19th century Lancashire: the white heat of the Industrial Revolution burns hottest at Samuel Belfrage's brass mill, a mill plagued by more than its fair share of work-related injuries.

While Thomas Brewster struggles to secure a fair deal for Belfrage's overworked hands, fellow travellers the Doctor and Evelyn follow the Copper King to Liverpool, there to discover the unexpected truth about Belfrage's business.

Back in Ackleton, the local MP voices the fears of many when he says that the machines are taking over. He's more right than he knows…