Doctor Who: The Ribos Operation (TV)

The White Guardian gives the Doctor a quest to find the six disguised segments of the Key to Time which, when assembled, will be used to restore the balance of the cosmos. To aid him he is given a new companion, a female Time Lord called Romana, and a tracer device. He tracks the first segment to the city of Shur on the planet Ribos. There con men Garron and Unstoffe are engaged in a scam to sell the entire planet to the Graff Vynda-K, deposed ruler of Levithia. The Graff has been tricked into believing that Ribos is a rich source of jethrik, a rare mineral vital for achieving space warp drive.