The Doctor in Front of the Time-Space Visualiser

In the TARDIS, The Doctor and his three travelling companions (Barbara Wright, Ian Chesterton and Vicki) are huddled around the Time-Space Visualiser, a souvenir they obtained from their recent adventure at the Space Museum. This television-like device can pick up on any past event in the whole of time and space. They each choose an event to witness: Ian picks Abraham Lincoln giving his Gettysburg Address; Barbara elects to look into Elizabeth I's court, and sees the genesis of two Shakespeare plays (‘The Merry Wives of Windsor’ and ‘Hamlet’) while Vicki sees the Beatles performing ‘Ticket to Ride’.

The TARDIS then materialises on the desert planet Aridius and The Doctor confirms that the conditions are hospitable so Ian and Vicki leave to explore the desert wilderness. Vicki becomes intrigued by some formations which appear similar to seaweed. They then find a trail of what appears to be blood in the sand, which Vicki runs off to follow. However, as they move off, they do not notice a tentacle rise up from the sand where they had just been standing.

While The Doctor and Barbara are sunbathing Barbara becomes distracted by the sound of the Visualiser, which had not been shut off. When she enters the TARDIS she sees the Daleks preparing to give a report. The Doctor enters and hears, to his horror, the Daleks' plan to follow what they describe as ‘the enemy time machine’ - which can only mean the TARDIS - to the Sagarro Desert on the planet Aridius.

The Daleks Surround the TARDIS

The Daleks are planning to track down the TARDIS and then exterminate them. The Doctor and Barbara then watch the Daleks enter a machine which then dematerialises. The Doctor immediately realises that these events happened in the past and so the Daleks may already be on Aridius. They therefore must find Ian and Vicki and leave immediately.

Ian and Vicki though have become trapped in an underground cavern with more of the tentacled creatures (known as Mire Beasts). It is because of this that The Doctor and Barbara have had no luck in finding their friends. The Doctor and Barbara soon become lost when the wind picks up, covering all tracks including their own. A sandstorm then breaks out which lasts all night.

Barbara on the Deserted Marie Celeste

When they awake in the morning they are shocked to see a Dalek, buried by the sandstorm, emerging from the sand. Two other Daleks then arrive. The Doctor and Barbara realise that the Daleks may have not discovered the time travellers themselves, but they have located the TARDIS under the sand and have begun to have it dug out by a group of native Aridians, whom they have enslaved. This slave force is then exterminated when they are of no further value.

The Daleks have also made contact with the Aridians in an underground city and they tell them that they will leave Aridius if The Doctor and his party are handed over to them. The elders agree to this arrangement as they have already found Ian and Vicki, who were injured when a wall collapsed in an explosion used to kill the Mire Beasts that were threatening the underground city. The Mire Beasts though soon reappear, killing the Aridians who are holding Ian and Vicki prisoner in preparation for their handover to the Daleks. After following the Daleks to the underground city The Doctor and his friends flee in the confusion and manage to evade a Dalek scout before reaching the safety of TARDIS. But soon after they leave Aridius, The Doctor realises that the Daleks are in hot pursuit and they are but fifteen minutes behind with the gap closing. The chase is on…

In trying to shake off their pursuers The Doctor pilots the TARDIS by taking in a number of stopping-off points. These include the observation gallery of New York's Empire State Building, a 19th Century sailing ship that turns out is the Marie Celeste and a spooky haunted house which, although The Doctor and his friends do not realise it, is actually a futuristic fun-fair attraction.

A Dalek on the Marie Celeste

Eventually both time machines arrive on the jungle planet Mechanus, where the Daleks try to infiltrate and kill The Doctor's party using a robot double of him. However, unbeknown to both sets of time travellers Mechanus is occupied by a group of robots sent some fifty years earlier to prepare landing sites for human colonists. Called Mechanoids these robots capture The Doctor and his companions where they meet Steven Taylor, a stranded astronaut who has been the Mechanoids' captive for the past two years.

Still pursuing The Doctor the Daleks enter the Mechanoid's city and find themselves engaged in a fierce battle which ultimately results in their mutual destruction. The Doctor and his three companions, along with Steven, seize this opportunity to escape and they all manage to get away as the city burns.

Back at the TARDIS Barbara and Ian realise that by using the Daleks' now-abandoned time machine, and with The Doctor’s help, that they can at last return home to 20th-century Earth. Once his initial objections have died down, The Doctor reluctantly helps them to do so. And so after a short trip Ian and Barbara find themselves delighted to be back home. Although they quickly realise that they have in fact arrived in 1965, two years later then when they left, leaving them with the difficulty of explaining their long absence!

Meanwhile, The Doctor is left to operate the TARDIS controls with just Vicki accompanying him and, unbeknown to them both, a stowaway.