Can the Doctor, now in his fourth incarnation, recover from his post regenerative trauma to save the Earth from Think Tank and their plot for world domination ?

The Doctor and Sarah Jane become convinced Think Tank are behind the electronic component thefts but are unable to stop them carrying out another raid.

Sarah Jane and Kettlewell infiltrate an SRS meeting to try and find out what Miss Winters is up to but there is a surprise in store.

UNIT attempt to get into the bunker to stop Miss Winters setting off the world's nuclear missiles but first they have to get past the K1.

The Doctor's attempt to give Harry a trip in the TARDIS sees the two of them and Sarah Jane arriving onboard a space station in the far future, with some rather deadly security mechanisms.

The Doctor and Harry revive the Ark's medtech, Vira, to help Sarah Jane. But when station commander Noah is revived, he becomes suspicious of the newcomers.

Knowing that Noah has been infected by the Wirrn, the Doctor persuades Vira to halt the reviving of her people, knowing it will place them in danger as well.

The Doctor tries to protect the humans still in cryogenic suspension from the Wirrn, who are determined to use Earth as their new breeding ground.

The Doctor, Sarah Jane and Harry teleport to Earth to ensure the planet is safe for the survivors on board Nerva Beacon to return and reinhabit their world. A Sontaran named Styre has captured a group of humans and is conducting experiments on them to discover the human body's weaknesses, as part of the Sontaran's goal for domination of the galaxy.

The Doctor learns that Styre has been experimenting on the Galsec crewmembers to pave the way for a Sontaran invasion of Earth and decides the only way to halt his plans is to challenge him to a duel.

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 Doctor and Harry are taken to the Kaled bunker where Davros is preparing to demonstrate the Daleks, while Sarah Jane is captured by the Thals and taken to their city as a slave worker.

The Doctor and Harry head to the Kaled city to alert the authorities to Davros' plans while Sarah Jane and Sevrin are forced to work on the completion of the Thals' rocket.

The Doctor fails to prevent the Thals from destroying the Kaled city but they don't have long to enjoy their victory before the Daleks attack.

The Doctor is forced to give Davros full details of future Dalek victories but opposition to Davros' plans is growing among the Kaleds and soon there is open rebellion.

Gharman tries to convince the Kaleds to vote against the Dalek project but Davros has a trick up his sleeve, while the Doctor works to destroy the tape recording of Dalek victory and the Thals plan an intervention of their own.

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?

The Doctor transmits Sarah Jane and Harry down to Voga to cure Sarah Jane of the Cybermat's poison but Kellman's sabotage means he is unable to bring them back.

The Cybermen force the Doctor, Stevenson and Lester to carry bombs to the centre of Voga while Sarah Jane, Harry and Tyrum decide to contact Vorus.

The Doctor, Harry and Lester try to destroy the Cybermen's relay device, while the Vogans prepare to destroy Nerva even though Sarah Jane is still on board.

Scotland, the near future. Something is smashing oil rigs off the Scottish coast, and UNIT have been called in to investigate. The Brigadier summons the Doctor to Earth to help in the investigation, but it soon becomes clear some kind of alien presence is at work...

The Zygon traps the Doctor and Sarah Jane in a decompression chamber while Harry is taken to the aliens' underwater ship.

The Doctor and the Brigadier begin to realise who the Zygon imposters among them are while Sarah Jane discovers a secret tunnel to the underwater ship.

UNIT attempt to track down the Zygon ship while Broton prepares to have the Skarasen attack London.

The Doctor and Sarah answer a distress call and find themselves on Zeta Minor, the last planet of the known universe, where a Morestran expedition has gone missing.

The Doctor realises that Zeta Minor lies on the boundary between the universes of matter and anti-matter and something on the planet won't let the Morestrans leave.

The Doctor makes a deal with the Anti-Matter Beast to return all the anti-matter to the planet but Sorenson is determined to continue his research.

The Doctor tries to convince Sorenson to sacrifice himself for the rest of the crew but Salamar's attempt to deal with the situation causes their problems to multiply.

The Doctor and Sarah are drawn off course and, instead of UNIT HQ, they arrive on the same site in 1911.

The Doctor, Sarah and Laurence try to find a way to sever Sutekh's link to the mummies while poacher Ernie Clements finds the priory surrounded by a forcefield.

The Doctor and Sarah try to destroy Sutekh's rocket but the Osiran's mental powers prove too great for them.

Sutekh forces the Doctor to transport Scarman and a mummy to Mars, where the Doctor and Sarah try to stop them destroying the Eye of Horus.

The Doctor and Sarah return to Earth in the present day to find a strangely deserted village and woods stalked by white-clad figures.

The Doctor suspects Crayford brought something to Earth in his rocket, as he and Sarah find themselves hunted by UNIT.

The Doctor is captured by Styggron and left to die in the destruction of the fake village but Sarah escapes from the disorientation chamber to try and rescue him.

The Doctor and Sarah reach Earth and try to warn the research centre about the Kraal invasion before Styggron unleashes his virus.

The storm-lashed planet Karn. Near a graveyard of crashed starships, the demented surgeon Solon hides in his castle, the last acolyte of the Time Lord despot Morbius. He only needs one final item to make his master live again... and then the Doctor and Sarah arrive...

The Doctor is captured by the Sisterhood, and Sarah Jane is blinded freeing him. The Doctor has no choice but to go back for a cure, unaware that he is leaving Sarah Jane in the hands of a treacherous Dr. Solon and the renegade Time Lord Morbius.

While the Doctor goes to confront the Sisterhood to seek a cure for Sarah Jane's blindness, Solon realizes that he must transfer Morbius' brain into a new body before it is too late.

Morbius lives once more, but as a rampaging beast. The Doctor is forced to ally with Dr. Solon to bring him to heel, but the two disagree about what should happen to Morbius.

The Antarctic, the near future. A strange seed-pod is unearthed from 20-thousand-year-old ice. The Doctor and Sarah go to investigate, but are too late to prevent the pod infecting a scientist and unleashing a threat to all animal life on Earth...

Two employees of the millionaire Harrison Chase arrive at the Antarctic base, and they will stop at nothing to get hold of the second seed-pod.

The Doctor and Sarah Jane return to England after their Antarctic ordeal and Chase tries to eliminate them, but they escape and track him down at his estate, where he is preparing to open the Krynoid pod.

The Doctor is captured by Chase, who plans to breed the stolen Krynoid pod. He is placed in an automated compost hopper and only Sarah Jane can save him... but will she make it before the Krynoid grows to fruition ?

The Krynoid grows to a monstrous size and traps the Doctor and the others in a cottage. The creature demands they turn over the Doctor, while Chase seeks to make an alliance with the alien vegetation.

The Doctor, Sarah Jane, and Scorby are trapped in the manor as a possessed Chase stalks them from within, while the gigantic Krynoid prepares to crush them from without. Worse, the alien plant is ready to germinate, spreading its seeds across England.

The Doctor and Sarah arrive in Renaissance Italy unaware that they have brought a deadly alien energy force with them.

The Mandragora energy joins forces with the secret Brotherhood of Demnos. Count Federico plots to steal the Dukedom of San Martino from his nephew, Giuliano.

Tempted by the promises of ultimate power offered by Mandragora, Hieronymous plots to eliminate the threat posed by the Doctor and uses an unwitting Sarah as his weapon.

As the leading scholars of the era assemble in the palace for the masque, Mandragora prepares to attack, intent on sending the world into a new dark age.

England, the near future. The TARDIS materialises in a quarry and Sarah is trapped under a rockfall. But what is the origin of the fossilised hand she is found gripping ? And who is the Eldrad she keeps mumbling about ?

The Doctor and Professor Watson struggle to stop first Sarah Jane and then Driscoll from obeying the strange and dangerous orders of the stone hand, which has suddenly come to life.

The energy of the reactor has returned the mysterious Eldrad to life. The Doctor agrees to take her back to Kastria. But what is waiting for them there?

The Doctor and Sarah race to save the mortally wounded Eldrad. But they find that everything is not quite as she told them.

Gallifrey, planet of the Time Lords. Summoned home by a premonition of murder, the Doctor discovers a dark conspiracy at the highest levels of Time Lord society... and his oldest enemy, who poses a threat to the existence of Gallifrey itself...

The President of the High Council has been killed and the Doctor is the prime suspect. The Time Lords are eager to dispense quick justice and the Doctor must race agains the clock to discover the truth... and an old enemy.

The Doctor has entered the computation Matrix to prove his innocence. But his opponent is prepared for him and the two engage in a mental duel to the death.

The Doctor has won his fight in the Matrix and revealed the assassin. But the Master is not defeated and sets a plan in motion that could destroy the Time Lords.

An unnamed planet, the distant future. Arriving in a place that seems oddly familiar, the Doctor finds the savage Sevateem tribe battling to free their captive god, Xoanon, from the Evil One and his Tesh servants. But can the whole situation really be the Doctor's fault?

The Sevateem launch another attack to try to free Xoanon as the Doctor tries to figure out his role in their past. But his only chance to win their trust is to face a deadly test.

The Doctor has broken through the barrier and found the Tesh. But he comes to an awful realisation about Xoanon.

The Doctor tries to fix the mad computer Xoanon. But it is determined to stop him – even if it must destroy the entire world!

An unnamed world, an unknown time. A vast mining vessel trawls a sea of mineral sand for valuable ores, the tiny human crew served by an army of humanoid robots. But as the Doctor and Leela arrive, one of the crew is found murdered... and if they didn't do it, who did?

The Doctor and Leela are suspected of murder. But the real foe is using robots to cut down the crew – and even sabotage the sand miner itself!

One of the crew is the insane Taren Capel, who is using robots to carry out the murders. The Doctor discovers that there are also others who aren't what they appear to be either.

The Doctor and the surviving humans fight for their lives against Taren Capel and his growing army of deadly robots.

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...

The Doctor and Leela investigate the strange events in Victorian London. But a mysterious masked figure lurks in the shadows.

As Li H'Sen Chang works to secure the time cabinet, Leela pursues and investigates his master – the mysterious and murderous Weng-Chiang.

The Doctor and Leela attend Li H'Sen Chang's performance, hoping to confront the magician. But his master Weng-Chiang has other plans…

The Doctor and his allies try to track down Weng-Chiang before he can activate the time cabinet and possibly destroy London.

The Doctor and Weng-Chiang have their final confrontation in the mysterious House of the Dragon -- watched by the evil duplicitous Mr. Sin.

The English channel, the 1900s AD. The TARDIS lands on barren Fang Rock, inhabited until now only by three lighthouse keepers. But what is the strange fog covering the island, and can it be connected to the falling star sighted earlier that night?

The survivors of a wrecked ship are stranded with the lighhouse crew on Fang Rock as a deadly menace slithers through the fog. Has the Beast of Fang Rock returned?

The Doctor barricades everyone in the lighthouse to protect them from the mysterious deadly creature in the fog. But it may already be inside, biding its time…

The Rutan starts picking off the surviving humans one by one as the Doctor and Leela struggle to defeat not only the alien but an entire fleet waiting to occupy Earth.

Deep space, 5000AD. An Earth supply shuttle is infected by a strange sentient space-borne virus, which quickly spreads to the crew of the refuelling station on the moon Titan. Even worse, the Doctor himself falls victim. But why is Leela immune, and what is the virus's ultimate goal?

Leela and Lowe take the Doctor to the Bi-Al Foundation for help. But how can they cure an infection of the mind?

Miniaturised clones of the Doctor and Leela are injected into his brain. But they must now fight the virus on its own level. And its servants are closing in around them.

The Nucleus, now grown to human size, is determined to spawn and take over the Galaxy. Only the Doctor and Leela can stop it.

England, the late 1970s. At Fetch Priory, Dr Fendelman's experiments with the new Time Scanner are disrupted by the mysterious death of a hiker, nearby. 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?

The mystery surrounding the strange skull deepens. Thea is slowly succumbing to its influence while the Doctor prepares to battle a creature from mythology.

While Max prepares to tap supernatural forces beyond imagining, the Doctor and Leela investigate the legend of the Fendahl.

The Fendahl is returning to life, ready to consume everything in its path. Can the Doctor find a way to kill death itself?

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...

The Doctor has been captured by the Gatherer. Leela works to free him but the Gatherer is already laying his own plans…

Now Leela is the prisoner of the Collector. He knows of the Doctor and is determined to rid himself of both of them.

The Doctor now moves to completely overthrow the Company. But the Collector has one last trump card to play.

Deep space, an unknown time. The Doctor encounters the Minyans, survivors of a race the Time Lords unwittingly obliterated early in their own history. The Minyans are searching for their race's lost gene banks, a quest which takes them to the edge of the galaxy…

After 100,000 years, the Minyans have found the long-lost P7E. But what awaits them on the ship, long buried in the core of a newborn planet?

The Minyans have, at long last, found the P7E. But a host of guards and robotic seers stand between them and the race banks.

The Minyons struggle to gain the precious race banks from the Oracle. But perhaps it is giving in a little too easily ...

Gallifrey, world of the Time Lords. The Doctor returns and claims the vacant presidency. But his behaviour is erratic and his motives mysterious.

The Doctor is made president of the Time Lords. He immediately orders K-9 to lower the planet's defences and has Leela banished to the wilderness.

The Doctor has betrayed his own people and enabled a Vardan invasion of Gallifrey. Leela joins forces with the Outsiders and prepares to strike back against the aliens.

The Doctor works to free his planet of the Vardan menace. How can he defeat an enemy who can read his very thoughts? And does their invasion conceal a greater menace?

The Sontarans have invaded Gallifrey, seeking to seize the incredible power of the Time Lords. The Doctor's first step is to cut them off from their fleet. But Kelner is helping the enemy…

The Sontarans finally invade the TARDIS itself, seeking the Great Key. The Doctor, however, has other uses for this powerful object…

The Magellanic Clouds, the planet Ribos, an unknown time. Ordered by the White Guardian to collect the pieces of the omnipotent Key to Time, The Doctor, K-9 and his new assistant Romana arrive. Collecting the first segment is not going to be easy…

Trying to obtain the first segment of the Key to Time, the Doctor and Romana are swept up in an elaborate con. The target – the homicidal Graff Vynda K.

Prisoners of the maniacal Graff Vynda K, the Doctor and Romana must break out and pursue the first segment – even as Unstoff takes it into the most dangerous place on Ribos.

Trapped in the catacombs between a mad warlord and ravenous monsters, the Doctor and Romana work desperately to obtain the segment of the Key to Time - and escape alive.

Planet Zanak, unknown time. The Doctor and Romana are seeking the planet Calufrax where the second segment waits. They are in the right place and the right time… but on the wrong planet.

The Doctor begins to investigate the mysteriously wealthy planet Zanak. Mentiads, a deranged Captain, strange omens, miraculous mines – what does it all mean? And what does it have to do with the Key to Time?

The Mentiads take the Doctor, Romana and Kimus to a reunion with K9 and Mula, where they set about trying to defeat the Captain.

The Captain and Xanxia work toward their secret goals. Both depends on the pirate planet consuming one more victim - Earth.

England, the late 1970s. The Doctor and Romana arrive in search of the third segment. But the Tracer readings are erratic and something ominous is happening with an ancient stone circle...

The quest for the Third Segment has landed the Doctor and Romana in the midst of a druidic cult centred on a stone circle. But the stones are not what they seem, and somewhere out there is a blood-thirsty Celtic goddess.

Chased by blood-thirsty stones, the Doctor must find a way to rescue Romana. What awaits him in the theoretical absurdity of hyperspace?

Facing a sentence of death from merciless justice machines, the Doctor must play for time while Romana tries to discover just who Vivian Fey really is.

Arriving on Tara, Romana locates the fourth segment of the Key to Time with ease. But getting it away proves more difficult, as she is captured by the scheming Count Grendel who wants the throne of Tara for himself.

The Doctor must employ a desperate gambit to keep the evil Grendel off the throne. And the Count has a new pawn to play - Romana.

The battle for control of Tara turns into a duel of wits between the Doctor and Grendel. But the Count shows he has more treacherous tricks up his sleeve.

Grendel plans two weddings and a funeral to cement his hold over Tara. The Doctor and K-9 race to foil him and save the Time Lady's life.

The Third Moon of Delta Magna, The Future. The Doctor and Romana arrive in search of the fifth segment and are immediately swept up in a conflict between the crew of a new refinery and the embittered natives…

The Doctor and Romana try to avoid being sacrificed to Kroll – just in time for the real monster to appear.

The massive Kroll is awake and killing anyone in its path. And the swampies are determined to appease it – by sacrificing the Doctor and Romana.

The Doctor and Romana are trapped between the monstrous Kroll and the insane refinery commander. And there is no sign of the fifth segment of the Key to Time.

Searching for the sixth segment, the Doctor and Romana land in the midst of a brutal nuclear war between the planets Atrios and Zeos.

Swept up in an apocalyptic war, the Doctor must help the Marshal defend his planet. But who or what controls the Marshal?

The Doctor meets a new enemy – the Shadow – who wants the Key to Time. And the Atrian-Zeon war is approaching an awful climax.

The Doctor is forced into a desperate gambit to prevent a massacre. But it is getting harder to tell friend from foe.

The Doctor and Romana finally venture into the Shadow's lair. The Shadow appears to hold all the cards but the Doctor has found an old friend.

The Doctor and the Shadow have their final confrontation to take control of the Key to Time. Completing it may entail an awful sacrifice. And the Black Guardian will do anything to obtain it and plunge the Universe into chaos.

Skaro, the Dalek homeworld, some time in the future. The TARDIS lands in the irradiated ruins of the old Kaled city and something is moving underneath the wasted surface of the planet…

Romana has been captured by the Daleks, the Doctor is the guest of the Movellans. The Daleks are drilling deep into Skaro for something and the Doctor has an awful suspicion about their objective…

The Daleks have awoken Davros in the heart of Skaro. Only the Doctor and the Movellans stand between them and their objective. But are the Movellans really on the Doctor's side?

Trapped between the Movellans and the Daleks, the Doctor must find a way to defeat both. Meanwhile, vast space fleets await new orders.

Paris, 1979. The Doctor and Romana are here on holiday, but something is disturbing the flow of time. Could the time travel experiments of Count Scarlioni be to blame?

Captured by the Count, the Doctor and Romana uncover an elaborate plan to steal the Mona Lisa. But there is more to Scarlioni's plans than a simple theft.

The Doctor and Romana unwrap an intricate plot involving aliens, time travel and the Mona Lisa. How is Count Scarlioni living in two times at once? And what does he want?

Scaroth is determined to go back 400 million years in time to prevent a mistake. But the Doctor must stop him – because the consequences would be disastrous.

The planet Chloris. Drawn here by a mysterious distress signal, the Doctor becomes the prisoner of the ruthless Adrasta. A strange and deadly pit awaits those who displease her.

The Doctor is in a pit with a deadly creature. And Adrasta has plans for Romana and K-9.

The Doctor has come face to face with a massive green creature. Adrasta goes into the mines to kill the monster. But everything is not as it appears…

The truth about the creature is revealed. But its imprisonment may have already set in motion a terrible revenge.

The orbit of the holiday planet, Azure, the year 2116. The starships Empress and Hecate are fused together after an accident in hyperspace. Naturally the Doctor thinks he can find a solution, but has the accident unleashed a far more deadly menace?

Two ships have collided above Azure but that may be the least of the Doctor's problems. Monsters and drug smugglers are loose on the ship. And it all seems to tie in with Tryst's electronic zoo…

The Doctor and Romana begin to uncover the truth about the strange events aboard the luxury liner Empress. They first have to separate the two ships from each other, but they've got Mandrells, drug smugglers and police chasing after them.

The Doctor finally discovers the truth about the drug smuggling ring. But the villains are still one step ahead.

Deep space, an unknown time. The TARDIS encounters a disabled Skonnon battlecruiser transporting Anethan 'tribute'. The co-pilot is determined to reach Skonnos at any cost.

Having reached Skonnos, Romana is sent with the Anethians to face the deadly Nimon.

The Doctor and Romana are trapped in the Nimon's lair. Is he really the last of his race? What are his real intentions toward Skonnos?

Romana is trapped on a ruined planet. The Nimons are launching their invasion of Skonnos. Can the Doctor stop the 'Great Journey of Life' ?

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?

Another man is found dead, strangled by the Doctor's scarf, so the Doctor is put on trial. By some of the archaic rules of law, he's made to "prove" his innocence by becoming a test subject in a new tachyon experiment with time. The result will prove his innocence or guilt, so they say.

With the Doctor suffering from the time experiment, the clandestine schemes of others start coming to light, along with the secreted purposes to which the tachyonic generator has been used.

With the saboteur and murderer revealed and arrested, peace should now be restored, but a new threat emerges - a war-monger who's both ready and eager to aggress upon other worlds with a newly manufactured warrior army.

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...

With the TARDIS occupants trapped in a chronic histeratic loop (forever reliving the same moment in time), the devious Meglos - disguised as the Doctor - gains the trust of the Tigellans along with full and private access to their power chamber.

Can Romana escape the Gaztaks ? What has become of the Dodecahedron ? What pressing appointment awaits the Doctor ?

With the Doctor about to be ritualistically sacrificed to appease the god Ti for stealing the dodecahedron, Meglos and the pirates return to Zolfa-Thura with the dodecahedron to fire up an ancient weapon and blast Tigella out of existence.

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.

Marshmen invade the Terradonian ship thanks to Romana, who seems to be in communion with them. While the ship's inhabitants flee for their lives, the Doctor discovers a crucial fact why these humanoids can never return to the planet Terradon.

Still trapped in negative E-Space, the TARDIS lands on an unnamed world to find a society sliding back into feudalism. What is the secret of the Three Who Rule? And what ancient enemy of the Time Lords is stirring again on this world...?

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."

The Doctor finds archive material in the TARDIS that tells him he's dealing with an ancient enemy of the Time Lords, a nearly indestructible king vampire who's ready to revive and reenter normal space, spreading death, once again, across the universe.

The Doctor joins the villagers' revolt against their vampire rulers, unsure how to kill the king vampire. Meanwhile Adric is first in line to join the new vampire order while Romana is laid out as a sacrificial Time Lord for the awakening king vampire and his swarm of bats.

The TARDIS is drawn into an empty white void, somewhere between universes. But they are not the only ones trapped there.

When Rorvik learns that Romana is a time sensitive, he takes her prisoner, forcing her to find a way out of the void. The Doctor attempts to discover what lies beyond the mirror.

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.

The planet Traken. The Traken union is a society living in perfect harmony, watched over by the powerful but benign Keeper. But now the Keeper is dying, and he senses a great evil within his protectorate. Can the Doctor help him discover the secret of the Melkur?

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.

With Tremas falling under suspicion, due to his association with the Doctor, a new Keeper Nominate is named. Now, with everything in place, Melkur has only a short wait before his full malevolence can unfold.

With the merciless Melkur in control of The Source, the Doctor and his allies have only a slim chance of deposing him, which also puts the peace of the Traken Union in severe jeopardy.

Deciding to repair the TARDIS' chameleon circuit, the Doctor goes to Earth to find a real police box. But an old enemy is one step ahead of him.

The Doctor, aware that his time may soon be ending, travels to the Logopolis where a series of fateful events are set in motion.

With Nyssa from Traken unexpectedly rejoining the group, Adric aids the Monitor of Logopolis in trying to save the Doctor before time runs out. The Master, at liberty to prepare, is finally ready to reveal his true target, which unknowingly sets off the biggest catastrophe of all time.

With the universe collapsing, the Doctor forms an uneasy alliance with the Master to save it. In case all does not go well, the Watcher takes the Doctor's companions to a safe place, but his plans for them don't stop there. The one hope for all lies back on Earth.