Doc and Sarah match wits with finger-blasting androids and two walnuts from space planning to invade Earth
The Fourth Doctor and companion Sarah Jane Smith arrive in what purports to be rural Devesham, a picturesque hamlet in Oxfordshire with Space Defence Station adjacent, whose inhabitants have seemingly nearly all vanished without a trace.
Sarah Jane recognises the place as she once visited the Space Defence Station to enquire about the lost astronaut Crayford. What few people remain in the town, however, are android facsimiles, including Benton and Harry Sullivan who happen to be on site, and our intrepid duo doesn’t know quite whom to trust.
Eventually they discover that two curmudgeon alien chaps are preparing an invasion of Earth, and have created a replica of Devesham as their training ground. Enter stage right, monocular astronaut and narrative coincidence Crayford who may be in cahoots with the aliens. Hilarity ensues.