The White Guardian sends Doctor and a recently graduated female Time Lord to find the six segments of the Key to Time. With Tom Baker.

The Doctor urges peace upon quarreling travelers aboard a large ark journeying 700 years to a new planet, Refusis, as the Earth is about to plunge into the sun. With William Hartnell.

The Doctor urges peace upon quarreling travelers aboard a large ark journeying 700 years to a new planet, Refusis, as the Earth is about to plunge into the sun. With William Hartnell.

The Cybermen are on the march; as the last remaining humans are ruthlessly hunted down, Graham, Ryan and Yaz face a terrifying fight for survival.

The Doctor and Clara are inundated with ghosts from the past and the future.

As they slowly recover from the shock of being thrown to the Tardis floor, the Doctor, Susan, Ian and Barbara all seem to be acting strangely. A number of unexplained events occur and suspicions are raised that some alien force may have entered the ship.

The Tardis lands on a remote island, surrounded by a sea of acid. They meet Arbitan, keeper of the Conscience of Marinus who forces the travellers to go in search of five keys.

In the city of Morphoton, the Doctor, Barbara, Ian and Susan are welcomed as honoured guests and given anything they want. But Barbara soon discovers that paradise is an illusion.

Ian and Barbara find a temple in the middle of a hostile jungle. Inside is the ailing Darrius, keeper of one of the keys. As Darrius dies he gives Ian a clue to find the key.

In a snowy wasteland, Vasor, an unscrupulous trapper, imprisons the travellers in a frozen cavern inside a mountain. There they find one of the keys frozen in a block of ice.

A mysterious woman who can't even remember her own name, falls from the sky.

Arriving in the city of Millennius, Ian is put on trial for murder. The Doctor takes on the role of defence counsel and must prove Ian's innocence or he will be executed.

The Doctor must find the four lost keys of Marinus.

On Halloween, all across the universe, terrifying forces are stirring; from the Arctic Circle to deep space, an ancient evil is breaking free; in present day Liverpool, the life of Dan Lewis is about to change forever.

The crew venture out of the Tardis into 15th Century Mexico and the tomb of the Aztec High Priest Yetaxa. When Barbara stumbles upon the Aztecs they mistake her for a reincarnation of the High Priest himself.

Barbara's interference in the Aztec practice of human sacrifice casts doubt over her supposed divinity and puts the whole crew in jeopardy.

It is the day of the solar eclipse when Susan is to be punished for her refusal to marry. The Doctor and his companions try to escape before they are sacrificed to the Sun God.