In the sequel to Ex Magica, the heirs of the Triad find themselves cut off from all they have ever known. Mallory and Caleb are married now and must learn to navigate their relationship without alienating Alex, who with her magisterial training protects the young couple from dangers found outside the safety of their city. A curious clockwork sprite leads the group farther into the wilderness toward a mysterious Library and the hope of a new life. Along the journey, they uncover mass destruction, battle carnivorous beasts, face sinister betrayal, and flee from the Ex Natu, an ancient people who created the fire sprites that nearly destroyed their family, their homes, and everything they loved. Somehow, the clockwork sprite seems to be as afraid of these ancient threats as it is of Mallory herself. Can the heirs learn the reason for the sprite's fears at the Library? Are the Ex Natu the lost generation who vanished so many years ago, or are they something more nefarious? And just who can the heirs trust on this strange journey?