Having upset the balance between the warring statues of London, twelve-year-old George is confronted with new challenges as he tries to free his captured friends Edie and The Gunner from the formidable Walker and deal with the three strange veins of marble, bronze, and stone that have begun to grow out of his hand.

The five remaining members of the Oversight, a dwindling organization that polices the boundary between the mundane and the magic, struggle to keep up as brutal murders break out across London and their enemies draw closer.