With two of the Mortal Instruments now in Valentine's hands, the world of the Shadowhunters teeters on the brink of civil war. And the search has begun for the last of the Instruments, the Mortal Glass. Clary finds herself caught up in the chaos as the delicate social order of the Nephilim begins to shatter. When the City of Glass falls under attack, can Downworlders and Nephilim fight together to defeat Valentine, or will their longstanding hatred destroy them all? And when Clary discovers the unbelievable truth about her own past, can she find Jace before it's too late?