This books, a Mary Balogh classic from 1991, is gripping, dark, and ultimately uplifting.
In the opening chapter, a man hires a young, sad looking woman outside Covent Garden and proceeds to have swift and rather brutal sex with her, realizing only after it's too late that she is a virgin. Afterward, he is haunted by the memory and sends his secretary to track her down. Upon his master's order, the secretary hires her to be a governess to the master's five-year-old daughter. It's hard to know what to think of this man, who turns out to be Adam Kent, the Duke of Ridgeway. We gradually learn, however, that he is a kind, caring, morally decent man married uphappily to a woman who loathes him and cares not a whit for their daughter.
Fleur, our heroine, does not realize who her benefactor is until after she's ensconced at the duke's country estate. Her reaction to him is one of loathing and fear, but gradually she learns to trust him and eventually to love him.
The story is sweet but filled with obstacles -- not just romance-novelly frivolous obstacles -- but serious problems. The ultimate HEA is so touching that I found myself puddling up, which almost never happens to me when reading HR.