Lenora returns to the magical Library-- which holds every book ever known on its shelves. But she discovers the Library is under new management, its incredible rooms and corridors turned dark and sinister. She quickly connects with a secret resistance that’s trying to free knowledge from the shadows threatening it. Her new friends introduce her to an ancient lost city, hang gliding, and mathematical beings larger than the universe itself. And they help her face the mysterious Board of new leaders-- who must be stopped from leading the Library into darkness.