Harthouse is doing really well as a politician. (He's smart, good-looking, willing to say whatever people want to hear – sounds about right.)
Meanwhile, he is sucking up more and more to Louisa with his talk about how generosity, benevolence, and all those other human emotions don't really matter and aren't real anyway. She is really a good audience for this – if everything is "hollow and worthless" then who cares that she threw her life away on this horrible marriage?
Bounderby rents a house in the country, away from Coketown. He loves to brag about how he grew up in the gutter and now lives in this luxurious house and is friends with a fancy gentleman like Harthouse.
Harthouse comes to visit often. One day, he has a long conversation with Louisa about her brother. It turns out that Tom is a gambler, has a lot of debts, and usually hits Louisa up for money to pay them. Harthouse offers to have a talk with Tom and put him on the straight and narrow path.
This is a huge coup, obviously, since he has basically become Louisa best – and only – friend and confidant. He follows up with a long, drawn out thing about how Tom needs to treat her better, implying that he himself would treat her very well – hint, hint.
Tom finds them in the garden. Louisa goes inside, and Harthouse sits Tom down to have a chat. Of course, he does this near a window so that Louisa will see him following through on his promise.
Harthouse offers Tom money for his debts, but Tom says he no longer needs it. At the same time, Tom complains that Louisa isn't doing her part with Bounderby. She isn't cajoling him and getting money out of him through feminine wiles like she should be (Tom is basically sad that his sister is proving to not be a very good prostitute. Nice.) Harthouse then gives Tom the money anyway, and makes Tom promise to be nicer to his sister.
At dinner, Tom throws a few kind words Louisa's way, which makes her smile happily. Harthouse is happy too, knowing that she will attribute her brother's behavior to the talk.