The peasants are revolting in the 19th Century England, when the Doctor and Peri arrive. As Luddite attacks in the village increase, an old enemy of the Doctor's is revealed.
The Master wants to use the finest brains of the Industrial Revolution to speed up Earth's development and then use the planet as a power base. He strikes a deal with the Rani.
Peri is making herself useful by using her botanical knowledge to make a sleeping draught for the afflicted miners. Her quest for herbs leads her to Redfern Dell.