Someone is murdering Shadowhunters, provoking tensions between Downworlders and Shadowhunters that could lead to a second, bloody war. Clary's best friend, Simon, can't help her -- his mother just found out that he's a vampire, and now he's homeless. When Jace begins to pull away from her without explaining why, Clary is forced to delve into the heart of a mystery whose solution reveals her worst nightmare: she herself has set in motion a terrible...