What a wonderful story! The characterizations were spot-on, as were Filch's observations. His point of view is very believable and sympathetic, but not over-done (thinking of his description of his background and comments like the ones about Mrs Norris). Love the little details, from how long it took Dumbledore to use his first name, to what a bad sign it was when Snape's voice became smooth, to being uncomfortable with all the cat pictures in Umbridge's office.