musketeers show up to help Porthos capture Vargas.
Back at the palace, Marguerite kills herself and leaves a note confessing everything. Rochefort finds it, and tears it up. He offers to help Anne escape punishment, but she rejects him again.
In retaliation, he tells her that Aramis will be tortured. Milady rescues Aramis before that can happen.
Milady confesses that she is tired of a life of crime and killing. She tells Athos that she is leaving for England, and she will wait for him until sundown to come stop her.
Rochefort urges the King to sentence the Queen to death, and he reluctantly signs the warrant.
The Musketeers bring Vargas to the palace, and they realize that Rochefort plans to kill Anne. Aramis rushes to her side to save her. He wounds Rochefort, and D'Artagnan kills him in a duel.
Louis releases Anne, clearing her of all charges, and he decides to go to war with Spain. Aramis tells the others that he is resigning his commission, and he will live as a monk instead.
Constance and D'Artagnan get married in a small ceremony. Athos heads to meet Milady, but Treville appoints him as head of the Musketeers, keeping him in Paris. Milady leaves for England, heartbroken.
Knowing war is coming, D'Artagnan, Porthos, and Athos ride to bring Aramis back to fight with them.