The Agent's Demon - Locke & Steel, #1

IT TAKES A DEMON TO CATCH A DEMON LONDON, 1888When her mentor is brutally murdered, Hazel Locke is dragged into the investigation as the newest agent at Her Majesty's Paranormal Investigation Agency. To solve the case, she must summon a demon partner called a Hound, a creature who can track down others of its kind. But the demon she summons is unlike any she's encountered before, and he wants nothing to do with her or the Agency.
As the body count rises, Hazel realizes there's more at stake than getting justice for her mentor. A ruthless killer haunts the streets of London, and to stop them, she and her demon will have to put their differences aside and work together to solve the crime - no matter where the journey takes her... The Agent's Demon is the first book in the historical paranormal series, Locke & Steel.