“The Krotons have always been our friends, our benefactors!”
The TARDIS arrives on a planet which is home to the humanoid Gonds. Ruling over these people are the Krotons, crystalline beings who crash-landed there centuries before. Currently in suspended animation, the Krotons can only be reconstituted by and influx of mental energy.
Twice a year, the most capable Gond students are taken into the Krontons’ spaceship, the Dynatrope. Apparently, they have been chosen to live alongside their masters – but, in fact, they are drained of all mental energy and then killed.
When The Doctor, Jamie and Zoe befriend the Gonds, they find a community divided by their servitude to the Krotons. Then The Doctor and Zoe take the Krotons’ mental ability test – and unwittingly help revive the crystalline monsters…