bonus Dresden Files theory of the night (because who needs sleep or to get homework done anyway):
From TvTropes, “John Marcone’s True Name is…John Marcone. Yes, in Even Hand he says that it isn’t really his birth name, but a birth name and a True Name aren’t necessarily one in the same—remember that a mortal’s True Name changes over time. The True Name isn’t what’s written on your birth certificate, it’s how you self identify, and in Even Hand, Marcone says he can barely be troubled to remember his birth name most of the time. He’s probably been going by John Marcone in public and private for so long that it now "counts” as his True Name.
So somewhere down the line, he’s going to have one hell of an Oh Crap moment when he realizes this precaution he’s taken has backfired. (Contrariwise, there is also the possibility of someone going to all the trouble of tracking down Marcone’s birth name, using that and having an Oh Crap moment because it didn’t work.)“
I say, why not have both Oh Crap moments? First, this week’s villain dramatically reveals the name she/he has tracked down, saying it just write…to absolutely no effect, and someone "distracts” (probably shoots) them before anything else can be said on the matter.
But Harry noticed that Marcone looked almost scared when the villain started saying that name, and surprised when nothing happened.
So at the end of the book, once whatever has forced them into the Enemy Mine situation has been dealt with, they’re about to go their separate ways when Harry turns around and calls out, “Marcone,” as if to say one last thing to the Baron of Chicago, and he says it with whatever just-right - or maybe just nearly-just-right - inflection and puts a little power into the word. And Marcone sort of freezes for a millisecond, or maybe shivers, and turns and looks him dead in the eyes and they both know, and know the other knows and know the other knows they know; but neither of them says another word, just turn and go their separate ways (until the next time.) (Marcone is so going to want Harry killed for this.)