Parts: 4
Writer: Terry Nation
Airdates: 22 November 1975 - 13 December 1975
Production Code: 4J

Doctor: fourth
Companions: Sarah, Harry

Creature Feature: Kraals
Special Guests: UNIT (Benton)

Story: Sarah is elated to return to Earth, immediately savoring the fresh smell of a recent rainstorm. But just as immediately, the Doctor notices something amiss - despite the smell, the ground is bone-dry. And things just keep getting weirder. While wandering the countryside, the Doctor and Sarah come across a group of men in astronaut-style suits in a field, but rather than a friendly welcome, they are greeted by weapons fire. Then, following a narrow escape, Sarah is horrified to see a UNIT soldier, apparently suffering from seizures, fling himself over a cliff.

The Doctor and Sarah eventually come to the quaint English town of Devesham, where Sarah had visited years before on a story. Investigating the pub, which looks oddly abandoned, they find a till full of shiny new coins, all minted the same year. When Sarah informs the Doctor that Devesham is near the Space Development Centre, the Doctor develops a nasty theory...a radiation leak might have contaminated the nearby countryside, causing evacuation and a need for fresh currency. And, Sarah realizes with horror, they have been wandering around with no idea of the danger.

A noise alerts them to a vehicle entering the village square. Several of the astronauts are escorting a truckload of villagers home - and among them, with nary a scratch, is the UNIT soldier that Sarah watched plummet to his death. The villagers enter the pub and sit stock still until the chime of the clock, when they suddenly become animated and friendly - but only among themselves, which Sarah discovers when she tries to start up a conversation with the landlord. Things are definitely out of the ordinary in Devesham, and the Doctor and Sarah come to realize that they have stumbled upon a plan to take control of the entire Earth...