The Doctor and Romana head for Calufrax in search of the second segment of the all-powerful Key to Time. But something blocks their attempts to materialise on the barren, ice-covered planet. When the TARDIS does materialise it is not on Calufrax but on the affluent world of Zanak, controlled by the Captain's harsh regime.
What is the secret behind Zanak's bountiful mines and its unseen leader? Whois really pulling the strings among the planet's rulers? What happened to Calufrax, and where is the second segment?
The Doctor, Romana and K9 must battle the ghost of a tyrant ruler from the past and stop Earth becoming the next victim of Zanak - the Pirate Planet!