Zachary Ezra Rawlins is a graduate student in Vermont when he discovers a mysterious book hidden in the stacks. As he turns the pages, entranced by tales of lovelorn prisoners, key collectors, and nameless acolytes, he reads something strange: a story from his own childhood.

Bewildered by this inexplicable book and desperate to make sense of how his own life came to be recorded, Zachary uncovers a series of clues—a bee, a key, and a sword—that lead him to a masquerade party in New York, to a secret club, and through a doorway to an ancient library hidden far below the surface of the earth. What Zachary finds in this curious place is more than just a buried home for books and their guardians—it is a place of lost cities and seas, lovers who pass notes under doors and across time, and of stories whispered by the dead.

Zachary learns of those who have sacrificed much to protect this realm, relinquishing their sight and their tongues to preserve this archive, and also of those who are intent on its destruction. Together with Mirabel, a fierce, pink-haired protector of the place, and Dorian, a handsome, barefoot man with shifting alliances, Zachary travels the twisting tunnels, darkened stairwells, crowded ballrooms, and sweetly soaked shores of this magical world, discovering his purpose—in both the mysterious book and in his own life.