Both Lucie Manette and Madame Defarge of A Tale of Two Cities are flat characters; that is, they do not change throughout the narrative. Lucie is the stereotypical Victorian heroine who swoons when she feels a little ill. She is the idyllic heroine, virtuous and devoted to her husband and father. Throughout the novel, Lucie acts as the "golden thread" that keeps Dr. Manette functional and ties Sydney Carton to her as well as her devoted husband, Charles Darnay. Thus, Lucie is a catalyst for other characters inspiring, for instance, Sydney Carton to emerge from his dissipation to heroism. With her name meaning "light," Lucie supplies the impetus to resist the darkness of the revolution represented by Therese Defarge.
While Lucie Manette functions as a flat character who acts as a catalyst for others, Therese Defarge, also a flat character, acts as symbol of the evils brought forth by the revolution. As a result of the tragedy involving her family who become victims of the aristocracy, Mme. Defarge vows vengenance against the Fremch nobility, particularly the Everemondes of whom Charles Darnay is part. A killing machine, Madame Defarge makes no distinction between the grandson of one of the brothers who molested her sister; she feels no guilt for the Everemondes and expects no forgiveness from others. Charged by the revolution for which she has waited, Madame Defarge delights in the bloodlust, but Lucie Darnay is terrified by it.