Clockwork Prince (Book 2 - Infernal Devices Series)

In the magical underworld of Victorian London, Tessa Gray has at last found safety with the Shadowhunters. But that safety proves fleeting when rogue forces in the Clave plot to see her protector, Charlotte, replaced as head of the Institute. If Charlotte loses her position, Tessa will be out on the street and easy prey for the mysterious Magister, who wants to use Tessa's powers for his own dark ends.