Anne tries to tell Louis what happened with Rochefort, but Rochefort has already set her up using the letter she wrote earlier in the season when she thought the king was dead.
Milady plots with Rochefort, but she changes her allegiance after he tries to strangle her.
Athos and Aramis reveals to Treville and the other Musketeers what happened between him and Anne. Porthos is particularly upset at the idea that Aramis is the dauphin's father.
At the palace, Rochefort tries to sway Louis to punish Anne for her "treason" but he won't make a move against her.
Catherine arrives in Paris, tracking Milady. She watches her meet with Athos, D'Artagnan, and Treville. They get her to betray that Rochefort is a Spanish agent. Milady promises to show them where Rochefort keeps his incriminating documents.
Aramis apologizes to Porthos, and Porthos tells him to deny ever having been involved with Anne to save her life.
Back with Louis, Rochefort orders Marguerite to poison the king. The Musketeers and Milady sneak Anne out of the palace to protect her.
Catherine confronts Milady, forcing her back into the noose she escaped. Athos saves her from hanging and reveals that they planned the whole thing to trick Catherine.
Marguerite tries to warn Louis about the poison, but Rochefort stops her.
In Rochefort's chambers, Milady and Athos hash out their past and seem to come to a tipping point. They are nearly caught, but Milady finds a secret compartment to hide them in. The close quarters result in a passionate kiss.
Aramis takes Anne back to the convent where they first fell in love, hoping to protect her there. The nuns offer her refuge.
The King succumbs to poison and Rochefort has Lemay arrested. He frames Constance and Lemay (and Anne by extension) for his attempted murder.
For his "treason", Lemay is executed while Constance watches.
Anne decides to return to Paris, despite the Musketeers' urgings to stay hidden. Marguerite leads Anne into a trap, and she is arrested by the Red Guard for the attempted assassination of the King.