In the heart of London lies the Engine Ward, a district forged in coal and steam, where the great Engineering Sects vie for ultimate control of the country. For many, the Ward is a forbidding, desolate place, but for Nicholas Thorne, the Ward is a refuge. He has returned to London under a cloud of shadow to work for his childhood friend, the engineer Isambard Kingdom Brunel. Deep in the Ward's bowels, Nicholas can finally escape his strange affliction - the thoughts of animals that crowd his head. But seeing Brunel interact with his mechanical creations, Nicholas is increasingly concerned that his friend may be succumbing to the allure of his growing power. That power isn't easily cast aside, and the people of London need Brunel to protect the streets from the prehistoric monsters that roam the city. King George III has approved Brunel's ambitious plan to erect a Wall that would shut out the swamp dragons and protect the city. But in secret, the King cultivates an army of Sunken: men twisted into flesh-eating monsters by a thirst for blood and lead. Only Nicholas and Brunel suspect that something is wrong, that the Wall might play into a more sinister purpose--to keep the people of London trapped inside.