With several hours to spare, Carton goes to the Defarge's wine shop with the purpose of making his face known to the revolutionaries. At the shop, he pretends to be unfamiliar with the French language and Madame Defarge closely examines his appearance. He overhears the Defarge's commenting on his likeness to Darnay and also overhears Monsieur Defarge meekly suggest to his wife that Lucie and her daughter's life should be spared in order to please the doctor who has suffered much in the cause of the revolution. Madame Defarge and her compatriots scoff at the idea and Madame reminds her husband that she is the younger daughter of the girl who died so horribly in the doctor's manuscript. Madame Defarge is without mercy and has sworn to wipe out the Evremonde race in its entirety. Carton returns to Mr. Lorry's apartment and waits for the doctor. When Doctor Manette returns soon after midnight it is not only apparent that Charles is doomed but that the Doctor's senses have become deranged. The doctor pitifully begs for his shoemaking tools. Before Mr. Lorry leaves to take the doctor to Lucie, Carton demands that the banker follow his instructions exactly. Mr. Lorry is to hold on to Carton's letters of transit and is to hold the similar papers of the doctor, Lucie and her daughter. He tells Mr. Lorry that Lucie and little Lucie are in grave danger and it is imperative that the family flees the city the next day before the transit papers can be rescinded. Mr. Lorry is to be ready to leave with the family at exactly 2pm the next day but he is not to depart until Carton has rejoined them after visiting Charles in his cell. That night Carton walks outside of Lucie's apartment for the last time.
That same night in prison Charles Darnay composes his mind and resolves himself to accept the death that certainly awaits him. He writes letters to Lucie, Doctor Manette and Mr. Lorry but never once thinks of Carton. Eventually he falls into an uneasy sleep and dreams of the happiness of their Soho home. He awakes and knows instantly that on that day, a day marked for 52 executions, he will die. As a church bell tolls the hours he counts each one that he will never see again until it tolls one o'clock and he hears footsteps approaching his cell. Sydney Carton enters and with quick dialogue and forceful appeals he convinces Darnay to change clothing with him one article at a time. Darnay believes that Carton wants to break him out of jail and knowing this to be impossible begs him not to perish in the attempt. Carton denies this plan and orders Darnay to begin writing as he dictates. As Darnay writes Carton prepares a chemical mixture and then forcibly applies it to Darnay, rendering the latter unconscious. Although Barsad fears that Carton will betray himself before the Guillotine falls, and endanger the spy as well, he yields to Carton's assurances and takes the still comatose Darnay out in his place. At two o'clock Carton is taken to a room where the other fifty-two victims wait. A young girl, a seamstress who knew Darnay from his prior imprisonment, approaches Carton, and after some dialogue in which she expresses her fears of death she realizes it is a different man. He motions for her to keep his secret and she implores him "O you will let me hold your brave hand, stranger?" He promises to do so until the last. The narrator looks forward in time and observes that the carriage bearing the still unconscious Darnay, his family and Mr. Lorry proceeds safely from the city and slowly but surely makes its way to the coast.
At the same time that Sydney Carton is awaiting execution in Darnay's place, Madame Defarge, the Vengeance and Jacques Three (the most bloodthirsty of the Jacques) hold a meeting in the woodsawyer's shed. Madame Defarge expresses her sadness that her husband lacks the resolve to see the Evremonde clan completely exterminated and she asserts that she must ensure that Evremonde's wife and daughter do not escape the Guillotine. Furthermore, Madame Defarge asserts that the doctor must also fall before the blade. To her compatriot's joy, Madame Defarge announces that she will go to the doctor's apartment and confront Lucie. She agrees to meet the others at the execution site before the blade falls. She carries with her a loaded pistol and a dagger. At the apartment Miss Pross and Jerry Cruncher are waiting to leave in a lighter carriage that will overtake and join the one that recently departed containing the family. They know that Carton has traded places with Darnay and that every moment counts. Jerry is so emotional that he proclaims to Miss Pross that he will never do "It" any more, (by which he means unearthing dead bodies) and that he will never again forbid Mrs. Cruncher from "flopping." Miss Pross understands neither of these allusions but passionately signifies that she has heard him. Miss Pross expresses her belief that it would be best if the second carriage did not depart from the apartment and raise suspicions. She sends Jerry to intercept their carriage and await her at a certain Cathedral door familiar to them both. After Jerry departs, Miss Pross is washing her face when she is surprised to see that Madame Defarge has entered the apartment. Madame Defarge demands to know the family's whereabouts. Miss Pross does not understand French and Madame Defarge speaks no English but the two women immediately understand that they are at cross-purposes. Madame Defarge inspects all the rooms but the one that Miss Pross blocks and the two women struggle and the pistol explodes and kills Madame Defarge. Miss Pross composes herself and then locks the apartment and flees. On her way to meet Jerry she drops the key in the river. When she meets Jerry he realizes that the poor woman has become deaf though he cannot understand why.
The tumbrels carrying those to be executed roll through the Paris streets. The doomed display varying countenances, from resolved to insane. John Barsad sees Sydney Carton holding the hand of a young girl and prays that he will not betray him. The Vengeance asks her friends in vain if they have seen Madame Defarge. As the Guillotine begins its work upon the fifty-two condemned to die, Sydney Carton and the seamstress hold hands and express their belief that God has sent them each other at this moment. They kiss each other's lips before they are parted. She is executed before him. Sydney Carton looks peaceful and sublime as he is led to the blade. Before he dies his thoughts are of the family that will live long and peacefully in England because of his sacrifice. He imagines that a son is born to them that is named for him and, as the blade falls, he says to himself, "It is a far, far better thing that I do, than I have ever done; it is a far, far better rest that I go to than I have ever known."
Analysis of Chapters 12-15
These chapters bring to the story to a close the story at the cost of two lives. Sydney Carton is able to fulfill his promise to give his life for Lucie's happiness by trading places with Darnay. Good, as personified by Miss Pross, triumphs over evil, personified by Madame Defarge when the latter dies by her own gun. Some critics have asserted that Carton's sacrifice is meant to be interpreted as a Christ-like act but others have insisted that because he dies for Lucie's happiness and not merely to save another his death is borne of selfish desires. In either case, Carton is depicted as having found true happiness in the moments before his death when he is able to bring comfort to the seamstress and assures her that like his own impending death hers will not be without purpose.