Harry Potter and The Serial Killer

A serial killer at Hogwarts! When panic and paranoia kicks in, what will Harry do? Oneshot, complete, no bashing, no pairings, no slash, intelligent Harry, winner of The Fan Fiction Creativity Award 0 times in a row, mentioned in Hannibal Lecter's Top 10 Serial Killers, mentioned in Agatha Christie's Top 10 Murder Mysteries, Order of Merlin (First Class).