The brilliant but dissipated Sidney Carton first sees the paragon of Victorian heroines, Lucie Manette, in the courtroom where Charles Darnay is on trial for treason. Carton is so taken with her distraught and delicate appearance that he revives his sluggish soul and rescues the object of her feminine attentions: he raises doubt about the certainty of Darnay's being the actual perpetrator of the crime because of his strong resemblance to Carton, as well as by discrediting the witnesses, Basard, a spy, and Cly, his friend.
Following the trial, Carton takes Darnay to a tavern where Darnay may dine. After Darnay departs, Carton derides himself sarcastically for the unfortunate changes he has made in himself and for his reasons for inviting Darnay to join him:
(1) A good reason for taking to a man that he shows you what you have fallen away and what you might have been!
This is the first step in self-improvement: the recognition of where he is in his life. In Chapter 5 of Book II, as he drinks Carton reflects that Lucie is "a golden-haired doll." Then, looks across a terrace and
(2)...saw for a moment, lying in the wilderness before him, a mirage of honourable ambition, self-denial and perseverance.
After this, Carton stops by the home of Dr. Manette on Sudays as there are also other gentlemen callers. Lucie tells Mr. Darnay that sometimes on Sundays she has sat quietly alone and hears in their cul-de-sac in Soho, "... the echoes of all the footsteps, hurried and insistent footsteps that are coming by-and-by into our lives." Carton senses this, as well and remarks that there is a crowd that will bear down upon them.
In Chapter 13 of Book II, Sydney has a private conversation with Lucie in which he tells her that it is too late for him to change his life; however, he asks her to listen to what he is about to say. Against his despair, Lucie assures him that he may still be "much worthier of yourself" and she beseeches him to allow her to help him. But, Sidney replies that in his "degradation" he has had "old shadows stirred" and he acknowledges that Lucie has roused in him the "utmost good" of which he is capable. He vows to Lucie,
(3) "For you, and for any dear to you, I would do anything. If my career were of that better kind that there was any opportunity or capacity of sacrifice in it, I would embrace any sacrifice for you and for those dear to you."
In Chapter 20 of Book II, Carton visits after Charles Darnay and Lucie are married, asking Darnay if he may be his friend; here the intent by Carton is to be able to still be near Lucie. But, he also indicates that he cares what happens to Darnay, as well:
(4) "I am speaking about our being friends."
In the next chapter (21), Sidney becomes a favorite of Lucie and Charles's children even though he visits rarely. With the perceptiveness of children, the little girl and boy recognize the underlying goodness in him and have "a strange sympathy with him." Sadly, the boy dies, but before he does, he expresses his love and respect for Carton as he tells his mother,
(5) "Kiss him for me!"
In Chapter 8 of Book III, Sidney Carton suddenly appears to the surprise of Miss Pross who has discovered her brother Solomon while shopping, accompanied by Jerry Cruncher, who recognizes him as a spy-witness at the Bailey. Suddenly, a voice says, "Barsad." It is Sidney, who has talked to Mr. Lorry and arrived in Paris to see what aid he can give, now true to his earlier promise. For, Carton is aware that Barsad/Solomon is a spy who works as a turnkey at the Conciergerie. He takes Barsad into a room as he tells him,
(6) "...let us have one final word alone." [Carton has a plan to save Lucie's husband, Charles, who is imprisoned there because he is an Evremonde]
In Chapter 9 of Book III, Sidney talks to Mr. Lorry and informs him that if things go badly for Charles at his second trial, Sidney will gain access into the prison. But, Lorry surmises that access will not save the life of Charles. Sidney's observation causes surprise in Lorry, who "had never seen the better side of him":
(7)"You are a good man and a true friend...I could not respect your sorrow more, if you were my father. You are free from that misfortune, however."
Further in the chapter, Carton asks Mr. Lorry,
(8) "If you could say with truth, to your own solitary heart, to-night, 'I have secured to myself the love and attachment, the gratitude or respect of no human creature; I have won myself a tender place in no regard; I have done nothing good or serviceable to be remembered by' your twenty-eight years would be seventy-eight heavy curses; would they not?"
Lorry responds "Yes." Thus, to Mr. Lorry, it is apparent that Sidney contemplates some selfless act. Later, in Chapter Chapter 12 of Volume III, Sidney pretends to knock over Dr. Manette's coat, and stoops to pick it up when Manette's small case falls from it. Inside are papers for Mr. Lorry, Lucie and the children and others to leave Paris--papers that Carton has slipped into the case. There is also a certificate for Carton, and he asks Mr. Lorry,
(9) Promise me solemnly, that nothing will influence you to alter the course on which we now stand pledged to one another."
Carton's selfless plan is to replace Darnay in the prison cell and send Charles out as himself with the transportation papers.
In Chapter 13 of Book III, "the doomed of the day" await their fate and are carried to the guillotine in the tumbrils. Carton, who has drugged Charles, has switched places with Darnay and has Barsad remove him to the outside as part of their deal, now rides with the little seamstress whom he has tried to comfort.
(10) Carton: My poor child. It isn't understanding we need now. It's courage.
Seamstress: You're going to die in his place. Why?
Carton: He is my friend.
Seamstress: You're so brave... When we go to the guillotine, will you let me hold your hand? That might give me courage, too.
Carton: Yes. I'll hold it to the last.
Seamstress: To the last.
As the sacrificial victim for the husband of the woman to whom he has pledged himself, Sidney Carton is redeemed. As he mounts to the guillotine, the words of Jesus echo in his mind,
(11) "I am the Resurrection and the Life, ... he that believeth in me, though he were dead, yet shall he live: and whosoever liveth and believeth in me, shall never die."