In an alternate history New York City—one hundred and fifty years after an earthquake from hell nearly destroyed the planet—the twenty-first century clings to an industrial age. Steam engines rule, and demon-powered technology is the up and coming thing. Henry Paine, a half-demon taxi driver, is the go-to guy for just the right demon to possess your machine and automate any mechanical gizmo with or without an engine. The creatures are tame as pets. Or at least they have been… until now. 

Wanda Snow is an exorcist who grudgingly admits to having a few drops of demon blood herself. She's come to New York to rid the city of demonic vermin as well as any other demons that get in her way. Wanda and Henry are naturally at odds, but the two are forced to become partners in a mutual goal to round up the rogue demons biting the Big Apple and take down the sinister tyrant who started it all.