Feeling it necessary to separate Tellson's Bank from his own personal business, Mr. Lorry finds an apartment for Lucie and her family, and leaves Jerry Cruncher with them to act as guard. On the way back to Tellson's Mr. Lorry is stopped by Monsieur Defarge, who brings news that Charles is safe, a note for Lucie from Dr. Manette, and instructions for Lorry to let Defarge in to see Lucie.
Mr. Lorry keeps his two worlds as separate as possible, but is deeply committed to both. It is unclear if Defarge has tampered with this letter, but certainly at this moment he is acting as a secret agent for the Revolution.
On their way to the apartment, Mr. Lorry and Defarge are joined by Madame Defarge, who is knitting, and The Vengeance. Defarge tells Lorry that, in order to be able to protect Lucie, Madame Defarge must see and remember Lucie's face.
That Madame Defarge is knitting shows that she's planning to add Lucie's name to her list of victims. "Safety" and "security" are words the power-hungry use to mask their real intentions.
In the apartment, Lucie reads the note from Charles: he is fine, and under Dr. Manette's protection. She gratefully kisses one of Madame Defarge's hands, but Madame Defarge coldly withdraws to her knitting. Lucie pleads for Madame Defarge to help Charles, to use her influence as a "sister-woman." Madame responds that she has seen so many women suffering for imprisoned husbands that Lucie's predicament doesn't mean much. After they leave, Lucie tells Mr. Lorry that Madame Defarge seems to throw a shadow over all her hopes.
This crucial meeting between the two key female characters reveals a lot about each: Lucie has compassion even for this terrible woman and asks for her pity; Madame Defarge shows she is no "sister-woman" but is a cold messenger of death. Madame Defarge is meant to be a frightening perversion of femininity, while Lucie, with her goodness and compassion, is the model of it.