The Pirate Planet

Aboard the TARDIS: The Doctor, Romana, and K-9 scour the galaxy in search of six seemingly lost pieces of the incredibly powerful Key to Time.

They soon locate a fragment in the outer reaches of the universe on the happy and prosperous planet of Zanak. Once outside, however, they quickly realise they're in the wrong place at exactly the right time.

The planet is entering yet another New Golden Age with enough gems and minerals for every residents. So, obviously, something is very, very wrong.