Who is Detective Ezrael Carver from The Haunting of Alaizabel Cray and what is their importance?

Detective Ezrael Carver shares an office with Inspector Maycraft. Carver is neither tall nor short. He has black hair, a thick black moustache, and his clothes are always impeccable.

Detective Carver maintains a map with push-pins, diagramming the murders of Stitch-face. Some of the murders, however, are marked on the map with green tacks, because Carver believes they are the work of someone else. His partner, Inspector Maycraft, rejects this theory.