In the London Underground the Alliance of Silver and Steam is all that protects humans from demons. Felicia Ganon is no stranger to the demons that lurk in the night. After her parents were murdered in front of her the Alliance took her in and trained her. Vengeance became her only drive. Greyston Westham is more than just the devilishly handsome Captain of the Guard. He's an Incubus Demon who hunts his own kind because they have no use for lesser demons like himself. When a murderer is running lose that only the Alliance can deal with Felicia and Greyston are thrown together in a deadly game. Can she overcome her hatred of demons and give into the relationship that will save her life? Or will Felicia's hatred be her doom.

Eliza Kempe Dorley is always left in the background. As a female, being top inventor for the Alliance of Silver and Steam has as many draw backs as perks. She’s in charge of the creation of the many tools the Alliance uses in pursuit of the demons that run lose in the London Underground, which means without her, the demons would be harder to put down. It also means she misses all of the action and has never had the chance to really use any of her inventions. Lucius Cooley Willan is a Nightmare Demon with a penchant for gambling and sleeping with women he shouldn’t and its landed him in hot water. Now he spends his nights slinking in humans dreams and unleashing terrors so strong it kills them so he can capture their soul for his boss. But when he’s ordered to attack the group that hunts his kind he’s enthralled by the feisty inventor he comes upon. Eliza’s victim to Lucius in a way no others have been, a sensual dream that she can’t shake when she wakes up. When he bumps into her at the trains she’s an addiction he can’t shake. When he outright disobeys the demon who controls him for some out of dreams interactions with the Eliza, it will be up to him to save her from the nightmare he’s put her in.