In book four of "The Mortal Instruments" series, Clary Fray is back in New York City. She is training to be a true Shadowhunter and preparing for her mother's wedding to Luke. More importantly, she and Jace are now openly together. It's not long before nefarious forces begin to try and destroy the fragile peace between the Shadowhunters and Downworlders. Shadowhunters are being killed. As the mystery deepens, Jace starts to distance himself from Clary and all those that love him. Has Valentine returned seeking vengeance? Or is there something even more evil stirring?