The alien world of Lakertya. With the aid of the savage Tetraps, the Rani has conquered this planet to allow her to continue her depraved biochemical experiments. But she finds herself needing the Doctor's assistance...

The Rani's impersonation of Mel backfires badly because Urak can't tell the difference, while the Doctor attempts to learn the secret of the Loyhargil.

The solstice nears, making it time for the Rani to bring her plans into fruition. The Doctor's sympathies for Beyus, ruler of the Lykertyans, are rather qualified. Beyus' heart is for his people yet something prompts him to collaborate fully in helping the Rani reach all her objectives. The answer, he's told, lies within the Center of Leisure.

The Rani, at last, links the Doctor into her great brain machine, the crowning jewel in her component packet of geniuses brought together to turn Lakertya itself into one vast cerebral mass capable of redirecting time anywhere in the universe, giving her absolute power over all creation.

London, 1963. Returning to the scenes of his first televised adventure, the Doctor and new companion Ace play a tricky game of bluff and deceit involving two rival Dalek factions, local soldiers, and the awesomely powerful Gallifreyan artefact, the Hand of Omega...

With two factions of Daleks involved in a race war on Earth, the Doctor takes care of old business by having the Hand of Omega ceremoniously but quietly buried in a churchyard. His actions do not go unobserved, and leaving behind a bored Ace without a purposeful outlet could spell trouble as well.

The Doctor plans to let one of the Dalek factions have the Hand of Omega (but not too easily, of course) while keeping Gilmore and his military men preoccupied in a safe territory, but that plan could be threatened by a mole in their midst and a miscalculation on the Doctor's part.

The Omega device is in jeopardy. A giant Dalek warship hangs above the Earth. London has become a battleground for ruthless alien intelligences.