What secret does Mme. Defarge tell Jacques Three and The Vengeance and how does this information clear up some of our questions? (From Book 3 Chapters 11-15)

Carton also learns that Madame Defarge was the sister whisked away to safety away from the Evermonde brothers by the brother who Dr. Manette saw die of a stab wound, so she has a strong personal vendetta against Darnay.