The TARDIS materializes on the Moon in 2070.  A control station is located there that controls the Earth's weather.  The base is experiencing a plague which is reality is a poison from the Cybermen.  Once they are revealed, Polly figures out that as their chest units are plastic and hence they must be vulnerable to solvents.  They are able to destroy the Cybermen with fire extinguishers loaded with these chemicals.

A second wave begin their attack on the base.  They are crossing the Moon's surface when the humans use the base's Gravitron to send them into space before they can reach it.