Sinners' Kingdom. Nic Ward, #8

Criminal underworld meets literal underworld. The mayor may think he runs things in Jarvis, but the rest of us know better. Vincent Dean's criminal empire controls the illicit trade that is the lifeblood of the city. And Ruby McGinniss, however adeptly she plays the part of his empty-headed trophy wife, controls Vincent Dean. As someone who's made a career out of helping the little guy get justice, I'd happily watch their corrupt empire burn.
But now they've made a demon mad, and I'm the only one in town with the know-how to save them. Which would be too bad for them-if they were the only ones in danger. The thing is, they've got a little girl whose only crime is being born to the wrong parents, and she's in Hell's crosshairs too. Let an innocent child die, or help her parents keep on getting away with literal murder? Put it this way-it won't be the first time I've fought for the bad guys.
And hey, at least Dean and McGinniss are the devils I know. So long as they don't have any tricks up their sleeves.