Parts: 4
Writer: Douglas Adams
Airdates: 30 September 1978 - 21 October 1978
Production Code: 5B

Doctor: fourth
Companion: the first Romana, K-9 mark two

Megalomaniac of the Week: Queen Xanxia

Story: The Doctor locates the second segment of the Key to Time on the cold, wet, icy, dull planet Calufrax. But when the TARDIS materializes, it is not on Calufrax - to the Doctor's simultaneous relief and consternation.

The natives of the planet seem reluctant to tell the Doctor if they've spotted a rogue Calufrax anywhere, but he does discover that the streets are littered with extremely valuable gemstones just lying around unclaimed. His curiosity piqued by the double mystery of Calufrax and a populace blasé about immense riches, the Doctor is only too ready to investigate when he and Romana hear shouts from a nearby home. Inside, a young man is raving about Mentiads, a group of zombielike telepaths who soon come to claim him by force. Meanwhile, Romana is arrested for possessing a forbidden telescope and asking the forbidden question "Why?" She is taken to the Captain, the cyborg ruler of the planet, who forces her to help repair some of their damaged machinery.

As the Doctor and Romana are soon to discover, nothing on the planet is exactly what it seems. Not the Mentiads, not the Captain, and certainly not the planet itself, which is hiding some pretty nasty secrets beneath the surface...