Even as time goes on, the Shadowhunters of the New York institute must continue to protect mundanes and fulfill their holy mission to the angel Raziel. Zia Nightshade, daughter of Simon Lewis and Isabelle Lightwood must continue her family name, and save the world from the sudden influx of demons from the Demon Realms. Dimensions are becoming easier to travel through, and only one sacrifice can save them. Zia is their last chance, their last instrument of chaos.