The TARDIS arrives in 2070 on the Moon, where a weather control station under the command of a man named Hobson is in the grip of a plague epidemic — in reality the result of an alien poison planted by the Cybermen. Jamie is knocked unconscious and lapses into a delirium, leaving the Second Doctor, Ben, and Polly to fight off a massive Cyberman attack.
| Actor | Role |
|---|---|
 Patrick TroughtonThe Doctor | The Doctor |
 Anneke WillsPolly | Polly |
 Michael CrazeBen Jackson | Ben Jackson |
 Frazer HinesJamie McCrimmon | Jamie McCrimmon |
 Patrick BarrHobson | Hobson |
 André MaranneBenoit | Benoit |
 Michael WolfNils | Nils |
| JJohn RolfeSam | Sam |
| MMark HeathRalph | Ralph |
 Alan RoweVoice from Space Patrol/Dr. Evans | Voice from Space Patrol/Dr. Evans |
| DDenis McCarthyVoice of Rinberg | Voice of Rinberg |
| BBarry AshtonScientist | Scientist |
| DDerek CalderScientist | Scientist |
| AArnold ChazenScientist | Scientist |
| LLeon MaybankScientist | Scientist |
| VVictor PembertonScientist | Scientist |
| EEdward PhillipsScientist | Scientist |
| RRon PinnellScientist | Scientist |
| RRobin ScottScientist | Scientist |
| AAlan WellsScientist | Scientist |
| MMark HeathScientist | Scientist |
 John MaximCyberman | Cyberman |
| SSonnie WillsCyberman | Cyberman |
| PPeter GreeneCyberman | Cyberman |
| KKeith GoodmanCyberman | Cyberman |
 Reg WhiteheadCyberman | Cyberman |
 Peter HawkinsCyberman Voices | Cyberman Voices |