Foulsham has been destroyed. Darkness lies heavily over the city; the sun has not come up for days. Inside the houses throughout the capital, ordinary objects have begun to move. There are rumours of a terrible contagion. From the richest mansion to the poorest slum, people have disappeared. The police have been instructed to carry arms. Someone has stolen a certain plug. Someone is lighting a certain box of matches. All will come tumbling down. The Iremongers have come to London.
The Iremongers are a mean and cruel family, robust and hardworking, living in the Heaps, a vast sea of lost and discarded items. A storm is brewing over Heap House. The Iremongers are growing restless and the whispers are getting louder. When Clod meets Lucy, a girl newly arrived from the city, everything changes. The secrets that bind Heap House together begin to unravel to reveal a dark truth that threatens to destroy Clod's world.
In the aptly named borough of Foulsham, Grandfather Umbitt Iremonger has found a way of making everyday objects assume human shape, and turning real people into objects. Lucy Pennant has been discarded as a clay button, abandoned in the Heaps. Meanwhile, Clod has been turned into a gold coin and is being passed as currency through the town. Everywhere people are searching for Clod, who, it is believed, has the power to bring the mighty Umbitt down.