Elena was supposed to study medicine. Instead, at seventeen, she buried her adoptive father, Lucien, and watched the Holy Light Church take her adoptive mother, Elowen. It takes her two years to follow Elowen’s trail to Obsidian City. At the gate, her travel pass is revoked. By nightfall, Elena is Blood Slave 731. If she survives her first blood drawing, she gets another month. Then her blood hits the glass vial, and every light in the North Tower goes out, and Cassian—the Obsidian Prince who has not failed in three hundred years—looks afraid. The Eternal Night Empire feeds on humans and governs by bloodline. Its thirteen Clans now want a girl the records say died nineteen years ago. Cassian will not hand Elena over. She might find that comforting if his name were not on the order to hunt her down. As Elena searches for Elowen, a blood pact ties her life to Cassian’s. She needs his help, even after she learns what he did. Meanwhile, blood hunters close in, the royal court turns on itself, and something beneath Obsidian City begins to wake. Elena’s imprisoned mother is keeping a secret. Her father has returned with one of his own. Everyone seems to know what Elena’s blood is worth. No one will tell her what happened nineteen years ago—or what wearing the crown will cost.