Alec Wallis

An isolated, overweight girl with a penchant for shoplifting, gets pushed from pillar to post as the authorities struggle to know what to do with her.

Arriving on Space Station Nerva in its distant past, the Doctor, Sarah and Harry find its crew threatened by a mysterious plague. Discovering that things are not as they seem, they uncover a Cyberman plot to destroy Voga, planet of gold.