The TARDIS lands in a ruined and empty London in the 22nd Century, as Robomen patrol the shattered streets. The Doctor and his friends are eager to discover the cause of the city's plight.
The rebel attack on the Dalek flying saucer has been defeated. 22nd Century London is crawling with Daleks and Robomen, and the Doctor, Barbara, and Susan, must try to escape the city.
The Daleks have conquered Earth. Susan and Barbara have joined the human resistance, who launch an attack on the Dalek flying saucer where the Doctor and Ian are held as prisoners.
Ian plans to derail the Daleks' plan by sabotaging their bomb and the Doctor works to turn the Robomen against them. Afterwards, a tearful Susan remains on Earth with her new love.
The Doctor, Barbara, and Susan, make their way out of London to the Daleks' mining operation in the city of Bedfordshire. Meanwhile, Ian comes face to face the Black Dalek's pet Slyther.