Quote 1
She was the golden thread that united him to a Past beyond his misery, and to a Present beyond his misery: and the sound of her voice, the light of her face, the touch of her hand, had a strong beneficial influence with him almost always. (2.4.3)
Lucie becomes a conduit for Doctor Manette’s own experiences. Deprived of his life in prison, he begins to live through her.
Quote 2
"Charles Darnay, mysteries arise out of close love, as well as out of wide division; in the former case, they are subtle and delicate, and difficult to penetrate. My daughter Lucie is, in this one respect, such a mystery to me; I can make no guess at the state of her heart." (2.10.59)
Doctor Manette emphasizes the distance that can exist between even the closest of family members—a theme that the narrator himself later explores.
Quote 3
The faintness of the voice was pitiable and dreadful. […] Its deplorable peculiarity was, that it was the faintness of solitude and disuse. It was like the last feeble echo of a sound made long and long ago. (1.6.6)
Doctor Manette’s time in prison has robbed him not just of time but of his ability to re-enter the world, as well. Even his voice seems to have been forgotten.