-> ''There are some corners of the universe which have bred the most terrible things. Things that act against everything we believe in. They must be fought.''
-->-- '''The Doctor'''
Cybermen on the Moon, as the perennial favourites make their second appearance in essentially a retread of their first.
It's 2070 AD and Earth's weather is controlled from a station on the Moon by means of the Graviton. The crew of the station are coming down with a disease that turns out to be a Cyberman-engineered poison. Polly and Ben realise that as Cybermen are part-plastic, solvents ought to harm them, and mix up a cocktail of chemicals which they use in fire extinguishers to defeat the Cybermen on the base.
A second wave of Cybermen invade across the Moon's surface but the Graviton quickly sends them flying off into space and the travelers go on their merry way.
* ContinuousDecompression: This episode features the subtrope of characters struggling to seal the hole as the air rushes out. One fan actually did the calculations to see how long it should have actually taken for decompression to happen. The results were something on the order of a few seconds. The scene in the episode lasted much longer, obviously.
* CreepyMonotone: Cybermen's voice turned from bizzare singsong to a fully mechanical voice.
* MissingEpisode: Episodes 1 and 3 are missing from the BBC archives.
* MultinationalTeam: The crew of the Graviton station.
* NotHimself: Personnel under cyber-control.
* NotThatKindOfDoctor: The Doctor actually claims to have recieved a medical degree...from Joseph Lister in 1888. Polly is ...skeptical about its continued applicability.
* SmartBall: Ben Jackson suddenly has considerable knowledge of chemistry, physics, and medicine that he never displays again.
* StayInTheKitchen: Ben tries this on Polly. She doesn't listen.
* TapOnTheHead: Averted. Jamie's bump on the head is treated very seriously and keeps him bedridden for the first two episodes.
** Which actually happened because Jamie wasn't meant to stick around at first, and the writers had to rush to put him in the script.
* WeatherControlMachine: The Gravitron, situated on the moon and which controls the weather on the Earth.