Madame Defarge is one piece of work. If anyone has a right to be upset about the abuses that the aristocracy heaps upon the commoners, she’s the person. After all, her sister was raped by the Marquis St. Evrémonde. Her father died of grief. Her brother was killed trying to avenge his sister's honor. All in all, she didn’t have the happiest of childhoods. It’s completely understandable that she’d want to play a big part in the revolutionary attempts to overthrow the power of the aristocracy.
Of course, we don’t know any of Madame Defarge’s back-story until the very last twists and turns of the novel. By this time, we’re pretty accustomed to a description of her as the implacable wife of Ernest Defarge, the woman who never stops knitting. She runs a wine shop in Saint Antoine that just happens to be the hub of all revolutionary activity. The lifeline of the revolutionaries, Madame Defarge knits a pattern that becomes a record of all the people whom the revolution will destroy. It’s a rather dire task, but someone has to do it.
By the time we learn Madame Defarge’s history, then, we’ve already heard over and over again how "cold," "dreadful," and "frightfully grand" she has become. She may be smart, but she’s also ruthless. We’re not ever really given a chance to sympathize with her or to mourn the horrors of her past. When Dickens gets around to telling us about them, Madame Defarge has already turned into something of a monster. The meeting between Lucie and Madame Defarge makes this absolutely clear: Lucie falls on her knees, begging for mercy on behalf of her child. Madame Defarge stares at her coldly. She doesn’t even stop knitting.
Her problem, it seems, is that Madame Defarge just doesn’t know where to draw the line. As far as she’s concerned, "justice" for the fate of her family isn’t just that the Marquis gets murdered. Justice should, she thinks, include the "extermination" of all of the Marquis’ family. Given her druthers, Charles, Lucie, and even...