Lucie shows compassion for Sydney Carton by allowing him to come by her house and be a family friend even though he is pining for her.
The love story of Sydney Carton and Lucie Manette is a love story for the ages. It was also completely one-sided. Carton knew that Lucie did not and could not love him. In fact, he also knew that she loved another—Charles “Darnay” St. Evremonde. Lucie was compassionate and had a good heart. She saw through Sydney Carton’s façade of drunken irreverence to see a man in pain.
Carton was no doubt in a great deal of pain even before he met Lucie. Feeling his life was being wasted, he drank it away and put very little effort into it. He accompanied Stryver and allowed the other lawyer to take credit for his brilliance. Sydney Carton did not care about credit.
During Darnay’s trial, Carton used a legal trick to create reasonable doubt in the jury. Darnay was acquitted. From that point on, Carton became somewhat of a fixture in the Manette household, even as Lucie was falling in love with Charles. Carton was aware of this, and content to pine at a distance. Despite both his drunkenness and his brilliance, it seems Carton was shy—at least when it came to Lucie.
Carton finally got up the nerve to approach Lucie, and he was honest with her. In a very romantic but egotistical way, he told her that he loved her, but that he knew he couldn't have her. He didn't want to. All he wanted was to be in her life, and be of some service to her. He told her that she had saved his life. He lived for her now.
"Since it is my misfortune, Mr. Carton, to have made you more unhappy than you were before you knew me—"
"Don't say that, Miss Manette, for you would have reclaimed me, if anything could. You will not be the cause of my becoming worse." (Book 2, Chapter 13)
Lucie treated Carton with great respect during this conversation. She was sweet to him, and almost reverent, as she realized that he was willing to sacrifice everything for her. All he asked was to be in her life in this small way. His remarks were prophetic.
"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. Try to hold me in your mind, at some quiet times, as ardent and sincere in this one thing." (Book 2, Chapter 13)
In the end, Carton made good on his promise. He was allowed to accompany the Manettes to Paris, and there he did what he could. He traded places with Charles, and died at the guillotine so that Lucie could be happy. It was his last romantic gesture.