The Power of the Daleks On the planet Vulcan the Doctor discovers that a human colony is under threat from a sinister, but familiar menace exhumed from the mercury swamps. The Highlanders When the TARDIS arrives in Scotland in 1746, the Doctor and Ben are able to be sold as slaves by the crooked solicitor, Grey. The Underwater Menace In the lost city of Atlantis, the insane Professot Zaroff has convinced the Atlanteans that he is going to raise their city to the surface, but in truth he intends to destroy the world. The Moonbase On the moon in the year 2070, a mysterious plague has struck the base that controls the Earth's weather - the first stage of a Cyberman plan to invade the Earth.