The New Doctor arrives on Earth in the middle of a freak meteor shower. Faceless killer shop window dummies are coming to life and killing anything that comes into their path while Facsimiles are replacing top Military, Political and Civil leaders. The Nestene has come to invade the Earth. The convalescent Doctor teams up with Brigadier Lethbridge-Stewart and Dr. Elizabeth Shaw of UNIT to thwart the Nestine's plans even as the invasion begins.

Retired commander of the United Nations' Intelligence Taskforce, and long-time associate of the mysterious time traveler the Doctor, Brigadier Alistair Lethbridge-Stewart faces the toughest battle of his military career when he is embroiled in a plot unwittingly set in motion by university chancellor Victoria Waterfield, herself a former companion of the Doctor, to take over the Earth by an evil alien entity called the Great Intelligence, aided by its ferocious robot Yeti cohorts. Can the Brigadier defeat this menace to the Earth without the Doctor's help?