London, 1963. Schoolteachers Ian Chesterton and Barbara Wright are perplexed by the behaviour of one of their pupils, Susan Foreman. Her knowledge of science and history exceeds theirs, yet she seems totally ignorant of many common aspects of everyday life. They follow her to her home address, a junkyard with a police telephone box standing in it, and encounter her grandfather, the enigmatic Doctor. When they force their way past him into the police box, Susan's secret is revealed: she and the Doctor are aliens, and the police box is a time machine, the TARDIS, capable of visiting any point in the universe at any moment in time…

Earth, 100,000 B.C. The enigmatic Doctor, afraid that schoolteachers Ian Chesterton and Barbara Wright will reveal his secrets to the people of 20th century Earth, has taken them and his granddaughter Susan back to the dawn of human history. There, the four travellers are dragged into the savage politics of a tribe of cavemen who have lost the secret of making fire…

Prisoners of the earliest humans, the TARDIS crew are caught in a deadly power play for leadership of the tribe.

The TARDIS crew must make fire for the early humans to stay alive. But once they do, they may not be allowed to leave!

Time Unknown, Planet Unknown. The TARDIS lands in an eerie petrified forest overlooking a magnificent steel city. The Doctor wants to explore the city – but what is waiting there?

The dead planet is not uninhabited after all. The Doctor is about to meet what will become his greatest enemies. And he and his crew are dying of radiation sickness.

Imprisoned on Skaro by the scheming Daleks, the Doctor and his companions work to escape their clutches.

The time travellers work desperately to both escape the Dalek city and prevent a bloody massacre.

The time travellers have escaped from the Daleks, but left a vital piece of the TARDIS behind. Getting it back will mean pushing the Thals to mount a dangerous operation.

Ian, Barbara and the Thals struggle through the caves to reach the Dalek city. Will they get there in time? Is there even a way through the treacherous caves? And what are the Daleks planning?

Time is running out as the Doctor and his companions try to defeat the Daleks before they wipe out all life on Skaro.

A mysterious explosion has knocked the TARDIS into void. And in their confusion, the crew are turning on one another.

The TARDIS is adrift, the crew turning on each other. Only by working together can they find their way out before they are destroyed.

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.

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 solves the murder mystery and finds the final missing key. With Ian now free, the travellers return to the island only to discover that Arbitan has been murdered.

The TARDIS lands inside an Aztec temple in 15th Century Mexico and become cut off from the ship when they leave the temple to explore.

The High Priest of Sacrifice, Tlotoxl begins to doubt Barbara's claim to be the reincarnation of Yetaxa and plots to undermine her position and eliminate her friends.

The Doctor and Ian attempt to find a way back to the TARDIS. Barbara attempts to distract Tlotoxl but the High Priest of Sacrifice already has plans for Susan.

Tlotoxl is preparing to make his move and have Barbara, the Doctor, Ian and Susan killed. Ian prepares for a fight to the death with the warrior, Ixta.

The 28th century. The TARDIS materialises on a spaceship orbiting a planet known as the Sense-Sphere, whose natives, the Sensorites, have trapped the ship's human crew in a state of paralysis.

The Doctor and his companions are on board an Earth ship trapped in orbit around the Sense-Sphere when it is boarded by the Sensorites, who steal the lock mechanism from the TARDIS.

The Doctor and his companions are escorted to the Sense-Sphere where they attempt to negotiate with the Sensorites for the release of the TARDIS.

Trapped on the Sense-Sphere, Ian is dying from the illness that has been killing the Sensorites and the Doctor tries to find a cure.

Trapped on the Sense-Sphere, the Doctor's investigations into the cause of the sickness affecting the Sensorites are hampered by the subversive activities of the City Administrator.

Trapped on the Sense-Sphere, the Doctor and his companions find three deranged human survivors who have been fighting a guerilla war against the Sensorites.

When the Doctor attempts to return Ian and Barbara to their own time, the TARDIS actually lands in 18th-century France during the French Revolution.

In Paris, Ian, Barbara and Susan are sentenced to death under the blade of the guillotine. Having escaped the burning farmhouse, the Doctor is on his way to rescue his friends.

Barbara and Susan are saved from the guillotine by two royalists, Jules and Jean, but Susan has fallen ill. At the prison, a stroke of luck provides Ian with a chance to escape.

Susan is now very ill and in desperate need of medical help. The royalist, Leon, arranges for Barbara to take Susan to a physician, but the physician betrays them.

The Doctor is reunited with Barbara at the prison and arranges for her to escape, but Susan remains behind bars. Jules rescues Ian, killing Leon in the process.

The Doctor leads Lemaitre to the royalist house where Lemaitre reveals that he is in fact the English spy, James Sterling.