The Shadow Broker - Mr. Finn, #1

A private investigator must unravel a blackmail plot targeting a criminal information brokerage before the FBI and a hired killer stop him. A vigilante justice P. I. series.  Finn Harding specializes in finding people who don't want to be found. Bishop runs a black-market information brokerage on the dark web, selling stolen personal data to the highest bidder.  When someone blackmails Bishop, threatening to go public with his identity and crimes, he hires Finn to find the person behind the plot.
During his investigation, Finn draws the attention of the FBI's cybercrime unit investigating Bishop, a psychopathic hitman hired to take out the blackmailer, and a Detroit mob boss hellbent on taking over Bishop's operation.  As Finn gets closer to unraveling the mystery, he discovers his ex-wife and young daughter have become targets in the sinister conspiracy.  Can Finn survive long enough to unmask the blackmailer, save his family, and escape the FBI's and the mob's grasp?  The Shadow Broker is the first novel by award-winning author Trace Conger.
The novel won a Shamus Award from the P. I. Writers of America as one of the best crime books of the year.