I have two characters that could end up getting involved. Caelestis would feel obligated to investigate since he's part of the Rangers (and he often pokes his nose in on serious matters regardless), meanwhile Cipher is a [now cranky] demon who might be interested in finding the killer out of pure intrigue. Cipher's morality is questionable so he could go anywhere from aiding the cause solely out of his own curiosity, to offering Cassian shelter, or even leave red herrings to make the detectives' lives harder. I could throw either (or both with restrictions) in on this.