1897 London, a final showdown is about to begin  

London's underworld is no place for a young woman, even one who is strong, smart and part-automaton like Mila. But when master criminal Jack Dandy inadvertently breaks her heart, she takes off, determined to find an independent life, one entirely her own. Her search takes her to the spangled shadows of the West End's most dazzling circus. 

Meanwhile, taken captive in the Aether, Griffin King is trapped in an inescapable prison, and at the mercy of his archenemy, The Machinist. If he breaks under the hellish torment, The Machinist will claim his powers and control of the Aether itself, and no one in either world will be safe—especially not Finley Jayne and her misfit band of friends.  

Finley plunges headlong into the Aether the only way she knows how, by temporarily dying. But she cannot parry The Machinist's maneuvers for long. To defeat him for good, Griffin will have to confront his greatest fear and finally come face-to-face with the destructive power he wields.