As a witch, widow Stella Ochoa makes her living at the soul grinding job of spelling coal dust out of the air. But infrequently, she and her team of Hellfighters are called on to do the dangerous task of capturing an escaped demon. Now, years after demons have been put to use as power in steam engines, they are getting loose at an alarming rate. Each one kills and causes massive destruction of property. For King, God, and country, Stella investigates the increase only to unravel a plot only humans themselves could devise.