No, the character I started with in my imaginings a couple years ago isn't the antagonist (I don't think). But my antagonist has a...let's call her a victim of sorts, I suppose. My jaw dropped today when I realized this victim could VERY easily be a slightly revised version of that character I had intended to put in this (now-changed) story. Which means that I could write a companion story where her story gets told after all.
Well, I think it's interesting, anyway.