Outside the city, a woman named Emilie claims herself to be a prophet and orders the people of France to March on Spain. Her visions have told her that King Philip is the devil.

The Musketeers visit her came and tell her to disband her army, but she refuses. They think she is mad, but Aramis urges them not to dismiss her as a religious nut. Treville orders him to infiltrate Emilie's camp and learn what she is planning.

Back at the palace, Louis has made Milady his mistress, giving her rooms and gifts, but she has trouble keeping her true identity a secret from him.

Perales worries Rochefort is delusional about Queen Anne, so he orders Rochefort's favorite prostitute to murder him. Rochefort kills her and blackmails Milady into killing Perales.

Aramis tells Emilie that he has deserted the Musketeers to join her cause, and she welcomes him with open arms. Emilie's mother is skeptical. 

Queen Anne grows jealous of Milady's influence over Louis, so she decides to visit Emilie to beg her to disband her army. Constance goes with her for protection, but the two of them end up being taken prisoner. After Constance drinks the soup intended for Emilie, Aramis realizes that Emilie's mother has been drugging her to cause the hallucinations she mistakes for visions.

When Louis hears that Perales is dead, Rochefort pins the murder on Emilie. The King orders the Musketeers to bring her in for questioning. Emilie thinks she is being invited as a guest, so she agrees to go alone. 

Athos helps Emilie through the withdrawal symptoms, and a few days later she also realizes that her visions were fake. She returns to her camp and disbands her army.

After yet another disappointment, Louis decides that he needs to take action with the Musketeers, so he removes Treville from his post as their commander.