The situation at the London Institute has never been more precarious. With Mortmain and his clockwork army still threatening, the Council wants to strip Charlotte of her power and hand the running of the Enclave over to the unscrupulous and power-hungry Benedict Lightwood.
In the hope of saving Charlotte and the Institute, Will, Jem and Tessa uncover information about the man they know as “Mortmain”: He is really someone else entirely–someone who blames the Shadowhunters for the murder of his parents nearly a half century ago. But who were his parents, and why did the Shadowhunters kill them? Determined to unravel the secrets of his past, the trio journeys to mist-shrouded Yorkshire, to investigate a past that holds the key not just to the enemy’s motivations, but ot the secret of what Tessa really is and what she was born to do.
Meanwhile, Tessa finds herself drawn more and more closely to Jem, while Will, desperate not to lose Tessa but still believing himself under a curse, begs Magnus to find a way to help him. When Tessa learns the truth about who she is, and the part the Shadowhunters have played in making her a “monster,” will she turn from them to her brother, Nate, who has been begging her to join him at Mortmain’s side? Where will her loyalties–and love–lie? Tessa alone can make the choice that will save the Shadowhunters of London–or end them forever.