The story of four women who set out to uncover the secret origins of an intricate, magical city—and to change its fate. Istehar Sha'an, whose unique powers allow her to communicate with trees and books, has led her community of refugee forest people to a remarkable place. In the archipelago-city of Moonstone, the Sha'an people find themselves in an extraordinary, multicultural metropolis that houses the Library: the world's all-encompassing repository of wisdom. But in their search for a new home, the refugees soon garner the suspicion of Moonstone's locals, who forbid their magical practices. And when a hostile prince makes a bid to inherit the city's rule from his father, Istehar and her people realize they may be faced with exile—or worse. Meanwhile, Istehar has married three wives of Moonstone—a brave warrior librarian, a subtle-minded former concubine, and a tenacious apothecary who has spent years trying to solve her parents' murder. Driven by magical intuition and guided by a mysterious book, Istehar and her wives embark on a journey that will transform not only their lives, but the city of Moonstone itself.