Posing as an Examiner from Earth, the Doctor warns the scientist, Lesterson about the dire consequences of reactivating the dormant Daleks.
In London in 1966, the Doctor and Dodo visit the new Post Office Tower and are introduced to the super computer, WOTAN.
As a battle rages between the rebels and the loyal colonists, the Daleks begin their attack. The only chance of survival for the colony rests with the Doctor.
WOTAN has put in motion its plan to dominate the world and has ordered its human subjects to construct deadly war machines in secret locations.
Polly is taken prisoner by the rebels who intend to use the Daleks to take control of the colony. The Doctor discovers that all three Daleks have now been reactivated.