Welp, this looks like the fastest I'll drop reading a series...
As usual for this kind of story, the duke is going to be the love interest, isn't he? Except he wanted to kill two innocent children and killed their innocent teacher for not letting him do it, and probably any other servants that were in the marquis' house. No thanks.
And anyways, she talks about "saving those children" by preventing the marquis from turning crooked, but they were illegitimate, so if he lives a righteous life, they shouldn't be born at all.