Exiled to Earth in his third incarnation, the Doctor (Jon Pertwee, making his first appearance) and new companion Liz Shaw (Caroline John) helps the scientific investigation force known as U.N.I.T. defeat an army of plastic mannequins created by an alien intelligence to take over the Earth, in "Spearhead from Space." Then, experiments at an atomic research plant awaken a race of intelligent reptilian humanoids who ruled the Earth millions of years ago and are ready to reclaim the planet, in "Doctor Who and the Silurians." Can the Doctor find a way to make peace? In "The Ambassadors of Death," a manned Earth-to-Mars mission can't be located and a three-person rescue mission also disappears after returning to Earth, leading the Doctor and Liz to discover a dangerous scheme involving alien emissaries and a renegade general. And, "Inferno" is an advanced drilling project to tap into a new energy source under the Earth's crust, but a mysterious underground gas transforms men into ape-like creatures. The Doctor finds himself trapped in a parallel universe as he tries to shut down the drilling and save the planet.25 episodes on 8 discs. 10 1/3 hrs. Standard; Soundtrack: English; Subtitles: English.