You have to be careful with games like that. There's nothing worse than having a wonderful game, then finding out later that one of the players was freaked by it but didn't say anything because he/she didn't want to ruin things for other people.
Having a game in the modern era means you can tackle modern, relevant story lines - and somehow the "get the teenager off the streets and away from her pimp" type plot will work with players whose PCs always hit the brothels in the fantasy worlds.
Butcher doesn't usually deal with things like that, but a few other authors have. A very few - it takes effort and skill to work that type of thing into a plot and make it work. Lackey did some urban fantasy a few years ago where the Seelie wanted to help children and the Unseelie sold B&D kiddy porn (with spells on it so if you tried to copy the VHS tape it would self destruct). The good elves would try to save kids and not all of them would get saved... If memory serves she had 3-4 books in the Serrated Edge series which overlapped with some of her other modern fantasy novels.
I could easily see a plot based around a changeling or scion whose mystic parent was a negative sort. A sort of "Help? I didn't eat your mother - what more do you want" type thing. Maybe a Yellowbeard with his "No woman ever slept with me and lived" vibe going on.
But again, make sure everyone at the table is up for a theme like that.
Richard