In a Victorian Gothic mansion, strange things are afoot. The master of the house, away in Egypt, has been replaced by a sinister Egyptian. Cloth-wrapped Mummies roam the grounds, killing people. Beneath a pyramid, the last of the Osirans — Sutekh the Destroyer — waits to be freed, to at long last bring his gift of death to all who live.

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.

Arriving on the barren world of Androzani Minor, the Doctor and Peri find themselves embroiled in a long running, literal underground war. At the heart of the conflict is a substance called Spectrox - both valuable and deadly! The Doctor & Peri wind up being poisoned by the material, which is killing them slowly and painfully unless they can find a cure. As the conflict heats up and the situation gets more desperate, the Doctor realises time is running out - both for Peri and himself...