The Moonbase

From http://www.bbc.co.uk/doctorwho/classic/episodeguide:

The TARDIS arrives in 2070 AD 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.

Polly realises that as the Cybermen's chest units are made of plastic they must be vulnerable to attack by solvents. She and her friends manage to destroy all the Cybermen on the base with a 'cocktail' of such chemicals shot at them through fire extinguishers.

A second wave of Cybermen advances across the lunar surface but, prompted by the Doctor, Hobson uses the base's gravity-generating weather control device, the Gravitron, to send them flying off into space.

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