The Infernal Devices: Clockwork Prince (The Infernal Devices, 2) (Volume 2);

Tessa Gray has found friends among the Shadowhunters, supernatural protectors of mankind who possess angelic blood. But Tessa's new life is threatened when some members of the Clave challenge Charlotte's leadership and pressure her to resign. If Charlotte is forced out, Tessa will have to leave as well, making her easy prey for the still-at-large Magister! Will and Jem are determined not to let this happen, but sometimes danger comes from where it's least expected...