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…
Earth, 1964. An accident on landing vastly reduces the TARDIS and the travellers in size. They come across a scheme run by Forester, a ruthless businessman and his misguided scientist colleague Smithers to launch a new insecticide which is capable of destroying the local ecology. Forester is prepared to commit murder to secure the success of this project - can the inch-high travellers somehow foil him?
Earth, 1964. An accident on landing has greatly reduced the TARDIS and the travellers in size. They come across a scheme run by Forester, a ruthless businessman and his misguided scientist colleague Smithers to launch a new insecticide which is capable of destroying the local ecology. Forester is prepared to commit murder to secure the success of this project, but the inch-high travellers face danger of another kind.
Sometime in the 25th century, the Doctor and his friends land on the planet Dido and happen across a spaceship (from Earth) that has crash-landed. Its two occupants - a man named Bennett and a young girl called Vicki - are living in fear of a creature called Koquillion, a native of Dido possibly responsible for murdering other members from the spaceship. However, the Doctor realises after a while that Koquillion is in fact Bennett in disguise; it was Bennett who killed the others so as to conceal an earlier murder that he had performed on ship. In a confrontation with Dido humanoid inhabitants Bennett dies as he falls from a cliff. Not wishing the girl Vicki to be alone, the Doctor takes her with him in the TARDIS as a new companion.
Space Security agent Marc Cory visits the planet Kembel to investigate rumours of Dalek activity in the area. However, his ship is shot down and his crewmates are poisoned by the thorns of Varga plants, genetically engineered carnivores which transform their unlucky victims into Vargas as well. Despite these dangers, Cory discovers that the Daleks have formed an alliance with several other alien species, intending to launch a war against Earth. He makes a tape of his discoveries -- but is exterminated before he can get word to his superiors...
The TARDIS arrives in Tombstone, Arizona in 1891. Where the Doctor is looking for a dentist when he has a toothache, where The Doctor finds the local dentist is the famous Doc Holliday who is in a feud with The Clanton Brothers and their hired gunfighter Johnny Ringo, whilst local sheriff Wyatt Earp is trying to keep the peace. The Doctor, Steven and Dodo find themselves joining forces with The Clanton Brothers and Sheriff Wyatt Earp.
London 1966 and the Doctor and Dodo, on a visit to the Post Office Tower, meet Professor Brett whose new computer WOTAN can actually think for itself and is soon to be networked with other computers around the world. However, WOTAN believes that humans are inferior to machines and should, therefore, be ruled by them. Exerting a hypnotic influence, WOTAN arranges for the construction of War Machines - heavily-armed, self-contained mobile computers - with which to take over the world. These prove more than a match for the Army, but the Doctor is able to capture one of them, which he then re-programs to destroy WOTAN. When the crisis is over, Dodo chooses to remain in London; Ben and Polly, however, inadvertently become the Doctor's new companions when they enter the TARDIS to return his lost key.
The TARDIS materialises in 21st-century Earth, where the Doctor discovers that he's the exact double of the philanthropic scientist Salamander. Salamander has ended world hunger and has been supplying humanitarian aid to parts of the world which have recently suffered inexplicable seismic activity. However, his former associate, Giles Kent, claims that Salamander is in fact a power-crazed maniac who's slowly replacing the authorities of Earth with lackeys under his thumb. The Doctor isn't so sure, and agrees to impersonate Salamander and find out the truth only if Jamie and Victoria can prove to his satisfaction that Salamander is indeed an evil man. However, Jamie and Victoria soon find themselves in over their heads – and even before he has a chance to act, the Doctor is already being hunted by Donald Bruce, the suspicious chief of World Zone security.
The TARDIS lands on the peaceful planet of Dulkis. There, the Doctor, Jamie and Zoe discover that the ruthless Dominators have arrived and are enslaving the inhabitants with their deadly robots, the Quarks.The Doctor and his crew must prevent the destruction of the planet and help the Dulcians fight back.
The TARDIS lands in London where the Doctor, Jamie and Zoe agree to help find Isobel Watkins' missing uncle. Searching for Professor Watkins at his last place of work, a multinational electronics supplier, he meets the company's managing director. He's not what he seems - and possesses alien technology in his office.
The TARDIS lands in what appears to be the front-line trenches at the height of battle in war-torn France, right in the middle of World War I. Everyone they meet are convinced that the crew are spying and it doesn't take long for the crew to be on the run, but not before breaking the hypnotic conditioning of Carstairs and Lady Jennifer. Having escaped one war-zone they find themselves in another - Roman occupied Britain of some 2,000 years ago, then on to the American Civil War. The situation worstens when the Doctor suspects one of his own people, a Time Lord, to be behind the War Games working for a race of aliens trying to run the wars to their conclusions under controlled conditions to find a super-army or fighters. The Doctor is faced with an impossible situation - not only does the War Lords' control over hundreds of thousands of fighters need to be removed, but the soldiers have to be returned to their natural habitats. He conceeds defeat at the task, knowing that the TARDIS is not equipped for the task. He sends an SOS, calling in his own people even though it is revealed that he is 'on the run' from them for the theft of a TARDIS and for meddling... The Doctor is caught and faces trial.
The planet Peladon, some time in the future. The Doctor and Sarah arrive on the planet Peladon 50 years after "The Curse of Peladon" They find King Peladon's daughter, Queen Thalira has inherited the throne. The Galactic Federation is at war with Galaxy Five and needs the mineral Trisilicate in order to bring about an end to the war. It seems the Ghost of Aggedor has been sighted and is blamed for killing of miners, which hampers the acquisition of the much needed Trisilicate.
Deep space, the distant future: following Earth's devastation by solar flares, the survivors of mankind are in cryogenic suspension aboard the Nerva Beacon space station. The Doctor, Sarah and Harry arrive on board to find the station suffering from mysterious damage and some manner of creature at large…
The planet Skaro, the distant past. The Time Lords divert the Doctor, Sarah Jane and Harry to this war-torn world, and give the Doctor a mission: the evil of the Daleks is about to be born here, and the Doctor is to try to ensure they evolve into less lethally aggressive beings - or, failing that, to avert their creation altogether. But has even the Doctor the right to commit genocide?
The orbit of Jupiter, the 25th century. Arriving back on the Nerva Beacon much earlier in history, the Doctor and his friends discover the satellite beset by space plague while its crew struggles to keep space traffic away from Voga, the newest moon of Jupiter. But what is the connection between Voga, the plague, and some old enemies of the Doctor?
Deep space, the distant future: following Earth's devastation by solar flares, the survivors of mankind are in cryogenic suspension aboard the Nerva Beacon space station. The Doctor, Sarah and Harry arrive on board and are greeted with suspicion by the awakening survivors… just as the menace of the insectoid Wirrn becomes apparent.
London, the 1890s. As magician Li H'Sen Chang captivates audiences, a spate of disappearances amongst young women goes largely unnoticed. But almost upon their arrival, the Doctor and Leela find themselves confronting the feared Tong of the Black Scorpion, and a menace from another time. And there's something fishy in the sewers, too...
England, the late 1970s. At Fetch Priory, Dr Fendelman's experiments with the new Time Scanner are disrupted by the mysterious death nearby of a hiker. Then there's the mysterious skull, also being used as part of his work--a skull that seems to predate the evolution of mankind. What is the true role of the Fendahl in humanity's evolution?
Pluto, the distant future. The planet has been terraformed and is now orbited by artificial suns, provided by the rapacious company who ruthlessly exploit the relocated human workforce. The Doctor, Leela, and K9 arrive and befriend a luckless drone worker, but they must flee with him to the dark undercity...
Gallifrey, world of the Time Lords. The Doctor has claimed the presidency of the planet (on a technicality, following events in the previous season's The Deadly Assassin) and his behaviour is even more eccentric than usual in other ways, too: he refuses to speak to Leela and seems only to trust K9. But has he really betrayed Gallifrey to a Vardan invasion force? And is there a further power behind the Vardans?
The planet Argolis, around the year 2290. The Argolins live in a huge shielded city, protected from the irradiated wasteland outside. The planet's survival depends on the tourists their Leisure Hive attracts. But a series of horrific deaths seems to jeopardise that future - can the Doctor and Romana find a solution?
The desert planet Zolpha-Thura, the 1980s. Giant intelligent megalomaniac cactus Meglos is planning to conquer the galaxy but first it needs the dodecahedron, a powerful energy source currently on the planet Tigella. To get it back Meglos recruits a band of galactic mercenaries and hatches a cunning scheme requiring it to impersonate the Doctor...
Deep space, an unknown time - on course for Gallifrey, the TARDIS passes through a strange disruption. When they materialise, the scanner shows the Time Lord homeworld... but the travellers have passed into the negative pocket universe of E-Space and are in fact on the planet Alzarius, where evolution works very differently...
As the humanoid community takes refuge in their crashed spaceship, venomous marsh spiders begin to hatch from the local fruit while bestial marshmen emerge from the waters to walk the land. It is quite apparent that the marshmen desire entry into the spaceship. Meanwhile, as a curious marshchild shadows the Doctor, a group of teen rebels decides to take over the TARDIS.
Infection from a spider bite causes Romana's personality to change. Meanwhile the Doctor, after discovering that the spaceship society is in a perpetual state of repair and upgrade, has morality issues with the ship's leading scientist who readies himself to perform gruesome experiments on the live marshchild while it's fully conscious.
The Doctor and Romana are escorted to the tower to meet the royal leaders, hoping they can find answers to why this society evolves backwards. The Doctor recognizes the tower as an old Earth spaceship, and further finds that the old fuel tanks, far from empty, are full - but with blood. Meanwhile, Councilor Aukon senses intelligence in Adric and selects him to be the their first "Chosen One."
While Biroc leads the Doctor to a view of the Tharil's lordly past, Romana learns more about the damaged freighter and the coldheartedness of its crew. Meanwhile Commander Rorvik, confounded by the time mirror inside the universal center gateway, ignores evidence that it's no simple mirror and decides to blast it, imperiling the lives of everyone.
The Doctor deduces that the freighter is a slave ship loaded up with Tharils to be sold as time machine components, but the immense weight of Rorvik's damaged ship, designed to contain the Tharils, is now collapsing the fragile void of the micro-universe in which they're all stuck, pulling everything inside ever closer.
Tremas claims consular privilege to protect the Doctor and Adric from execution, though it binds his fate to theirs if they're found guilty of murder. Melkur strengthens his hold over Kassia while Seron decides to have rapport with The Keeper to learn truth, and Adric finds evidence of another TARDIS in the area.
On Gallifrey, someone on the high council is perpetrating a treasonous act - transmitting the Doctor's bio-extract from the space/time matrix to an anti-matter being. On Earth, two English lads spend their last night in Amsterdam sleeping in a crypt where they're attacked by an alien creature under the same anti-matter being's control.
With an anti-matter being trying to enter the universe through the Doctor, risking the destruction of everything, there is only one clear course of action for the High Council of Time Lords to take: execute the Doctor. Meanwhile, Tegan arrives in Amsterdam and hears about what's become of her cousin from his unscathed friend.
Deep space, some time in the future. Still following the Black Guardian's orders, Turlough sabotages the TARDIS, forcing an emergency fusion with an apparently deserted starship. But the ship is headed for the notorious plague colony, Terminus. Surrounded by plague victims and space pirates, is the Doctor too preoccupied to notice the greatest threat of all - a threat connected to the position of Terminus at the exact centre of the universe?
Since the Doctor's party represents neither lazars nor handlers, they're presumed to be investigators, which is enough to spark the disgruntled Valgard into challenging Eirak over leadership of the handlers. Meanwhile, as the giant, dog-like Garm takes a terrified Nyssa off for "treatment," Bor returns from the forbidden zone with interesting news about the ship.
In attempting to reopen a doorway into the TARDIS, Turlough activates Terminus' automated fuel-jettisoning sequence. The first time this sequence was engaged, it flung its first of two massive loads of unstable fuel into the distant past, producing the Big Bang that created the universe. This second sequence - if the Doctor can't find a way to shut it down - will release a second massive load, the explosion of which will entirely negate the effects of the first.
After receiving a warning from the White Guardian, the Doctor initially believes the TARDIS has landed aboard an Edwardian clipper ship - but all is not as it seems. While the time travellers are caught up in the omnipotent Eternals' race for the ultimate prize, the Black Guardian's scheme to destroy the Doctor enters the end-game - but which side is Turlough a pawn of?
Captain Striker and his officers reveal themselves to be Eternals, mind-reading creatures who live outside of time and who require Ephemerals (humans and other "time dwellers") to relieve them of their emptiness. They race against other Eternals for the grand prize of Enlightenment, by which to grant their deepest wishes. That can't be good for the universe, but how can the Doctor strategise against beings adept at reading his every thought?
England, 1215. At the castle of Ranulf Fitzwilliam, son Hugh is jousting on a matter of honor against Sir Gillis Estram, the champion of King John, when the TARDIS appears. The Doctor, Turlough and Tegan are immediately hailed as demons and welcomed warmly by the King. Something is wrong with this picture, observes the Doctor.
Gallifrey, planet of the Time Lords. The Death Zone, where the ancient Gallifreyans once staged gladiatorial games between alien races from throughout the universe, has been reactivated. No less than three of the Doctor's former incarnations and several of his companions are brought here. But why? And who is the Player in the Game of Rassilon?
The planet Frontios, in the distant future. Following Earth's destruction, a tiny colony struggles to eke out a life on this desolate world. But where do the bombardments that threaten them originate from? Little does the Doctor suspect that somewhere nearby lurks a power capable of ripping even the TARDIS apart…
London's Docklands, 1984. Why are uniformed policemen gunning down strangely-dressed vagrants in broad daylight? A prison ship in the far future - who is the sole prisoner aboard the craft? And why are these two locations linked by the time corridor the TARDIS has been sucked into? Lytton's men revive Davros as the Doctor fights off the Dalek in the warehouse. But alliances are shifting with each passing moment. Can anyone be trusted?
Sarn prophesy foretells of an outsider who will come to aid the people. It's a role the Master is more than delighted to fill, which finally presents Timanov, the Sarn religious leader, the unbridled support he's sought in his campaign to cull the faithless from among his people. Turlough's secret past, however, is somehow intricately involved in all this, and the reluctance of its disclosure is enough to threaten all friendly ties with the Doctor.
The Doctor arrives on Jaconda, once lush and green, to find it completely devastated by giant gastropods. Old legends about the planet's half-human/half-slugs weren't just myths after all. With or without help from the Doctor and his unpredictable mood swings, Lt. Lang is up for rescuing the twins, who are finally informed of the grand purpose they've been brought to Jaconda to accomplish.
The Doctor is taken "out of time" by the Time Lords and made to face an inquiry into his meddling in the affairs of others, overseen by the Inquisitor. The prosecutor, the Valeyard, soon has the proceedings upgraded to a trial for the Doctor's life. Evidence takes the form of recordings of the Doctor's recent adventures, beginning with his visit to the mysterious world of Ravalox and an encounter with Andromedan space pirates...
The solstice nears, making it time for the Rani to bring her plans into fruition. The Doctor's sympathies for Beyus, ruler of the Lykertyans, are rather qualified. Beyus' heart is for his people yet something prompts him to collaborate fully in helping the Rani reach all her objectives. The answer, he's told, lies within the Center of Leisure.
Wales, 1959. A top-secret US satellite has mysteriously gone missing. This could have something to do with the arrival of a party of alien tourists en route to Disneyland, amongst their number Mel and the Doctor, and the Queen of the Chimerons - who's fleeing the Bannermen and their genocidal leader Gavrok...
San Francisco, 1999. Returning home to Gallifrey with the remains of the Master, the TARDIS is forced off course, landing the Doctor in the middle of a street gang's gun fight in San Francisco. Critically wounded in the shoot out, the Doctor regenerates to save his own life. Meanwhile, the Master has taken possession of another new body. As the clock counts down to the start of the new millennium, the Doctor has to stop the Master destroying all life on Earth. The stage is set for what could be the final battle between these arch-enemies…