Little Underworld by Chris Harding Thornton

Omaha, 1930. When ex-cop-turned-PI Jim Beely murders the man who assaulted his fourteen-year-old daughter, the last person he wants to see is local crooked cop Frank Tvrdik. Luckily, Frank isn't interested in the lifeless body in Jim's car. Frank has a proposition: he'll make the dead man disappear if Jim helps take down Elmer Kobb, who is vying for city commissioner and willing to backstab anyone who gets in his way.
Soon, Jim and Frank are sucked into a seedy world of crime and corruption, where no one is safe and nothing is what it seems. Then Jim is violently attacked and one of his operatives turns up dead within the span of twelve hours, and his search for the truth yields a web of lies and a mounting death toll. As he and Frank are pulled deeper into the city's dark underbelly and its absurd political machinations, Jim begins to question everything he knows about Omaha and his place in it.
In her moody, ferocious, and darkly funny follow-up to Pickard County Atlas, a novel Tana French called a "slow-burning beauty of a book," the native Nebraskan Chris Harding Thornton mines Omaha's sordid past, melding fact and fiction into an unforgettable tale of danger and deceit. Little Underworld asks: What does it mean to be good, and what is left for those of us who aren't?