You are one of my favourite authors, I have an LJ account as well and normally read your stuff on there or the quidditch pitch, but i have found lately after joining the snape_potter comm on Lj that I needed to join here as well.
I am really enjoying reading this, i found it a couple of weeks ago in my Lj inbox but it was chapter 2 and there is no point reading something part way through.
I can't wait to see what you and your co-author come up with in future chapters of this. I suspect that Harry does know who the vampire is which is also part of the reason that they won't show themselves to Harry.