Animated reconstruction of the lost four-part serial from the fourth series of the sci-fi adventure drama starring Patrick Troughton as the legendary Time Lord. In this instalment, the Doctor is joined by companions Polly (Anneke Wills), Ben (Michael Craze) and Jamie (Frazer Hines) as he investigates a mystery on one of Earth's future colonies, where the inhabitants are being controlled by giant insects called the Macra. Can the Doctor find out what the creatures want with the colony and stop them before it's too late?