Danger intensifies for the Shadowhunters in the harrowing last installment of the Infernal Devices trilogy. Seventeen-year old Tessa Gray should be happy as she prepares for her wedding to Jem Carstairs. But a new demon appears, one linked by blood and secrecy to the Magister, the man who plans to use his army of pitiless automatons to destroy the Shadowhunters. He needs only one last item to complete his plan of destruction, Tessa. The London Institute rallies to save her, but is beset by danger and betrayal at every turn.