The Krotons — Robert Holmes

Patrick Troughton stars as the second Doctor in this remastered soundtrack of a classic television adventure, with linking narration by Frazer Hines.

"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 an influx of mental energy.

Twice a year, the most capable Gond students are taken into the Krotons 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.