Red Iron Nights (Garrett, P. I. Series #6)

Blood-soaked blades have been taking their toll among the luscious lovelies in Garrett’s home city of TunFaire. And though Garrett can be as civic-minded as the next guy—unless the next guy is Captain Block of the Watch—the private eye isn’t sure he really wants to take on a serial killer psycho who does too good a carving job and never leaves any of the blood behind.
 
Still, having Block pay him for his services with lots of ill-gotten government funds, and having his own partner, the Dead Man, strenuously urge him to take the case, prove an irresistible combination for Garrett. And so he begins a search that would take him from the lowest slums to the highest estates, from confrontations with magic-spitting enemies to run-ins with the king of crime’s wayward daughter, to a final encounter with an ancient evil that has once again been loosed on his unsuspecting town.