Synopsis
The Doctor returns his companion Grant to Agora, the human colony planet where he was born, and upon arrival discovers that Agora has been conquered by the Cybermen, who have enslaved the population and return every three years to take the five hundred fittest humans for conversion in order to add to the Cybermen's galactic army. At the same time, Agora plays host to another time traveller, ArcHivist Hegelia, and her novice research partner, Graduand Jolarr. Hegelia is obsessed with the Cybermen and intends to become one, and she has used the sanctioned excursion of Jolarr as an excuse to meet them and arrange the fulfilment of her ambition. Agoran rebels plan an attack on the Population Control building set up by the Cybermen as a herding centre for conversion selectees with the assistance of Grant, but the Doctor is trapped in a cell inside the building, and the Cybermen are due to return in person within a matter of days.
Read more about this topic: Killing Ground (Doctor Who)