The Doctor and his companions arrive in a London very different from what they remember.
The Daleks have conquered the Earth. Susan and Barbara have joined the human resistance who launch an attack on the Dalek flying saucer where the Doctor and Ian are prisoners.
The rebel attack on the Dalek flying saucer has been defeated. London is crawling with Daleks and Robomen, and the Doctor, Barbara and Susan must escape the city.
Barbara realises how to control the Robomen and orders an attack on the Daleks.
Barbara is put to work in the Dalek mine where it is revealed that the Daleks intend to use a bomb to extract the Earth's magnetic core.
