The Earth is endangered by a renegade Time Lord known as the Master, who steals a dormant Nestene energy unit from a museum. He reactivates it using the facilities of a radio telescope, then uses his hypnotic abilities to take control of a small plastics manufacturer, Farrel Autoplastics, where he organises the production of deadly Auton artefacts, including plastic dolls, chairs and daffodils. The Master has an evil scheme to destroy humanity and to silence his old foe, the Doctor, forever. He plans to awaken the awesome power of the Nestenes, a ruthlessly aggressive alien life form. The Nestenes can control anything made of plastic, including killer Autons: plastic mannequins, faceless but possessing a shared consciousness. The Autons form an army of invasion, easily controlled by the Master himself. This is the terrible threat facing Earth — the terror of the Autons. Aided by the Brigadier, and by new companion Jo Grant, only the Third Doctor can combat their evil power, but first he must defeat the Master...