Dickens' plot becomes even more cohesive with the discovery of Madame Defarge's connection to the Evrémonde family. With her disclosure, she reveals the last major secret of the book, and the reason for her ruthless hatred of Darnay and all aristocrats becomes clear.
Madame Defarge has stood apart from the other revolutionaries in her attitude and purpose. For instance, rather than being swept up in the revolutionary fervor of a mob, she incites and controls it for her own objectives, as in the case of Foulon's death. Similarly, rather than viewing the Revolution as an agent of positive change, as her husband does, Madame Defarge regards it as an instrument of vengeance and retribution. Readers now understand that her cold-blooded rage is the product of a devastating childhood trauma. In killing her family, the Evrémonde brothers killed her heart. They also, in effect, killed their own future, for Madame Defarge seems intent upon wiping out the entire Evrémonde line, including Darnay's innocent wife and daughter.
Dickens uses the relationship between the Evrémonde brothers and Madame Defarge to represent the relationship between the French aristocracy and the lower classes. As he states repeatedly throughout the book, the horrors of the French Revolution grew out of the horrors of the old regime, just as Madame Defarge's viciousness stems from the ruthlessness of Darnay's father and uncle.
