Boy is there ever initial wretchedness. The Marshalsea prison is the most depressing place on earth, with no sunlight, laughter, or anything else that might lighten the life of unhappy Amy, who slaves each and every day to take care of her family.
When Amy meets Arthur, everything suddenly seems to improve. He's the first person to take any interest in her, and she quickly falls in love with him. Just like that, the mood lightens, as Amy is hired to do some sewing work, gets a slightly different take on life outside the prison walls, and begins to have some mild aspirations separate from what her father wants.
It's funny – in this rags to riches story it's actually the riches that turn out to be the problem. Dorrit inherits a huge pile of money and immediately makes his family cut off ties with anyone they ever knew and relocate to Italy. Amy is no longer with Arthur and can't even communicate with him. (Although she can write him letters and send them off on the sly, he can't write to her because she has nowhere secret to receive mail.)
What finally frees Amy is the second wave of poverty, as all the money Dorrit had goes up in smoke in the Merdle fiasco. What's different this time is that it's Arthur who's now in jail and needs her help. So instead of feeling like loving her would be taking advantage of her gratitude, Arthur knows they are on an equal footing now. The final ordeal, though, comes in the form of Mrs. Clennam's giant secret: she is not Arthur's real mother after all, and she has held back a will that would have made Amy very wealthy. What should be done with this earthshaking information?
Apparently nothing at all. Amy is rewarded for growing up and separating from her father by getting Arthur – but yet again, she is the caretaker in the relationship. She decides to eventually tell Arthur the truth about his family, but she burns the will and thus forgoes her own inheritance. So, in this story, rags are rags, but riches are not money, but companionate love. Aw.