In this sequel to the New York Times bestselling, "pulse-pounding" (Publishers Weekly) A Door in the Dark, Ren's intellect and cunning are stretched to the limit in her quest to take down the system that stole her father's life.

Ren Monroe is one step closer to avenging her father's death. Bonding with Theo Brood has allowed her to infiltrate one of the oldest houses in Kathor. But Theo's father is playing his own game. He exiles Theo, isolating Ren in an attempt to break the unwelcome grasp she has on his son. Ren might possess more resources than she ever imagined growing up, but her plans of revenge will vanish without allies.

Enter House Tin Vori.

Years ago, the Broods led an unprecedented raid to destroy one of the other ancient houses. Their only mistake was not finishing the job. A few of the Tin Vori siblings survived, and they haven't forgotten the crimes committed against their family that fateful night. Quietly, they've plotted their own revenge, waiting for just the right moment to strike. And Ren Monroe might be their best chance.

Like fire, the Tin'Vori siblings are as dangerous as they are useful, both gifted in rare magics. Ren must decide how to unleash them against House Brood without hurting Theo in the process. Her feelings for Theo are growing past the boundaries of their bond, and Ren finds herself balanced on a knife's edge, a breath away from immense power or utter ruin.