Tanzy Hightower has crossed the veil and entered the Unseen world to fulfill the destiny she has at last embraced, to either seal or destroy the veil between the Seen and Unseen worlds. She is the only mortal in a land teeming with creatures who want her dead. To stay alive long enough to stop Asher, the most powerful of the Unseen, Tanzy accepts his marriage proposal and seeks refuge inside his palace. On the Seen side of the veil, Tanzy's allies are fragmented and lost, without leadership. They must gather forces and train an army of candidates to defend their world against unfathomable predators poised to strike should the veil holding them at bay dissolve. While Tanzy has accepted her own inevitable death in fulfilling her destiny, her closest friends refuse to stop searching for the impossible: a way to save Tanzy's life.