On the planet Dido, the Doctor, Ian and Barbara meet two survivors from a crashed spaceship who are terrorised by the monster Koquillion.

Peter Miles stars as Tom Tiflin, the little boy at the heart of this John Steinbeck story set in Salinas Valley. With his incompatible parents -- the city-loving Fred and country-happy Alice -- constantly bickering, Tom looks to cowboy Billy Buck for companionship and paternal love.