After Athos sends the others to bed, he sends the four servants on four different roads to discover the whereabouts of Milady. Meanwhile, he goes for a walk and begins questioning some late wanderers. Each one of them is so frightened when they hear his question that they cannot speak; they can only point him in a certain direction. Finally, Athos finds an old beggar who is too frightened to accompany him but agrees to do so after Athos gives him a silver coin.
At the small house to which he has been directed, Athos is admitted by a tall, powerful man who shrinks in terror at Athos's request. However, when Athos shows him a piece of paper with the cardinal's signature and seal, the tall man recognizes the seal and agrees to accompany Athos.
Next day, after attending Constance's funeral, Athos investigates the garden and discovers Milady's footsteps. Shortly, Planchet returns with the news that Milady is staying at an inn and that the servants are keeping her under surveillance. That night, they prepare to leave, accompanied by the mysterious tall man, who is wearing a mask and a big red cloak.
Amidst a raging storm, they approach the inn and are led to a cottage, where Athos sees Milady. As she suddenly sees them, Athos breaks through a window, and d'Artagnan comes through the door. Then Porthos, Aramis, de Winter, and the man in the red cloak enter. Athos announces that Milady is to be tried for vile, innumerable crimes — in particular, for poisoning Constance Bonacieux, sending poisoned wine with the intent of killing d'Artagnan, and trying to coerce d'Artagnan to kill Count de Wardes. Then de Winter accuses Milady of corrupting John Felton, of being responsible for the deaths of Buckingham and Felton, and of being responsible for the mysterious death of his own brother — her husband, the first Lord de Winter. Athos then condemns her further because of her deceit in their marriage.
At this point, the executioner — the man in the red cloak — speaks; he reveals her origins and tells how she seduced his brother, a convent priest, to a life of crime. When the crime was discovered, he (as official executioner) had to brand his own brother. Milady escaped, he says, by seducing the jailer's son. She also helped the priest to escape. The executioner managed to track her down and brand her. He himself had to serve his missing brother's remaining prison term. Later, after Milady abandoned the priest for Athos (Count de La Fere), the priest surrendered, then hanged himself.
Athos asks each of the men for a verdict. Each one of them asks for the death penalty. Milady is carried to the edge of a river where she is tied hand and foot, and once again her crimes are recounted as she begs for her life. The executioner takes her across the river, and in the boat she frees her feet and tries to escape, but she cannot get up. The executioner cuts off her head, wraps her body and head in his cloak and dumps them in the river, crying out loudly, "God's justice be done."
These chapters bring to an end the horrible injustices of Milady Lady de Winter. As in most nineteenth-century novels, justice triumphs and evil is destroyed. But not before Dumas introduces one last mystery. In Chapter 64, he creates a wonderful sense of suspense when he has everyone who is quizzed by Athos quail before him, afraid to tell him where a certain person lives. As we discover later, Athos is looking for an executioner, and most simple and superstitious people fear such a man — even though he is only doing his job. It is poetic justice that Milady loses her life at the hands of an "official" executioner — especially since he suffered so terribly as a result of her evil conniving.
Moviemakers often revel in filming this final scene, where the climax of raging emotions and passions parallel the raging storm outside, suggesting the furious storms within the protagonists.
When the various men gather to denounce Milady's numerous and infamous sins, the list is truly impressive — a list that chills most people, but note that Milady feels that she is being treated unfairly. Even though she herself has just killed Constance Bonacieux, a young, innocent woman, Milady pleads that she herself is "too young" to die. Milady's death fits the crimes that she committed: her head, the source of all her conniving, is severed from her body and both pieces are thrown into the river. With her death, justice has been done, and the novel can now draw rapidly to an end.