Necessary Cruelty

Chicago is a city of ghosts and tough detectives. Here, beneath the guise of ordinary people, live fairy changelings that no one believes in anymore. This is where the iconic Route 66 begins. And even the river bearing the city's... name flows in a direction opposite to the natural flow.
A minor detail of the fantastical urban puzzle is a small detective agency called "Sweeney Private Investigations," whose owner, Loreyna Sweeney, fearing being labeled insane, hides her medium gift and kinship with fairies from people. The agency's daily routine includes spying on unfaithful spouses and other mundane matters. However, there are also more complicated investigations...
A fairy girl dies under strange circumstances - is it an accidental murder, as the police believe? Or is someone hunting the non-humans of Chicago? But there are gaps in the victim's schedule: what was she doing for several hours each week? What secrets did she have, and are they connected to her death?
Loreyna and her partner - former police officer Edward Carter - will have to rule out numerous theories before they get to the truth.
Meanwhile, a maniac (or an imitator?) is on the loose in the city - the "killer from the gas station," and by coincidence, the detectives take on that case as well.
"On the other side" of Chicago - in the Ghost World, things are also restless...
All of this is in the second book of the "Sweeney Private Investigations" series.