The TARDIS arrives on the Moon in the year 2070.When Jamie is injured, the other travellers are forced to seek the help of a moonbase afflicted with a space plague.

The Doctor and his friends attempt to convince the Moonbase crew that the Cybermen are responsible for the disappearances and find a cure for the plague.

The Cybermen take over the Moonbase and begin using the Gravitron to attack Earth but Polly, Ben and Jamie come up with a way to fight back.

With the Cybermen preparing to launch a full attack, the Doctor and his friends must keep the Moonbase and the Gravitron out of their hands until help arrives from Earth.