Arcane Detective - Oleander's Irregulars, #1

Miller Watkins was an FBI agent until he met the Darkness face to face and failed. Now he works for Oleander fighting the Darkness, however he can, to protect the city he loves. With the help of some supernatural creatures, a couple of dream-sibyls, an invisible housekeeper and his own considerable powers, he solves the problems of the arcane community. Or tries his best. When a teenage girl goes missing, he must unravel a tangle of coincidences that dog his investigation at every step.
Something larger is at stake than a simple missing person, and he must solve that riddle before he can move forward. The ever-present Darkness is growing, and Miller must use every skill, strategy and artifact that he can come up with to keep it at bay......or die trying.