When the Doctor and Sarah 'go on holiday' they leave a note of explanation for a less-than-impressed Brigadier. The TARDIS arrives in an idyllic spot and the Doctor leads Sarah over a hill to a white dome. They step into an ultra modern environment. The Doctor says the Lexopterans are peace-loving and technologically advanced, but he is perplexed that his friend isn't there to greet them (even though a hundred and two years have passed since his last visit.)

They go outside and spend an hour looking for somebody to talk to. Apart from a feeling that they are being watched, neither of them sees anyone. The houses don't appear abandoned, however. They enter several buildings until they come to the Senate. In a secret room beyond the chamber they finally found the Doctor's friend Miranon. He is dead, slumped over a control panel.

They leave the chamber and return to the TARDIS for something to eat. Other than a few plants that the Doctor has never seen before, they see nothing remarkable. When they return to the chamber later, Sarah finds a book on Lexoptera's plants and inside is a piece of paper containing a biological equation. She shows it to the Doctor who tells her she has solved the mystery.

He keys in some instructions into the computer and then takes her outside. The scene is full of Lexopterans who greet him warmly. The Doctor says that the Lexopterans had discovered a way of avoiding conflict when their planet was recently invaded: they converted themselves to plants. Unfortunately, Miranon had to retain his original form to reverse the process and he was found and killed. The Doctor decides to take Sarah away on holiday.

The TARDIS is flung around erratically as the Doctor, Sarah and Harry fight to strap themselves into their seats. When they do so, they look at the writhing green on the screen. The green liquid roars away and the TARDIS settles down near a mass of flesh a mile long at least.

On the planet Hankus, in the Maston Galaxy, Jen-Ka is excited thinking about the Doctor's visit. He dips his antennae in a bowl to wash. He knocks the bowl to the floor, spilling water, and flees outside. He starts to look for Spads in the pond.

The TARDIS tumbles again through the air and lands with a crash. Unperturbed, the Doctor makes some adjustments and then he and his companions step out. Jen-Ka is delighted to see them. The Doctor, amused, says that he mis-set the controls and they landed one thousandth of their intended size. Jen-Ka accidentally ate the TARDIS with a mouthful of fruit and then spat it out, thinking it was a pip. Everyone laughs.

The TARDIS lands on Inscruta. At first the Doctor, Harry and Sarah are charmed by a familiar smell, the eight foot mushrooms and a giant red flower. Then, a cloud approaches: just as they realise it is actually a sponge it wraps itself around Sarah. It carries her away through the foliage. Harry and the Doctor give chase but are consumed by a giant plant. They escape by shouting and singing loudly. The sun sets as they reach a field of enormous cabbages. One of the Inscruta, an alien named Elkalor, ushers them into the heart of a cabbage. It is held open by a frame that prevents its leaves closing in the night. Elkalor asks the Doctor to use Galactic Sign Language to converse because everything on the planet is sensitive to noise, but the Doctor has forgotten the signs. He is, however, concerned about the tall alien's appearance.

Elkalor tells him that a disease has stricken the males of his race, causing their feathers to fall out and their skin to become transparent. At the same time their womenfolk became more boisterous and noisy and the men were driven out to hide in the cabbage patch. At the same time, they discovered that the women were harbouring a telepathic sponge in the council chambers.

The Doctor offers to help but Elkalor refuses: it is against his cultural mores to accept help from outside. Just then, Harry shows them that his own hand has become transparent. By morning, Harry has become so sensitive to sound that he fashions himself a pair of ear muffs. The male Inscruta climb down from their cabbages and wait for their women to arrive and begin their daily taunts and clamour with pots and pans. The women arrive, accompanied by a giant sponge. The Doctor recognises it as a resident of the sponge world, Femizor. He knows that it would be dangerous to use telepathy with it and so converses in its own language.

The sponge says that it has contaminated the males by accident after passing through an Oriolic dust cloud. The Doctor says that it is lying and produces a mouse-like Rhoa, the natural enemy of all sponges. He adds that Femizor sponges are amoral until they reach maturity. The sponge insists that it arrived by accident and half of it is dying due to the dust cloud. The Doctor tells it that the remedy is at hand and points to the cabbages. The sponge frees the female Inscruta from the telepathic hold and they go off to brew an elixir. The sponge is made whole, the male Inscruta grow their feathers back and the Doctor creates a molecular Speed Beam to send the sponge home. He then declares that he is on holiday and goes off to the Lake of Sighs to do some fishing.

The Doctor is fitting an Oscillating Reverberator to the TARDIS when he is called to the Brigadier. He returns to his laboratory half an hour later, annoyed at being dragged away on a false alarm. He inviters Harry and Sarah into the TARDIS to see his new gadget in action but realises at the last moment that the disruption made him assemble it back to front. The TASRDIS, in flight, comes under attack from an old sailing galleon in space.

The TARDIS lands on the deck of the ship which seems to be deserted. The Doctor goes out to investigate, warning the others not to leave the TARDIS. However, when Sarah sees the crew appear she goes out to warn the Doctor and she and Harry are captured. Their captors are space-faring race called Argamems. The Captain orders the crew to make Harry and Sarah walk the plank, adding that they will fall into the path of the laser beams that power the ship. Harry notices the Doctor return to the TARDIS. As he and Sarah prepare to die, the TARDIS materialises in front of them and they step in. The Doctor tells them that he merely sneaked in, finished his repairs and came round to pick them up.

Tamrik is proud of being the first Bremtonian to pilot a ship to another solar system. He lands on a rocky planet and prepares to release the robot. The robot is eighty five feet high, not as tall as Tamrik by any means, and its job is to make the planet suitable for his species. After six years in space, Tamrik decides to look at this new world first hand. He follows the robot out onto the volcanic surface. Then everything becomes hot and red.

The Doctor has taken Harry and Sarah to Tyrana to see some experiments that the amphibious Tyranians have completed. While there, Harry takes the opportunity to use a 3D visualiser to see some history: the Tyranians have a documentary that takes them from their origins to space flight and their meetings with the shambling giants of Bremtos.

When Tamrik died in the earthquake he had yet to switch on the robot. The radio signal that would activate it never arrived and for millions of years the robot stood, slowly being engulfed by the planet. Finally, a fragment of a message bounced into the robot's antenna and it set off on its mission.

The Doctor and his friends are interrupted by news that a giant robot is ripping up the defence building. Hurrying there, the Doctor surmises that the best way to find out about the attacker is to visit the swamp from which it apparently came. A Tyranian called Deputos flies them there in a heli-boat. They discover a huge hole in the ground and then fly into a massive space ship. Despite being left empty millions of years earlier, it is apparently exactly as it was left. The Doctor quickly works out the language of the space ship and realises that the robot is actually building an engine to fly the planet nearer to Bremtos. Deputos is astounded; the Bremtonians are a primitive people. The Doctor tells him that there was obviously a time when they weren't. He then deactivates the robot from the ship and they fly back to study it in more detail. The Doctor hints that they now have all the time in the universe.

The Doctor has been taken prisoner on Aquatica, along with Sarah Jane and Professor Vittorio Levi. The year is 3999 and the Medusians who are holding them are interested in the TARDIS. Medusia is one of three kingdoms on the planet. After various ingenious attempts to escape from their prison have failed Sarah Jane suggests the more direct route of assaulting their guard, which works. After their escape they run up the beach and sleep. They are woken by a Phyllosian, inhabitant of the second kingdom, who takes them to his home. He explains that THE Medusians are starting a war on the third kingdom, Matterdom. The Doctor is a virtual bystander in the war and after the Medusians are defeated he helps to negotiate the peace treaty. After a lengthy and educational stay they return to 1977.

The Doctor takes Sarah Jane to Zoto in the galaxy of Zaurus, circa 4000. Their holiday is spoiled by the unhealthy vegetation and absence of inhabitants. A sudden cyclone blows them miles from the TARDIS. The Doctor explains that this is a particularly unusual occurrence. By the time they return to the TARDIS it is surrounded by Zotons. They tell the Doctor that the cyclones are a recent phenomenon and have ruined their crops and homes. The Doctor strides off in the direction and discovers several reptilian Zanons operating a wind machine. The Doctor confronts the Zanons with a sharpened stick and Sarah leaps on the back of another. They flee and the Doctor uses the wind machine to blow them away, pronouncing that any survivors will flee the planet.

In the American desert UNIT have set up a laboratory where the Doctor and Sarah Jane are helping Dr Bhoul investigate a mysterious crystal, Crystal Z. Their work is interrupted when an aged prospector, possessed by aliens, storms the compound and breaks through the wall into the laboratory. The Doctor slips the crystal into his pocket and the prospector is unable to find it, though he claims it belongs to his people. He produces a Time Cube which flings the Doctor, Sarah and Bhoul back in time. They fight off a caveman, but as a mammoth attacks the Doctor discovers the Time Cube in the undergrowth, reverses the controls and sends them back to their own time. They arrive back in the desert near the unconscious prospector, now minus the alien intelligence.

While on the Doctor, Sarah and Harry are on their way to Mitra B to discuss the planet’s moral progress, the TARDIS is forced to land on Axa, a moon to the planet Torm. Rascla, the demonic-looking Master of Torm, immediately captures them. Rascla takes over the Doctor’s body with the intention of infiltrating Mitra B and release germs that will drive the Mitrans into a self-destructive frenzy of murderous hate. With the destruction of Mitra B the entire system will be vulnerable to invasion from his Tormian Toadmen. Sarah and Harry are hypnotized to complete the ruse.

The time travellers are greeted warmly by the Mitra B Committee of Moral Affairs when they arrive. Just as Rascla prepares to crush the capsule containing the germs, he freezes. All this time the Doctor has been hiding in Sarah’s sleeping psyche and has returned to reclaim his body. A brutal psychic duel ends with Rascla’s spirit is expelled into nothingness.

Later, the Doctor apologizes to Sarah for travelling in her body. She replies, “Anytime Doctor - but please ask first next time.”

The Doctor's journey to the planet of Phenolyadron is interrupted when the TARDIS is mysteriously swept across the galaxy to the planet Pergross in the year 3872. Emerging from the time ship, Sarah Jane, Harry and the Doctor are confronted with huge eyes that can spin webs and soon find themselves inside one of these creatures. There they find that there is a viewing screen which shows the creature's memories. It transpires that the creatures are the crew of a prototype time rocket from Earth, circa 3000, which landed on Pergross, mutating the humans into the Eye-Spiders. They are led by the Doctor's old friend, Xerxes Periopolos. Responding to the Spider's telepathic request the Doctor uses the TARDIS to reverse the mutation and the grateful humans return to their rocket and journey back to Earth.

After a miscalculation the Doctor lands the TARDIS in a tree, high above a steaming swamp on an alien world. When he opens the door three coppery-green creatures enter the TARDIS. Despite the alarm shown by Sarah Jane and Harry the Doctor is content to accompany these creatures through the pathways in the treetops. He speculates that they are on Diamedes and the aliens are the gentle, but dim-witted, Slodes. When a branch snaps Harry and one of the Slodes plunge towards the swamp. They are attacked by a monster but Sarah Jane's scream distracts it long enough for the Doctor to effect a rescue. After hours of walking they arrive at the Slode habitation and enter a house. The Doctor is amazed to see an old man who he recognises as Zyphos, former captain of the Tandrian fleet, who he thought died years earlier. Zyphos explains that his ship crashed on the planet, his crew died in the wreckage, the swamps or of fever and that he only survived thanks to the kindness of the Slodes. Now in his last days he yearns to see his home again and the Doctor agrees to transport him there.

The Doctor and Sarah return to UNIT HQ after a trip to the planet Dumok. Harry is pleased to see them but thinks Sarah looks ill. He later observes her behaving oddly: gazing intently at a young soldier, walking in a jerky and mechanical fashion. He follows her and sees her prepare to send a transmission into space. When he intervenes she knocks him out with a charge of electricity from her hands. He recovers in time to join the Doctor and Brigadier watching Sarah fighting with the young soldier. As they collapse to the floor two shadowy figures rise from their bodies and continue to fight. The Doctor recognises them as creatures from Dumok. The eventual victor introduces himself as Theon. He explains that a murderer from his planet was known to be hiding on Earth and he hitched a ride in Sarah's body to find him. A ship from Dumok soon arrives to take the criminal away.

The Doctor is taking Sarah and Harry to Metalupiter, a planet rich in minerals and the principle supplier of zutonium for the Psykos solar system, to meet the charming, cat-like Metalupitron robots. But as soon as they arrive they are attacked by the inhabitants.

Returning to the TARDIS the Doctor rigs up a radio transmitter to immobilize the robots. The Doctor and Harry capture a Metalupitron called Puskeet, who explains that an alien race has taken control of Metalupiter and has built reactors to fuse the planet into a giant crystal of Mitheniun, a substance used to build spaceships. A planet size crystal would take an explosion big enough to kill everything in this solar system. Puskeet then tells them to go to the centre, the reaction starts today.

The time travellers go to the center but are caught by the alien invaders. Puskeet comes to their rescue and they quickly shut down the reactors.

Japanese scientists discover evidence of a space warp. The TARDIS investigates but is sent out of control and lands on a featureless planet, not unlike a vast billiard ball. As they examine the surface a shaft opens beneath them and the Doctor, Sarah and Harry, along with the TARDIS, float gently down. They are met by some telepathic earwigs who take the trio to their leader. A scientist among them takes the Doctor on one side and explains that this is the planet Paras. The Parads live out sixteen seasons of their life cycle before entering a device called the Rectulator. He says that legend tells that it is a transporter that sends them to the twin planet of Bossgar. However, the day before his turn in the Rectulator a powerful Parad, Gresk, seized control and announced that the Parads were being used as slaves on Bossgar. The Doctor examines the Rectulator  and discovers it is a device that sends the Parads psyches to Bossgar where they live a life of peaceful speculation. It was built long before by the peaceful Xylians to help the warlike Parads. After a mental battle with Gresk the Doctor sends the Leader to Bossgar, informs the rest of the Parads of their ultimate and wonderful fate and takes Harry and Sarah Jane back to the TARDIS, confessing that their own journey home might be difficult as he has no idea where they actually are.

The Second Doctor had once befriended Swee, of the race of Guerners. They are a vegetarian species with voracious appetites and poor farming skills. As such they wander nomadically from planet to planet, decimating the vegetation and leaving behind only scrolls that give details of their stay.

Now the Fourth Doctor has landed on a new planet only to discover Swee and other Guerners outside the TARDIS, all of them (uncharacteristically) carrying weapons. On emerging from the TARDIS in what appears to be a space hangar in Houston the Doctor and Sarah are seized. Swee does not recognise the Doctor and declares himself to be called Nass. The Doctor realises that he has landed on board one of the Guerners' vast transport ships.

It transpires that the fleet is being destroyed by a Sto-Cat, fighting for the Kryptolian race. As the fleet, the Sto-Cat and the TARDIS are all that exists on this planet the Guernians assume the Doctor is controlling their attacker, but his calm manner persuades them otherwise. With some subtle psychology he discovers that the Sto-Cat is one of billions, each left on its own on a new planet, ready to subjugate any intelligent race that rises. He deactivates the Sto-Cat which Sarah is horrified to see resembles the Sphynx from Earth and allows his Guerner friends to begin their new life.

A party of Spartons land on the desert planet, Tymus, but are ill equipped to deal with the harsh environment. Most of the males are disabled by the cruel heat of the three suns and all the females die. Their scientists are desperately building new bodies for them to inhabit when the Spartrons' servants, Tymus's native inhabitants the Toregs capture the Doctor and Sarah. The Doctor is distraught when Sarah is put into a renewal machine, thinking her body parts are going to be cannibalised, but it transpires that she is merely to be the template for a whole crowd of identical females. The benign Spartrons return the real Sarah to the Doctor while he warns them that if the copies have the original's temper they are in for trouble.

The TARDIS lands on the planet Vona. The Doctor and Sarah step outside, where they are attacked by a gigantic metal insect. It captures Sarah and takes her away.

The Doctor manages to avoid the creature and find his old friend Olak, who explains the planet Vona is in the midst of a war between the two robotic species who inhabit it; the Domos and the Yeng.

Sarah has been captured by one of the Domos, and taken to their base. The Doctor and Olak manage to save her by sneaking into the base via an air vent. However, no sooner is she safe with the Doctor than the Yeng attack the base, claiming the only way to kill the Domos is to detonate their inbuilt neutron bombs.

The Doctor manages to convince them not to, explaining how the rest of the planet would be destroyed as well. The Yeng deactivate themselves and the Domos do the same, leaving the other inhabitants of the planet to begin life again.

The doctor and Sarah find they have landed in a world that was destroyed by what seems to be a chemical attack. The plants are growing back over charred remains, the buildings are blackened ruins and skeletons abound. The doctor thinks the dead were all going one way as if to escape the destruction. This leads to a manhole and the travellers climb down a ladder to a fast flowing underground river. They find a boat and the current sweeps them through a dark tunnel until they reach a section lit by blazing torches. These come in handy when they have to snatch torches to ward off an attack by savage silver creatures in the water. However, they are about to be overcome when a party of humanoids spear the creatures to death but take the couple prisoner. They are taken to the survivors' leaders, the twins Matahn and Jometh. These are old men who refuse to believe that the world above ground is springing back to life. They accuse the Doctor of being a spy for a rival clan and he and Sarah are chained up in the water to be eaten by the silver creatures. They are rescued by Barda, one of their original captors, who believed their story. They return with him to the surface while he tells of the poisonous yellow cloud that drove his ancestors underground. As he marvels at the light and space and fresh air they return to the TARDIS.

The Doctor takes Sarah to the Sigimund galaxy to watch the Aurora Arctialisis, a light display caused by three suns. They see a spaceship crash into a nearby planet but as they land to help they find other people dragging the survivors to safety. The wreckage is destroyed by Lokan robots. A survivor tells the Doctor that he and his comrades are marooned after an attack by Lokan ships. He says a ship arrives every three moons to service the Lokan robot guards. The Doctor agrees to help capture the ship. The scientists draw the robo-guards off and the Doctor penetrates the base and immobilises them. Two days later a maintenance unit lands and the scientists overpower them. The Doctor is just about to leave when one of the maintenance men wakes up. He informs the Doctor that the 'scientists' are in fact psychotic killers. The space ships are crashed and destroyed deliberately to prevent escape. When Sarah points out that the psychotics were pleasant and gentle she is told that it is the effect of the three suns and away from their influence they will return to their former ways. Before any harm can be done the Doctor calls the escaping 'scientists' back with a distress signal which they are only too happy to respond to. They are very upset to find that he lied to them and they are prisoners once more. He tries to console them by saying that they will find true freedom through their scientific work but he leaves stricken by doubt.

The TARDIS lands among a crowd of millions of humanoids, all standing in silence. As Sarah walks through them she can only hear their breathing but the Doctor can hear their thoughts: extravagant and beautiful fantasies that the dreamers do not wish to end. Suddenly a huge spaceship sweeps mere inches over the heads of the crowd. From among the silent horde a group of small children flee, telepathically warning the Doctor of 'gases. The ship vents gas and Sarah falls under its spell in her own dream of flight while the Doctor leaps onto the back of the ship. He clings on as it rises into the atmosphere and is fortunate to only weaken and drop off as it enters a vast mother ship with dozens of similar craft. The mother ship flies to the planet's moon where he finds a base containing only skeletons. From their records he finds that these people were Kendorians. As overpopulation took destructive hold over their planets the government fled to the moon and set up a fleet of gas delivery ships that would put the people into a delighted trance. An accident wiped out the moon base, leaving the automated ships to deliver the dream gas in perpetuity. The Doctor busies himself reprogramming the ships not to deliver the gas so that the Kendorians will awaken again and have some choice what to do with their own lives (though he suspects that many will wish to return to the trance). He returns to the planet on the same ship he left by, spots Sarah in the crowd and drags her to the TARDIS to revive her, all the while worrying that this is actually his own perfect fantasy.

After the Doctor has forgotten to refill the Actualising filter with Essence of Vallo the TARDIS crash lands on Planet X. It is a desert world. The Doctor and Leela encounter a group of starving three-legged octopoid children and feed them with melons. They notice that the children communicate by making hieroglyphics with the strands between their horns. Although it is impossible to understand each other the children and the time travellers become friends. Then another group of Octopoids begin shooting at them. The Doctor, Leela and Ogg, the eldest child, escape into the TARDIS. When Leela recognises that one of the symbols Ogg is making is a widely recognised peace symbol the Doctor reaches for a dictionary of signs. A conversation develops and soon the Doctor learns that Ogg and his siblings are the children of Rha, who was a scapegoat for the famine. The children are outcasts and Ogg says that his siblings will have been captured prior to execution. The Doctor's response is to find some quick-flowering seeds from Lars. He tosses a dozen out of the TARDIS and they grow into fruit-bearing plants instantly. The captors outside are too busy consuming the fruit to notice the Doctor freeing the children and taking their guard prisoner in the TARDIS. The Time Lord explains that he will provide many more seeds to feed everyone, but only if the persecution of the Children of Rha stops. After their differences are resolved the natives of Planet X head off to plant their seeds and the Doctor notices that a nearby cosmic storm has reactivated the Actualiser in the TARDIS console. As the TARDIS departs Lela notices that they have planted the seeds in the shape of a huge peace symbol.

The TARDIS responds to a distress signal and lands on a planet of dust and brown mist. The signal seems to originate from a huge skull lying in the dust but no sooner have they approached it than the ground opens around them and they are floating down on an air lift. They find themselves in a vast chamber. Seated at one end is a huge creature who the Doctor recognises as a Larkal, the same species as the skull on the surface. He introduces himself as Beshi and says that he has been on the planet for a year since his ship crashed, killing his colleague. He says that the Doctor is the first to answer his signal He asks for help on a number of points. First he wants to locate his ship, lost beneath the dust. Next he wants the Doctor to help him upgrade the myriad of plants growing in the cavern so that they can walk, talk and think. The Doctor is suspicious, the Larkal on the surface has been dead for much longer than a year. He tacitly agrees to help with some experiments - Beshi wants tissue from a warm-blooded creature - and they are carried to the laboratory. There are two plants in the lab who telepathically tell the Doctor that Beshi wants to create a plantman species that he can eat. After brief questioning the Larkal confesses that he killed and ate his colleague. The Doctor tells him to forget these plans and says he will help Beshi repair his ship so that he can go home. Beshi says he will give the Doctor two days to repair the ship but Leela is to remain as a hostage. The Doctor locates the ship, it was not lost at all, and soon works out that it was sabotaged. Plants growing nearby say that a piece was stolen by the other Larkal in an attempt to kill Beshi after a dispute over a female. They read this in the Larkal's mind but could not transmit the knowledge to the telepathy-resistant giant. With time running out the plants locate the component and the Doctor repairs the ship. Beshi blasts off for home and the Doctor and Leela return to the TARDIS for a cup of tea.

On its way to Alca Nortis the TARDIS is drawn off course and materialises on a very beautiful planet where the Doctor and Leela are greeted by a group of benign looking inhabitants. They are told that they are on Tantalogus and are given a guided tour of the largest city. They are impressed by the beauty and tranquillity. Their host, Akhemi, explains that the people are devoutly religious and leaves the Doctor in his house while he takes his family to worship. When Leela trips over a rug she accidentally opens a locked door in Akhemi's house. Inside a chamber they discover representatives of various species, wired up inside containers. Akhemi returns and holds the Doctor at gunpoint while he explains the history of the planet. He says Tantalogus is a living planet that feeds off electrical energy. The people there are not native but the dead bodies of creatures from Manya who continue to move for years after brain death. Rather than face the lumbering bodies of their relatives the Manyans have sent them to Tantalogus for generations. One who arrived, Tantalog, was not dead. After weeks of being pursued by plants and trees he realised that the planet only devoured Manyans as morsels but really needed electrical energy. Once he had built a giant generator and conductor the planet became stable and peaceful and the Tantalogans prospered. Rather than remain dead they began to use the planet's magnetic field to lure passing ships and harvested the brains of their crews. They developed a religion that worshipped death. The Doctor interrupts this monologue by kicking the weapon from Akhemi's hand and using it to destroy the generator/conductor. Instantly the planet reverts to its previous state; catching, killing and devouring Manyans. The time travellers escape into the TARDIS and escape, just in time.

There are three sentient life forms on Shem. Azula, the princess, is the rightful heir, but at her coronation Orga, ruler of the Monashem and Zig, leader of the Ragashem begin to fight. The winner will snatch the kingdom from Azula and with it The Power - an unseen life force that unites the people. The Doctor, arriving late for the coronation in the TARDIS, distracts Orga, who is killed. In the confusion Azula escapes. Zig claims the crown and immediately puts the Doctor 'on trial'. The Doctor is thrown into a pit with savage beasts and unless he reveals the secret of The Power Leela will be eaten by wild pigs called Porgs. Fortunately the Doctor is wearing an anti-gravity belt he was intending to give to Azula as a coronation present. As he rises from the pit he is attacked by Zig, a winged creature apparently. At this point Azula returns, explaining that the secret of The Power is contained in a book that she intends to share with all of the people. The Doctor uses his anti-gravity belt to knock Zig into the pit where he is killed. The coronation of Azula resumes and the book of the secret of The Power is presented to the people.

The Doctor lands the TARDIS on Pendor, inside a laboratory, hoping to catch up with some old friends. He is annoyed to discover that they are in fact on a beacon ship orbiting the planet. Intrigued by the absence of crew the Doctor begins to explore. At the landing bay he sees the three man crew preparing to change over with their replacements who are disembarking from a craft from Pendor. With the newcomers he sees a fourth man, fat with red hair, who he recognises as the criminal Skeeda, a master of subconscious manipulation. The new and old crew are clearly under his control and he commands them to wreak havoc in the busy space lanes around Pendor and to use the weather controls to ravage the planet. The Doctor realises that Skeeda is using a flashing light on a wrist device to hypnotise the men. He uses a light on a control panel and adjusts its pulsing to disrupt the hypnosis on one of the crewmen and shows him the destruction he was about to cause. The same trick awakens the rest of the crew before they annihilate the planet and for a coup de grace the Doctor mesmerises Skeeda and turns him into the crew's servant.

On Zorka the doctor and Leela are researching the medicinal properties of a rare mountain herb. They are disturbed by a skeleton asking for their help. He is Krass and he tells them his clothes and flesh have disappeared after an encounter with a mystic called Emsone. The Doctor concocts an M-Ray chamber to reverse the process. It seems to be working well when Emsone's powerful servant arrives and knocks the Doctor unconscious before kidnapping Leela. The Doctor and Klass set off in Klass's hover car to retrieve Leela from Emsone's castle. Passing over a swamp it is attacked by a giant beast but as the Doctor swerves to avoid it Klass tells him it is only a psychic illusion. At the castle they find the door open and a barrage of psychic attacks which the Doctor has to fend off before he finds Emsone. The mystic explains that he used Klass and Leela to lure the doctor to him and the illusions to wear him out because he needs to use a Time Lord's brain in a machine that will make him very rich and powerful. The Doctor and Emsone begin a fierce mental duel which causes the castle to crumble. Emsone thinks this an illusion until he is crushed to death by falling masonry. The Doctor, Krass and Leela return to their herbs which they have found make an excellent cup of tea.

The Doctor decides to go looking for life on the third planet of a binary solar system. The TARDIS lands in marsh country, a low mist covering the ground. The Doctor is attacked by a vicious creature that evades Leela's attempt to protect him but he is saved by some six-legged crocodiles. Their primitive telepathy warns him of danger nearby. He takes one back to the TARDIS and uses his Mental Image Intensifier to communicate. The crocodile warns him of lethal danger coming from a nearby volcanic crater. Upon investigation the Doctor realises the danger is carried in the mist. After fashioning some stilts the Doctor and Leela wade to the crater and find a crashed Areelian space ship. The engines are leaking deadly radiation. The doctor rigs up an explosion that awakens the volcano and destroys the ship before returning to the crocodiles to give them the good news. As the TARDIS departs Leela is still parading around the console on her stilts.

The Doctor and Romana arrive on the planet of Xethra on Academy business though neither of them seems to have any idea what they are looking for. The Doctor expects the planet to be uninhabited but they soon encounter a variety of mutated humanoids who each run away when they see the two time travellers. After pursuing the mutants they arrive at a clearing where the mutants seem to be involved in a form of non-lethal single combat. Watching this is a beautiful woman, X-Rani, who keeps her face veiled until the Doctor talks with her. She reveals herself to be telepathic.

She says that she has been sent from Ethra by the Controller. It is her duty to control the mutants. They are outcasts from her home planet and she is able to use her mind to control them and to increase the effects of their mutations. A similar programme with dissidents is happening on the sister planet Yethra. Romana reveals that Xethra and Yethra are satellite planets around Ethra. To demonstrate her powers, X-Rani gives the Doctor a third arm, albeit temporarily.

She asks the Doctor to take her back in his TARDIS so that she can confront the Controller about the programme, which she disagrees with, and to ask her why the deliveries of bavita, an essential foodstuff, have stopped. Leaving Romana to oversee the mutants, the other two return to the TARDIS.

They find Ethra to be an ordered and peaceful world where the inhabitants display high levels of beauty. The Controller's building, a large igloo shape, is well guarded but when X-Rani mutates the Doctor to look like a hideous lump of flesh the guards run away. They go inside to confront the Controller and a telepathic battle begins between the two women. The Doctor breaks the deadlock by using a palm-laser to shoot X-Rani. The Controller is pleased but wonders why he did that. The Doctor says he realised the guards were there to keep the Controller in, not X-Rani out. The Controller agree: X-Rani has usurped her power and begun a series of programmes where ugly or dissident people were banished to the moon planets. When she got wind of the Academy visit, she hid on Xethra to try to make the Controller look guilty. X-Rani's power has been lost after the Doctor shot her.

The Controller adds that bavita is not an essential foodstuff but it does make a nice tea. The Doctor goes out to gather some, thinking that Romana can look after herself for a while longer.

The Academy sends the Doctor and Roman, with K9, to investigate the uninhabited plant UX80, formerly known as Cultura until the people were wiped out in an unknown cataclysm. When they arrive, the planet is in darkness. K9 suggests that somebody is changing the frequency of light. The Doctor says that a time lord was lost on this planet and K9 says that he has detected one life form. They leave the TARDIS in radiation suits and, using a wave translator to see, soon find another time machine.

They are spoken to by Radik. He says that he failed to become a Time Lord after he was thrown out for unauthorised radiation experiments and stole a red cone TARDIS and took himself to Cultura to plot his revenge on the Time Lords. The light wavelength changes and Romana is attacked in the Darkness. By the time the Doctor adjusts the translator he finds Romana partially engulfed in a mass of gelatinous orange matter. The Doctor tries to rescue her and becomes engaged in a battle of minds. He passes out.

The battle ends while the Doctor and Romana are both unconscious. When they recover, Radik claims to have control of their minds. Roman tells the Doctor to keep him talking and, as he does so, she uses the sonic screwdriver to obliterate the renegade. Normal light returns and the pair of them decide that, now visible, the planet looks like a nice place for a holiday.

A cosmic storm leaves the TARDIS controls damaged and the Doctor is forced to land the ship on the planet Xaboi for repairs. With heavy snowfall preventing K-9 from going outside the Doctor and Romana wander out to try and find help.

They venture into a nearby cavern, whereupon they discover the remains of a group of locals. With some unease they continue, but are chased by a horrific creature further on into the cave.

They discover a tribe who have yet to develop the power of speech but despite this the Doctor persuades one of them to return with them past the now sleeping beast back to the TARDIS in order to help, but as they do so the primitive panics, attacks the beast and is killed.

The Doctor hurriedly returns to the ship to collect a stun-sensor and goes to deal with the beast but it is no good. The primitives are in danger and the gun, in stun mode, has no effect. He is forced to set the gun to kill and destroy the beast in order to save the locals, before returning to the TARDIS, pondering if he might one day return to see if they have evolved.

The Doctor lands the TARDIS smoothly in the middle of a city on Banto (despite Romana's criticism of his flying).as they walk through the city they are appalled to see people watching battle scenes on public screens and betting on the outcome. The Doctor is worried, the last time he was here the planet was peace-loving. They make their way to the home of the Doctor's friend. K9 is left on the ground floor while the other two make the long climb up the stairs to Alix's apartment.

Alix ushers them inside and warns them that Leondin has spies everywhere. Apparently, Leondin was voted into power after offering shorter working hours and longer leisure. The leisure he has provided is a series of 'galas' where he invites armies (in this case the Thralls and the Yemites) to a military parade and then uses his 'ray of wrath' to make them fight.

Almost immediately, the door bursts open and the three of them are arrested by armed men for holding an illegal meeting. On the way out, the Doctor whispers to K9 to follow at a distance. An armoured vehicle takes them to Leondin's building. Romana is locked in a cell while Leondin decides to reward the Doctor for his insolence by sending him to the battlefield to fight for the Thralls while Alix joins the Yemite army. The Doctor is given armour and weapons and feels the surge of anger as the ray is directed at the Thrall army.

Meanwhile, K9 has infiltrated Leondin's palace and freed Romana. They go to Leondin's room but it is empty. Romana switches the ray machine off only for Leondin to grab her from behind and restore the power. K9 knocks him out and Romana switches the power off.

The Doctor comes to himself, armed and bloody, in the middle of the battle. When the power is restored he fights it and turns his attention on a remote camera which he describes as 'the real enemy'. He then feels the power stop. When he is reunited with Roman (who has used her time to restore the previous government) he claims that he cut the ray of wrath when he destroyed the camera. Romana points out that she did it by pulling a lever. As the two of them squabble, K9 makes his exit.

The TARDIS lands in what the Doctor presumes to be 20th Century England. He goes off to investigate but when he does so, Romana finds herself captured by a white knight on horseback. No sooner has this happened, than a Black Knight and his warriors attack with some sort of laser weapon that they use to kill the White Knight

The Doctor meanwhile has found a castle and discovers he and his companions are not in the time he thought they were. He is held at lance-point as an intruder but before he has time to explain exactly who he is the remaining warriors of the White Knight return with Romana and K-9.

The Doctor explains that the weapon is an intervention of the forces of evil, and the balance with good must be restored. The Black Knight and his warriors soon attack but their leader is blasted by K9.

As the Doctor and his friends escape back to the TARDIS, a battle erupts which the Time Lord states will not be won by those who are ignorant…

The Doctor returns to the TARDIS after helping Zeebon become the democratic leader of the Zedons and thwarting the Electrids. He asks Roman to make a note to return for the annual celebrations of the event and then tries to dematerialise the ship. K9 reports that their dematerialisation is being prevented by a force field. The Doctor and Roman push against the force field and tumble out of the TARDIS only for the field to be reformed behind them, trapping K9 inside. One of Zeebon's assistants approaches and says that this is his doing: he wanted to speak to the Doctor privately because the Electrids have returned.

The Doctor, Romana and K9 follow Zuli to the underground laboratories where the Zedon leaves them to make their way through the passages. In a dead end tunnel they are confronted by four of the six-foot electrified worms. The three of them fall through a hidden trapdoor into a secret laboratory where they find an unhinged scientist, Zani. The Electrids slither in and Zani says that they are his pets. He says that he recreated the extinct worms with his own experiments and can control them from his terminal.

He manoeuvres one of the Electrids to approach Romana and she again falls through a trapdoor. She is amazed to be confronted by a clone of Zani. The Doctor pushes two of the worms together and they short out in a flash. The other two kill the real Zani before K9 can deactivate them. When that is done, the Doctor speaks to the clone who seems to be the opposite of the real Zani: the clone is morally good but scientifically ignorant. The Doctor and Zani use the cloning machine to give the good clone the dead Zani's mind. They then return to Zeebon to tell him the news.

After the Doctor selects a destination by inputting random coordinates, the TARDIS arrives in a massive domed room. It is full of oblong glass boxes. Each box contains a robot in the shape of a man, all wearing yellow uniforms and carrying a slim, silver weapon. They estimate that there are ten thousand robots. Behind these cases is a huge stockpile of missiles and other weapons.

They leave this huge room and find themselves in a small chapel that seems to date from a different time period. They step out into the sunshine where they see stone buildings and pleasant avenues of trees. The peace of this scene is shattered, first by a siren and then by aircraft that drop huge bombs. The people of the town flee into the chapel and the time travellers follow them underground. A man called Tallis introduces himself. He says that his people, the Valerians, are under attack from a race on the other side of the planet. The robots were built generations ago to defend them but the key to activate the robots has been lost. He is the Keeper of the Ten Thousand but he has no way of waking the army.

The bombing raid ends but as everyone emerges from the chapel they see an army of monsters in heavy armour approaching. The people are torn between pulling survivors from the wreckage and retreating. As the Doctor and Roman run to the chapel to find the TARDIS K9 finds a large crystal key in some rubble. Romana slips it into a lock and soon the army of robots is out on the streets, wiping out the enemy. Tallis thanks the Doctor for saving them but the Doctor says that the thanks should go to the robot dog.

23rd Century Earth is run-down, overpopulated and in the grip of pollution. People are fleeing to the stars and advertisers show them worlds that seem far better than the one they live on. For five million dolas (sic) a colonist can travel to Paradise 1 and start a new life in a sunny, green and technologically-advanced environment.

When the omni-directional impulse stabiliser fails on the TARDIS, the Doctor is forced to make an emergency landing on the nearest planet with level twelve technology. He and Romana step out of the ship to see if they can find anywhere that they can get parts to make some repairs. They think, at first, that they have landed on Earth but K9 points out that there are no people in the huge buildings, nor is there any pollution. The Doctor steps across to a police station but when he opens the door he finds that the building is only a facade.

K9 detects some technology and life forms ahead so the three of them walk across the miles of a huge city until they arrive at a large, low building. Roman is too footsore to continue, so she waits with K9 while the Doctor goes on alone. He walks the length of the vast building before he finds a door. As he steps inside, two armed guards grab him and hustle him through a maze of corridors. He is taken to the office of a middle-aged man called Garderon who accuses him of being a spy. The Doctor says that he has no idea where he is and insists he only came looking for parts for his ship. He is beaten over the head and knocked out.

When he wakes he is in a huge hangar and watching colonists being unloaded from cryogenic freezer units. They are attended by a ragged band of workers. Both workers and colonists are led by armed guards to a fenced compound. The Doctor is taken with them. He starts to ask a few questions.

It seems that the colonists are lured to the planet by promises of a new life but when they arrive they are treated as slave labour by Garderon and his men. The colony is actually inside a huge dome that has been built over mine shafts. The colonists work in the mines but conditions are poor and life expectancy is low. Garderon's only expense seems to be a computer programme that composes letters from the colonists to their families on Earth to maintain the pretence that they are enjoying their new life. The Doctor tells the people to organise into gangs to overpower the guards because help is on the way.

Soon, Romana and K9 trace the Doctor by homing in on the damaged omni-directional impulse stabiliser in his pocket. K9 burns through the fence to let them out. The colonists overpower the guards and the Doctor re-enters the hangar. He takes K9 and Romana with him. The robot dog knocks out the guard that they meet. The Doctor accosts Garderon and tells him that he will be sent back to Earth and tried. The facilities on the planet are, in the Doctor's opinion, perfect for a real colony.

The Doctor rejects the colonists offer to let him stay with them, gathers the parts he needs and leads Romana and K9 back to the TARDIS to make the necessary repairs.

The Doctor, Romana and K9 are in the TARDIS. The Doctor's checking the instrument readings on the central consol.

Something was shaking the TARDIS around and the three travellers were struggling to keep the thing steady. K9 took readings of the TARDIS but things were looking grim. To Romana either one of the crew of the TARDIS itself were going to break-down anytime soon if the ship didn't escape the time turbulence. K9 estimated the limit of unnatural stress at between 6.18 and 9.42 at a 100% probability rating, if conditions didn't improve soon.

The TARDIS was trapped in a cloud of anti-matter and it was slowly breaking thought the protective shielding of the time-craft. Although the TARDIS had been prepared for small anti-matter clouds, this one was a really large one, and the TARDIS was succumbing. The Doctor and Romana carried on trying to keep the TARDIS from breaking up, then, something happened. The TARDIS again jolted around violently, the crew trying to cope with the intense G-Force, K9 predicting imminent destruction. Suddenly, as Romana was pinned against the wall with the Doctor, K9 ceased functioning. The life was being drained from the pair. Then they were dead.

A black void surrounded the Doctor. Air breezed past his ears and he turned his head round and he could see a bright object. Then he could see three pyramids. They told the Doctor he was in anti-space and that they are the lords of all who exist in this universe. Then, complaining of discomfort the Doctor asks for a seat. The Doctor then found himself in the TARDIS, or a TARDIS blanketed in red light. Seated the Doctor begins to ask questions, the Pyramid beings respond. Then the Doctor says that if they were merely attacking his TARDIS, he'd be dead, so they need him for something. The beings say yes and the Doctor comments if they've been reading his mail. The Pyramids say that only Time Lords have time travel when the Doctor gets up and leaves.

The Doctor walks into a room adjacent to the control room, then asks if they want any tea whilst speaking through the doorway. After a few minutes he comes out with a tea tray with cups and sugar and a teapot. He then places them in a device, muttering to himself about different blends of tea. He shuts the door and then sets it, saying it's a mini-TARDIS that he uses to brew tea in. The Doctor then pressed a button, opened the lid, took out the tray and on it was nothing.

The Pyramids then tell the Doctor that this universe is a mirror to his and then tell him to sit down so he can be tested. Just before he is tested, the Doctor is warned by the aliens what will happen if he fails, but if he passes he and his companions can leave.

The test begins. The alien asks the Doctor "WHAT IS THE SECRET OF TIME?" The Doctor replies by saying they should know if they brought the TARDIS into their domain, but it shrugs the statement off as a rhetorical question and tells him to continue. The Doctor says he can't answer that question yet and suggests to the alien that it give him another one. The pyramids regroup and then probe into the Doctor's mind.

Suddenly the next thing the Time Lord knows is that he's been deposited onto a barren and rocky plain. The Doctor commented on the change of scene but the alien silenced him and then asked what the principal of the TARDIS' operation is. The Doctor gave one of his usual enigmatic answers and then pyramids told him to concentrate.

Then Doctor took a few steps back and said he needed to stretch his legs. The pyramids asked him where he is going, the Doctor says "For a walk", which the pyramids deem forbidden. The Doctor carried on walking whilst the alien, infuriated, tells him to stop. The Doctor taunts the gestalt being saying if it's so powerful why doesn't it stop him? The Doctor then stopped and turned back shouting "Look Out!", which the alien fell for and the Doctor ran off, much to his amusement.

However this was short lived as he stopped abruptly at a ravine, which if you looked down all you could see was a white haze. Then, the image the Doctor saw began to shimmer. The shimmering then stopped after a while and the alien chanted: "DO NOT RESIST!" The Doctor then commented that the alien was a bit limited in its powers and then said that they really do want the secret of the TARDIS. The Doctor then said that this is not a test to see if he knows, because they don't know the answer themselves, so they can not have snatched the TARDIS through the matter/anti-matter barrier and so they're still in normal space and the alien isn't an all powerful ruler.

The pyramids quickly rebutted this saying the Doctor has a vivid imagination. The Doctor asks about the other destroyed Time Lords. The alien says that was because they didn't tell it what it wanted, then saying it may have let them go, it can't remember. The Doctor then comments on the pyramids' memory and then goes on to say no Time Lord has been missing in that part of the universe for years, and that if one had strolled in there they'd have told someone about an all powerful entity. The alien flares up and declares that it is the all powerful, the one. The Doctor replies "Temper, temper!" and goes on to apologise for disturbing its Mindgames, saying it took him a while to realise it was just imagination.

Suddenly, the pyramids spun violently in a blur of shapes and colour. The Doctor then went on walking, the alien behind him pleading for the Time Lord not to go and is cut off in mid speech when the Doctor wakes up and sees Romana looking at him, shaking his shoulders. The Doctor finally woke up and asked if there was an alien around, Romana convinced he's mad. The Doctor asks if they're out of the anti-matter storm, only for K9 to tell him that the flight was smooth and uneventful. Then something dawned on the Doctor, "Ah!". Romana asked the Doctor about "an Alien" and the Doctor guesses that the alien was an observation satellite, which latched into his mind as the TARDIS passed by to continue its explorations. It created a false reality in the Doctor's mind and fooled him for moment.

Soon, after a little discussion, the Doctor decides to bring the satellite inside to take it to an advanced civilisation for it chat to there, hypothesising that the thing was lonely and in want of company. Romana however says to leave it there and that they carry on their original course. Then the Doctor asks K9, K9 saying the machine should be allowed to complete its function. The Doctor agrees and pats the tin-dog on the head.

The Doctor asks Romana if she has read 'A Midsummer Night's Dream'. She replies that she prefers 'A Hitchhiker's Guide to the Galaxy'. When she asks why, he tells her he is taking her to see the land of the midnight sun in Norway. However, before the TARDIS lands it is shaken by a disturbance and the control room glows briefly orange. K9 announces that normal flight has resumed but when they land the world is dark outside. K9 tells them that they have arrived on January 21st. The air is cold and the landscape barren. In the distance is an orange glow.

They follow this glow and find a large cavern. Within is a bright orange light that continually shifts in shape. Around it are twelve people dressed in black. The Doctor realises that they are not alone, a small boy is watching with them. The Doctor catches hold of the boy and asks who he is. The boy gives his name as Sven Larsen. He says that four of the figures in the cavern are his family. The orange entity took them because they were afraid but he says that he is safe because he does not fear the light. When the twelve figures leave the cavern, their eyes glowing like fire, the boy approaches the light but he is soon taken over and follows the others out.

The Doctor and Romana approach the shifting light and speculate about its origins, deciding that it must be alien. The thirteen people return and tell the Doctor that he will be a sacrifice; the entity will occupy his body and take human form. Romana says that the Doctor is too old for that, and the people surround her instead. The Doctor whispers a few instructions to K9 and then enters a battle of wills with the entity.

Just as he fears he has lost the mental duel, the entity diminishes in power. The thirteen people lose their purpose and Romana breaks free of them. As she runs away, K9 shoots the ceiling of the cavern and it collapses onto the light. The other people flee the cavern, wondering why they are there. The Doctor and Romana decide not to explain and make their way back to the TARDIS

The Doctor tells Romana that he’s decided to visit an old friend of his called Professor Svenson, who lives on the planet Phoenix. The TARDIS materialises inside a huge domed structure and the travellers step out, the Doctor telling Romana that robots outnumber personnel 100 to 1. Romana is uneasy at that fact. The Doctor reassures her that the robots have been programmed not to harm humans and similar.

However the complex seems deserted. The Doctor and Romana look inside a laboratory which seems deserted when the Doctor spots some bodies, one of whom is Svenson; K9 reports him to be dead. Romana looks around and notices that the lab has been smashed up when a warrior robot appears in the doorway. The three travellers flee as the robot fires upon them. The Doctor then sneaks into another room only to find it’s the way out and there are no environmental suits available. The Doctor says to risk it on the surface and to his and Romana’s relief, the air is breathable.

Meanwhile, as Romana, K9 and the Doctor run for cover, they’re being watched by a group of scientists. The two parties then meet up with each other, one of the scientists turns out to be Wooding, Svenson’s assistant. Wooding says that deputy controller Daneman is responsible for the warrior robots; she explains that Daneman has plans to conquer the galaxy with his robots. Just then, another scientist comes up to the Doctor to report that the atmosphere will only sustain life for 48 hours; he says that as he points to two collapsed men.

Suddenly, the Doctor has an idea as to how the scientists can re-take the complex. The Doctor suggests using K9 as a “wooden horse” to infiltrate the base. K9 agrees and makes his way down and enters the complex, claiming he has information on the humans. K9 meets the central computer and tells it that Daneman will get rid of it once he’s achieved his goal and persuades it to help him defeat the warrior robots. The plan involves re-programming the worker robots, which outnumber the warrior robots 20 to 1. The plan works: the warrior robots are defeated and they turn on their creator, killing him. When the Doctor, Romana and the scientists get back they find that the worker robots have elected K9 their king. The Doctor, K9 and Romana then depart in the TARDIS.

Time-Placement: The Doctor wears his Season 17 outfit. Arbitrary set between Shada and The Leisure Hive.

The Doctor takes Romana to an Inter-Galactic conference where the Vandelanian Ambassador has argued against research on sub-microscopic species. Knowing that the Time Lord delegates were called away by an unspecified emergency, he and Roman take their place. They do not have security badges but Meristan, chief of security, allows them to pass.

In the hall, Roman is pleasantly surprised to see 147 different species represented: humanoid, android, pure energy and all other possible kinds. Her pleasure is lessened when she and the Doctor are led away at gun point by a mysterious stranger. The stranger appears to be a Numese mud creature but its morphing disguise slips and reveals it to be a spy for the war-like Votons (it resembles a tree stump topped by an eyeball surrounded with worms).

The Voton tells them that it has brought them out of the conference to stop them uncovering its plan to blow up the conference and trigger a galactic war. The trigger for the bomb is the Vandelanian Ambassador's voice. When the Voton leaves to re-morph into a Numese shape, K9 frees the Time Lords. The Doctor races back to the hall and interrupts the speeches with a tirade of invective against sub-microscopic species (or 'germs' as he calls them). The Vandelanian Ambassador is so outraged that his voice goes up two octaves, allowing the Doctor to unmask the Voton spy.

Back in the TARDIS, the Doctor is basking in his victory when Romana points out a news broadcast showing that the security man, Meristan, had already found and neutralised the bomb. The Doctor decides to go back in time and attend the conference again, this time as a spectator, but Romana and K9 use their democratic powers to outvote him.

The Doctor decides to return to Earth in 2957 for the 1000 year celebration of the Space Age. He consults the coordinates he scribbled on the back of an old pawn ticket ad sends them on their way. A slight jolt before landing tells them that they have missed their target and the crew: Adric, K9 and the Doctor, find themselves in a vault filled with canisters and boxes.

Lettering on the boxes tells them that they are in the right year but on Space Station Alpha. They decide to explore anyway. When they get to a split in the corridor they go three separate ways. Adric finds himself in the Command Centre. He sees that the room is full of flashing instrument panels. The fourth wall, however, leads to a separate chamber. He steps through and the door locks behind him. A white light bathes him and he feels himself shrinking.

When Adric does not return to the rendezvous point the Doctor and K9 follow his trail. In the Command Centre, the Doctor recognises a Genesis III computer and a Composition Adjustment Teleport which can shrink or enlarge objects. The Genesis computer congratulates the Doctor on his knowledge. It adds that it was created to find places for humanity to live after the Earth became overcrowded and has managed to create colonies on single atoms. It brought the Doctor here so that it could not only colonise space but all of time, too.

Adric finds himself in a cave. He exits into a foggy jungle and follows some soldiers in blue uniforms, keeping a safe distance behind. He is then caught by the Green Army and taken to HQ for questioning. He tells them that he has come from Space Station Alpha. The soldiers mutter about a Prophecy involving Payestation Afra. They say that the war between blues and greens has waged for 800 000 years. Just then, the Blue Army attack. An officer and Adric race down to a river and swim for their lives. They pass through the mist and arrive on a sunlit bank where they are captured by the Red Army.

Genesis III tells the Doctor that it has been training armies on its single-atom planet so that it can use them to conquer the universe. The Doctor realises that time passes so quickly on such a level that if Adric has gone to this planet as Genesis says, he will have died many generations ago. Genesis says that the anniversary of 1000 years in space is the perfect date for humanity to set out and conquer all of time.

The Doctor makes a bet with Genesis that he can use the TARDIS to go back in time and save Adric. If he fails, he will put his brain and the TARDIS at the computer's disposal, but if he wins the computer must perform a task for the Doctor. He then goes to the Red City and materialises in the Hall of Justice where Adric and Daneman are being tried as spies. He ushers them into the TARDIS and then returns to the Control Room.

Back there he challenges the computer to a battle of knowledge about the universe. He links himself telepathically to the computer and for a while the two are well matched until the Doctor starts to recount the story of Puss in Boots. The computer doubts the existence of talking cats and while it is distracted the Doctor pulls the plug. He then sets about reversing the codes so that all of the people the computer has caught and miniaturised will return. He gives Daneman the task of greeting them while he and Adric set off in the TARDIS. Adric accuses the Doctor of cheating by thinking about something that doesn't exist in the universe but the Doctor says that talking cats do exist - in the imagination.

The Doctor decides to return to Earth in 2957 for the 1000 year celebration of the Space Age. He consults the coordinates he scribbled on the back of an old pawn ticket ad sends them on their way. A slight jolt before landing tells them that they have missed their target and the crew: Adric, K9 and the Doctor, find themselves in a vault filled with canisters and boxes.

Lettering on the boxes tells them that they are in the right year but on Space Station Alpha. They decide to explore anyway. When they get to a split in the corridor they go three separate ways. Adric finds himself in the Command Centre. He sees that the room is full of flashing instrument panels. The fourth wall, however, leads to a separate chamber. He steps through and the door locks behind him. A white light bathes him and he feels himself shrinking.

When Adric does not return to the rendezvous point the Doctor and K9 follow his trail. In the Command Centre, the Doctor recognises a Genesis III computer and a Composition Adjustment Teleport which can shrink or enlarge objects. The Genesis computer congratulates the Doctor on his knowledge. It adds that it was created to find places for humanity to live after the Earth became overcrowded and has managed to create colonies on single atoms. It brought the Doctor here so that it could not only colonise space but all of time, too.

Adric finds himself in a cave. He exits into a foggy jungle and follows some soldiers in blue uniforms, keeping a safe distance behind. He is then caught by the Green Army and taken to HQ for questioning. He tells them that he has come from Space Station Alpha. The soldiers mutter about a Prophecy involving Payestation Afra. They say that the war between blues and greens has waged for 800 000 years. Just then, the Blue Army attack. An officer and Adric race down to a river and swim for their lives. They pass through the mist and arrive on a sunlit bank where they are captured by the Red Army.

Genesis III tells the Doctor that it has been training armies on its single-atom planet so that it can use them to conquer the universe. The Doctor realises that time passes so quickly on such a level that if Adric has gone to this planet as Genesis says, he will have died many generations ago. Genesis says that the anniversary of 1000 years in space is the perfect date for humanity to set out and conquer all of time.

The Doctor makes a bet with Genesis that he can use the TARDIS to go back in time and save Adric. If he fails, he will put his brain and the TARDIS at the computer's disposal, but if he wins the computer must perform a task for the Doctor. He then goes to the Red City and materialises in the Hall of Justice where Adric and Daneman are being tried as spies. He ushers them into the TARDIS and then returns to the Control Room.

Back there he challenges the computer to a battle of knowledge about the universe. He links himself telepathically to the computer and for a while the two are well matched until the Doctor starts to recount the story of Puss in Boots. The computer doubts the existence of talking cats and while it is distracted the Doctor pulls the plug. He then sets about reversing the codes so that all of the people the computer has caught and miniaturised will return. He gives Daneman the task of greeting them while he and Adric set off in the TARDIS. Adric accuses the Doctor of cheating by thinking about something that doesn't exist in the universe but the Doctor says that talking cats do exist - in the imagination.

When the TARDIS lands on the planet Elystria, the Doctor is concerned. Three hundred and fifty years have passed since he was last there and things have gone badly wrong. The Doctor tells Adric and K9 that it was once called the Planet of Paradise due to its well ordered society. Now they look at the scanner and see a ruined city.

They go outside and approach the city. A man is seen running towards them, pursued by a robot. K9 drives the robot away with a few well-aimed blasts. The man thanks his saviours and takes them to one of the cellars where his people hide out. Another twenty men are in hiding. The man, Sklar, tells a surprised Doctor that it was their wise leader, Vayla, who turned on the people. The Doctor asks Sklar to lead him to Vayla's stronghold so that he can confront his old friend.

They make their way through the ruins and leave Sklar behind while they enter the robot building. Inside, they see vast laboratories where robots build more robots. The Doctor remembers that Vayla had intended to use robots to perform menial tasks. He tells Adric that he has seen all of this before: the robots gain the upper hand and take over from their masters. This is confirmed when they find the central laboratory and see a large robot in command while Vayla is imprisoned in a cell.

Adric and K9 race into the room, making as much noise as possible to distract the robot leader. Then the Doctor frees Vayla and they run out of the building, pursued by twenty robots. Just when it seems they will be overtaken, the robots malfunction and stumble about out of control. They meet Sklar and return to the cellar.

The Doctor explains that Vayla was overpowered by his creations and the men vow to look after him. The Doctor wonders why the robots malfunctioned and Adric shows him a component he stole from the control panels in the confusion; the coordination unit. They all laugh in delight.

A man called Auctor arrives at his colony village on the planet Publius, a former frontier colony from the Second Galactic Empire that survive and thrived on its own after the empire collapsed and became a blend of rustic and technological. The Doctor, Adric and K9 arrive to find the colony under the tyrannical rule of Bemar. When a worker called Stylo speaks out against her, Adric defends him. A mob converges on the time travellers. The Doctor is the only one who escapes and meets up with Kidson, musician of the spaceways. Kidson recounts how Bemar disposed of the colony leaders and seized power. He believes that she had outside help. Kidson takes the Doctor to a desolate valley to show him the Druden, an alien race using diseased human flesh as food for their sucklings.

Meanwhile back the village, the plague Auctor brought with him is sweeping the village. Bemar uses a transmitter to summon the Druden, but the Doctor re-activates K9 who destroys the transmitter, preventing the Druden from beaming to the village. Kidson uses his Strato-Cruiser to destroy the Druden once and for all.

The Doctor makes an antidote for the virus then he and his companions leave the colony to prosper again.

The instruments show that the TARDIS has landed on the planet Xiter in the year 4095 but the scanner shows only darkness. Adric and K9 follow the Doctor out into what they assume to be a large cavern but the Doctor announces that they are in the belly of a large beast. To their surprise they find that they are not alone: a Xiterian has been swallowed by the beast. He is overjoyed to see them and tells them that four others have been swallowed by the beast but he cannot find them. He begins to explain that the beast was left behind on his planet but he is interrupted by a sudden influx of gastric juices and the four of them run back into the TARDIS. The Doctor takes the TARDIS outside the beast and they look at the scanners to see a creature hundreds of feet tall.

The Xiterian tells them that the creature was a pet of some emissaries from Pflugon and only about twelve inches in length. However, after the Pflugons left without it, the beast grew to enormous size. They step out to discuss a solution. The Doctor sends Adric back into the TARDIS to fetch a trans-dimensional maxi-minimiser. He uses the device, which fails to operate at first, to reduce the creature to a size small enough to fit in a matchbox.

They say goodbye to the bewildered Xiterian and set off to Pflugon. The Doctor is worried about the minimiser's failure to work first time and his fears prove founded when the creature begins to grow rapidly, threatening to burst out of the matchbox. The Doctor makes some repairs to his device but is reluctant to use it without knowing if it will work. Bravely, Adric volunteers to be a test for it. The Doctor reduces the boy to the size of an ant and then back to normal. Satisfied that the device is working, he reduces the beast again and they carry on their journey, safe in the knowledge that the beast will not expand again.