Linda doesn’t fully understand the horrors of slavery. She knows that her role is to serve white people, but doesn't really understand what that means. But she's a smart girl, and she starts noticing things. Things like, her new masters, the Flints, are really cruel to her brother William. And the difference between the way her mistress is dressed and the raggedy clothes that she's forced to wear. Or the way Mrs. Flint can't lift a finger around the house but has no trouble watching a slave whipped until she bleeds.
So, yeah. Linda starts getting a pretty good picture of the "monster" that is slavery.
Linda takes a lover, Mr. Sands, hoping that it'll get the lascivious Dr. Flint off her back. Not so much. In fact, Mr. Flint ends up enslaving Linda in an entirely different way. Once her children are born, she can't exactly leave them behind while she goes gallivanting off to seek freedom.
It doesn't get much more nightmarish than this. Linda hides herself away in her grandmother's teeny garret, but it's not the romantic kind. Mice and rats crawl on her, ants bite her, she freezes in the winter, and soaks in the summer. Oh, also, she can't sit or stand, because the ceiling is too low. The one bright point? She can peep out at her children and overhear conversations on the street.
Seven years later, Linda leaves her awfully grave-like crawlspace and goes North. She scores a job as a nursemaid for the British-born Mrs. Bruce who is super nice and helps Linda out a lot. Even though Dr. Flint is still pursuing her, a network of friends and family keeps her safe.
And then Dr. Flint dies. Hooray! Sure, now his daughter technically owns Linda, but the second Mrs. Bruce manages to buy her. Linda and her children are finally free.