I am still unclear as to why the library door was unlocked when everyone went to check. If the booby-trap was set before Harry_T went in there and was locked in, why unlock it? I am guessing the poster who suggested that the internal keys were the same and this is how Poohbear_nc unlocked it, just not clear on why.
In fact, this was one of the things that may me afraid I had chosen the wrong person. I guessed right, but I was still second guessing myself.
May the sequel have gravy...