An energy drain traps the Third Doctor and Sarah Jane Smith on the planet Exxilon with its hostile natives, causing the travellers to make an uneasy alliance with a Marine Space Corps expedition and a squadron of Daleks. The key to escape for all of them lies at the heart of a powerful and mysterious lost city, but only after a series of deadly traps.

The planet Peladon has applied to join the Galactic Federation, and The Doctor is mistaken for the chairman of the committee sent to assess its application, while Jo is taken for an Earth princess, with the mythical curse of Aggedor apparently striking chancellor Torbis dead, The Doctor must discover who is desperate to stop Peladon joining, but soon he is sentenced to death and his only Allies seem to be Jo and the Ice Warrior Delegates.

Guerillas time-jump back from the 22nd century to assassinate Sir Reginald Styles - a diplomat working for World Peace, The Doctor discovers they are from a future where the Daleks have invaded the Earth (Following wars precipitated by Styles's destruction at the peace conference). With the Daleks desperate to maintain their version of history, The Doctor and Jo find themselves in a totalitarian future, where they must discover who really happened and prevent it.

The Daleks draft the Second Doctor into distilling the Human Factor. Once implanted, it will make the Dalek race invincible. Jamie's faith in the Doctor is stretched to the limit as the Doctor appears to be collaborating with the Daleks. The Doctor has a few tricks up his sleeve, but then again so might the Daleks.

The Doctor and his companions are pursued through time and space by the Daleks on the desert planet Aridius and beyond.

On the planet Xeros, the TARDIS crew discover their own future selves frozen in time as exhibits in a galactic museum and must avert this potential future.

The adventures of The Doctor, a time-traveling humanoid alien known as a Time Lord. He explores the universe in his TARDIS, a sentient time-traveling spaceship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Along with a succession of companions, The Doctor faces a variety of foes while working to save civilizations, help ordinary people, and right many wrongs.

The adventures of The Doctor, a time-traveling humanoid alien known as a Time Lord. He explores the universe in his TARDIS, a sentient time-traveling spaceship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Along with a succession of companions, The Doctor faces a variety of foes while working to save civilizations, help ordinary people, and right many wrongs.

The adventures of The Doctor, a time-traveling humanoid alien known as a Time Lord. He explores the universe in his TARDIS, a sentient time-traveling spaceship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Along with a succession of companions, The Doctor faces a variety of foes while working to save civilizations, help ordinary people, and right many wrongs.