In a future Chicago, sixteen-year-old Beatrice Prior must choose among five predetermined factions to define her identity for the rest of her life, a decision made more difficult when she discovers that she is an anomoly who does not fit into any one group, and that the society she lives in is not perfect after all.

As the Council attempts to strip Charlotte of her power, sixteen-year-old orphaned shapechanger Tessa Gray works with the London Shadowhunters to find the Magister and destroy his clockwork army, learning the secret of her own identity while investigating his past.