Harry Potter (books)
the purrisoner of catskaban
by Duskglass
in which there's both a convicted mass murderer and a surprisingly cat-friendly dog on the loose at Hogwarts, the school's resident feline population and most recent Defence Professor are both behaving rather strangely, and Minerva McGonagall may or may not have accidentally joined a cult.((or: local professor listens to the secret whispers of cats; somehow this changes everything))