The Dark War never happened, but things are still different. Clary lives with the Morgenstern family in the manor under the Clave's rule. When her parents leave for business in the Mundane World, Clary and Sebastian are sent to live with the Lightwoods, including Jace. These are the events that unfold in the days that her parents are gone.

Three years after CoHF, Jace and Clary have broke up due to Clary catching Jace kissing another girl. She hasn't seen him since the day she left him. But now, someone is killing Downworlders in New York and the Clave has paired Clary and Simon (her parabatai) with the Institute to find the killer and stop the murders. But... what about her and Jace? Will they be together once more?