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.

Odette Cosgrove’s father is Master Thomas Agardawes, head of the Alliance of Silver and Steam. She has grown up in the center of the Alliance of Silver and Steam; her childhood spent learning how to fight and take down the creatures. When her father asked her to head up a chapter of the Alliance in America she accepted. Love was waiting for her, but so were demons who knew she would be unready to handle them and they tore her new life apart sending her running back to London. Philippe Clemis is The Alliance of Silver and Steam’s best hunter. He’s killed hundreds of the vile demons and kills without remorse. When Odette shows up back in London after her family was slaughtered he’s assigned to get her reacquainted with guild ways - he’d rather be cleaning up the toilets. The obstinate female drives him crazy and makes him mad with desire because she challenges him in a way no one ever has. When a Kappa Demon attack on Philippe claims Odette instead the pair will have to work together to stop her transformation into the vampiric little demon. A journey across Europe and into hell itself to find a cure will force the pair to determine if what they feel is love or hate if they are going to make it back alive.