The Doctor returns Grant to his home planet Agora. Upon arrival they discover 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. As rebellion is plotted, there is another time traveller at work: the Cybermen obsessed Archivist Hegelia, and her novice research partner, Graduand Jolarr. Can the Doctor save the day when locked away in a cell?
Influences
The design of the Cybermen explicitly described in this story is the design used in the 1975 Doctor Who television serial "Revenge of the Cybermen" as developed by BBC costume designer Prue Handley.
Details about the Cybermen including the term "CyberNomad" and references to Cyber-history, as well as the character of Hegelia and the Arc Hive from which she operates were originally conceived by David Banks for Cybermen, a study of the Cybermen both as a concept and a factual possibility and used with Banks's permission.
References
^Wolverson, E.G. "Killing Ground". Doctor Who Reviews. Retrieved 17 November 2014.