Much to Peri's consternation, the Doctor is throwing himself into all kinds of chores around the TARDIS, and one particular problem he is trying to repair is the ongoing malfunction of the chameleon circuit. The Doctor, annoyed at Peri's lack of confidence in his work ethic and abilities decides that perhaps they should enjoy some leisure time...on Earth. When the TARDIS nearly collides with Halley's Comet, it would appear that Peri might be correct - the Doctor is taking on too much. A distress call, from Earth 1985, attracts the Doctor's attention and so he decides to investigate.

In London, four men are preparing for a bank job - by going through the sewer system. The leader of this group, Lytton, has encountered the Doctor before and suspects that the time traveller may arrive on Earth. However, his concern is with the alien force that has set up a base in the sewers - the Cybermen.

On the surface of Telos, adopted world of the Cybermen, two prisoners make their escape - only to discover that they are not being pursued. Their main worry is retrieving an intact Cyberman head as without it they will not be able to gain access to Cyber Control and the ship that will offer them a chance to get off Telos...

One of the main exports of Varos are recordings of executions and of the trials prisoners undergo as they attempt to escape from The Punishment Dome. Ordinary citizens watch as wrongdoers die in various ways - whether by simply laser obliteration or in one of the many traps littered throughout the Dome. It serves as a reminder to those who dare to step out of line or question the system.

The Officer Elite appear to enjoy a better lifestyle - although every so often, one of their number is elected Governor. The task of the governor is to to appease the people, to obtain a good price for whatever Varos can sell, including the mineral, Zeiton 7. The Governor must put himself before the viewing public, to allow the people to decide if he is doing a god job or not. Sometimes the majority agree...and sometimes the majority don't in which case beams of radiation bathe the Governor. The Governor can survive some of the negative votes but eventually a negative result leads to a fatal dose of radiation.

In the equivalent of a galactic layby the TARDIS has stalled. The Doctor fears that he may be trapped for centuries but after a chance remark from Peri he realises that the TARDIS requires some more Zeiton 7 to enable it to process the energy that powers it. Programming the TARDIS for Varos, the Doctor hopes they arrive during its mining period...wondering what he will find there...

The North of England in the early part of the 19th century is a time when men of science are doing their best to advance the human race into a new era of industrialism. Around the country, men worried that machines will replace them begin to attack machinery. In the village of Killingworth, a group of men, tired after a hard day in the mines, choose to take a bath at the local bathhouse. When they emerge, washed, the men appear to have changed into Luddites and set off on a wrecking spree. One of their targets is a machine destined for the nearby mine. Only the intervention of the Doctor and Peri halts greater damage.

Accompanying the driver into the village, the Doctor and Peri keep an eye on a device for registering unusual energy patterns. Originally they had planned to visit Kew Gardens but something has drawn the TARDIS off course and brought them to Killingworth. When the Doctor is attacked by some of the Luddites himself, it becomes apparent that these abrupt behavioural changes in some of the local men might be attributable to something else. Everything seems to point to the bathhouse - there the Doctor encounters both an old foe, the Master, and another renegade Time Lord - the Rani.

At the request of the Time Lords, the 2nd Doctor and Jamie arrive on Space Station Camera to negotiate with its director, Dastair. Two scientists on the station, Kartz and Rhymer, are conducting time travel experiments which the Time Lords fear are causing disruption to the time continuum. Dastari takes note that as an exile the Doctor has no official standing and the Time Lords can deny sending him. Without further evidence that the experiments are a danger, all Dastari can see is that the Time Lords perceive the experiments as a rival to their own mastery over time. When Dastari's chatalaine, Chessene, offers them refreshments the Doctor realises that she is an Androgum - but a very different Androgum from those he has encountered. After Dastari explains that Chessene has been technically augmented, the negotiations become more heated. During the argument, Dastari loses consciousness and the Doctor determines that he has been drugged. Sounds of battle echo through the station and as he stares down the barrel of a fun, the Doctor urges Jamie to run.

The 6th Doctor and Peri are enjoying a rest, the former indulging in a spot of fishing much to the annoyance of the latter. When the fishing trip doesn't quite go according to plan, the travellers return to the TARDIS. There, the Doctor appears to suffer some kind of seizure and on recovering is concerned that at some time he was being tortured, perhaps even to death. If has died in a previous incarnation it could have implications for the time line.

At Peri's suggestion he go see a doctor, the Doctor decides that he might just go and see his old friend Dastari. On arrival, they find Space Station Camera in darkness, its internal atmosphere filled with the scent of rotting meat and death. Evidence of an attack concerns them both and the Doctor voices the opinion that the station threatened nobody. The station computer replies that "it threatened the Time Lords".

Faced with the implication that the Time Lord might have resorted to extreme measures to stop rival time experiments, the Doctor must also face the possibility that an earlier version of himself was executed on the station. Further investigation seems to suggest that the answers are to be found on Earth, specifically just outside Seville in Andalucia, Spain...

A group of rebels on the planet of Karfel split up to avoid capture. Two are unsuccessful, another escapes into the inner sanctum where the Borad resides. She is killed as she learns the secret of the leader of Karfel. The captured rebels are sentenced to banishment - in the Timelash, the entrance to a time space tunnel - its exit, unknown. It is not a fate that anyone wishes to incur. Vena, the daughter of Maylin Renis, horrified at the death of her father and the assertion that he too had rebelled against the Borad, falls into the Timelash.

The Doctor and Peri are discussing their travels - the former explains about the various wonders of the universe - the amazing worlds to visit and the sights to see. The latter argues that the Doctor seems to indugle in "aimless wandering". It is not long before they encounter a time space tunnel and the TARDIS is drawn into it. As the travel through the tunnel, Peri witnesses a woman pass through to some other world and time. The Doctor remakrs that the presence of the TARDIS will have caused the tunnel to deviate from its original destination. In the meantime, they will continue on to its source - Karfel.

On Karfel, the new Maylin, Tekker, is charged with finding the amulet taken by Vena. The arrival of the Doctor is seen as fortuitous - he can be engaged into travelling to the other end of the Timelash to locate Vena and return her and the amulet to Karfel. Leverage may be required and so Peri is taken prisoner. Understanding that an oppressive regime has taken over on Karfel, the Doctor has not choice but to obey...

The Doctor and Peri have arrived on Necros, dressed in the official colour of mourning - blue. They have come to pay their respects to Arthur Stengos: his body is currently in a state of Perpetual Reinstatement at a nearby facility - Tranquil Repose. There, the bodies of many great people also lie in a state of Perpetual Reinstatment. Jobel and his funerary team are preparing the president's wife and they wait the arrival of the president himself. However, while they make their preparations, two people - Natasha and Grigory sneak into the depths of Tranquil Repose. Natasha hope to find the body of her father - Stengos, as in spite of various applications she has been refused access to it. When the finally locate the chamber in which Stengos is reposing they find instead a mannequin. How many of the other chambers no longer contain their occupants?

En route to Tranquil Repose, the Doctor and Peri encounter a mutant. With his dying breath, the mutant warns them to beware of the Great Healer. The Doctor admits that he chose to materialise the TARDIS far from Tranquil Repose because he suspected that something was not quite right. For a start, Stengos would never submit himself to something like a state of Perpetual Reinstatement. Now the question remains, who is the Great Healer and why is he creating mutations?

A prominent businesswoman, Kara, is in video conference with the Great Healer - he is requesting more money from her to continue his researches. Once the conference is over, Kara speaks to Orcini, a former Knight of the Grand Order of Oberon, and his squire, Bostock. She is employing them as assassins: their target - the Great Healer, AKA Davros. For while he has helped her to produce a protein substance vital to many of the local starving worlds, Davros is also working to rebuild his army of Daleks...