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.

Southern England, 1981. The universe has been saved, but at the cost of the fourth Doctor's life. The newly-regenerated fifth Doctor must rely on his friends to survive as the regeneration threatens to fail…

The TARDIS is plunging toward destruction. But even if the Doctor can escape, is yet another trap waiting?

The Doctor has arrived in the supposed safety of Castrovalva. But something is odd about the seemingly tranquil city…

The TARDIS crew are caught in a space-time trap. Escaping will mean a final confrontation with the Master.

Deep space, four days from Earth, 1981. The TARDIS materialises aboard a massive Urbankan starship. What is the real agenda of Monarch, master of the vessel?

The Doctor and his companions explore Monarch's vessel. But what is the secret of the ancient Earthlings aboard?

Bigon reveals Monarch's terrible plan to the Doctor. Can he act in time to save Nyssa? And which side is Adric on?

The Doctor has little time left to stop the evil Monarch. But he is losing allies — and the TARDIS is gone.

The TARDIS lands on the jungle planet Deva Loka, where an Earth expedition has been sent to study the Kinda, a tribe of primitive people. Three team members have already vanished. Are the Kinda as primitive as they seem?

Sanders meets Panna and Karuna who leave a lasting impression on him, while the Dukkha does the same on Tegan. When Hindle's breakdown begins, the Doctor and Todd are in danger.

Aris now carries the mark of the Mara and has gained voice, so Panna shows the Doctor and Todd exactly what the past, present and future hold for Deva Loka.

As the Mara finally breaks free of its dream dimension, the Kinda must do everything they can to contain it. Hindle's need to destroy everything and everyone is unstoppable.

As plague sweeps 17th century England, the Doctor discovers a more exotic threat at work - shipwrecked Terileptil convicts, intent on making the planet their own.

To rescue Tegan and Adric, captured and interrogated by the Terileptil fugitive leader, the Doctor must get past the locals under alien control and overcome Death (an android servant dressed up as The Grim Reaper).

The Doctor makes the fugitive Terileptils a rare offer they shouldn't refuse; but, though few in numbers, they have a plan in the works for the quick and complete domination of Earth and mean to see it through.

With Tegan and Richard under alien control, and the manor sealed against anyone leaving or entering, it's a question whether or not the Doctor can get to London before the Terileptils release their improved strain of black death upon the world.

The TARDIS arrives on Earth in 1925 where, due to a case of mistaken identity, the Doctor ends up playing in a local cricket match, but events take on a more sinister tone at the country home of their host Lord Cranleigh.

Ann escapes her Harlequin-clad abductor but it's The Doctor whom she accuses. Strangled bodies mount and The Doctor is arrested along with "accessories" Tegan, Nyssa and Adric. Will Lady Cranleigh's secret come out?

The TARDIS crew arrives on Earth in the 26th Century in a cave system where a military force is investigating the disappearance of a palaentological expedition.

With her crew vanishing mysteriously, Captain Briggs assumes the Doctor is the guilty party, but the traitor is closer to home… as are the Cybermen.

The Cybermen are released from their silos and are on the march, attacking Briggs's crew and ensuring that the freighter remains on course for Earth. But why?

The Doctor realises the freighter is now a huge bomb and sends it back through time where it can explode millions of years ago... but Adric is still aboard...

A Concorde loaded with passengers and crew vanishes into thin air. The still-grieving TARDIS crew arrive at Heathrow Airport in 1981 as the Doctor volunteers his services to solve the mystery.

The Doctor's TARDIS is stolen, and tracking it down reveals the existence of an alien named Kalid controlling events in the past. While the Doctor challenges Kalid's motives for being there, Tegan and Nyssa discover the source of Kalid's power - an even greater threat for the Doctor.

From within their sarcophagus, the gestalt Xeraphin are communicating through Nyssa. But their psychic energy is so powerful it may destroy her body completely.

The Master's TARDIS is repaired and the Doctor must follow him back to 20th century Heathrow, once he has rescued all the passengers and crew from both Concordes.

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.

Something seemed amiss about the Doctor's execution, so the Castellan has Commander Maxil discreetly but fully look it. Meanwhile, as the Doctor meets the anti-matter being inside the Time Lord Matrix, Tegan and her cousin's friend run afoul of a bird-like alien back on Earth.

The High Council creates a distraction so the Doctor and Nyssa can find Omega on Earth and prevent his reentry into our universe.

Tegan steers the TARDIS to the planet Manussa, without meaning to - but why? And is it a coincidence that the planet is about to celebrate the 500th anniversary of the expulsion of the insidious Mara?

The Doctor talks to Ambril and Chela to try and stop the 500th anniversary celebrations. A possessed Tegan finds herself in Dugdale's Hall of Mirrors to where she summons Lon. The Doctor and Nyssa return to the caves.

The possessed Tegan and Lon try to find the whereabouts of the Great Crystal. The Doctor finds himself in prison, with only Nyssa to try and get him out. Chela tells the Doctor tales of Dojjen.

The Doctor and the original snakedancer Dojjen work to rid the planet of the Mara.

The Doctor discovers a starship trapped in a time warp over Earth. Meanwhile, public schoolboy - and secret alien émigré, Turlough, learns he can have that which he most desires, in return for the murder of the Doctor...

The TARDIS lands on Earth six years out of date, stranding the Doctor in 1983 while leaving Tegan and Nyssa to look for him in 1977. Both parties also encounter former companion, Brigadier Lethbridge-Stewart, though curiously, he has no memory of the Doctor at all.

Mawdryn and his eternal mutants reveal the truth: they are exiles, they are in pain and need the Doctor's future 'lives', as afforded by each of his remaining regenerations.

As the Doctor's ethics are challenged and the two Brigadiers finally meet, Turlough plots with the Black Guardian to bring the Time Lord down once and for all...

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?

The Doctor's party remains divided and scattered as the immense transport docks at the Terminus space station, which turns out to be a leper colony at the exact centre of the known universe. As they find their way around and investigate, Nyssa shows signs of contracting the disease.

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?

Turlough's panic puts him aboard a pirate ship where Captain Wrack uses his presence to invite all the other captains over for dinner. She's been picking off a few of her greatest rivals in the race and now sees an opportunity to clear the field once and for all and become the clear winner.

Tegan isn't aware she been outfitted with a device to destroy Captain Striker's ship. While the detonation will merely slip the indestructible Eternals back into the realm of eternity, nothing nearly so elegant or as tidy awaits the Ephemerals aboard the ship.

In 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.

England, 1215. With the historic signing of the Magna Carta supposedly only days away, the Doctor is startled to find King John apparently intent on provoking civil war - and seemingly in two places at once...

Earth's ocean floor, 2084. With two superpowers poised on the brink of a devastating photonic war, a missile base comes under attack from the reptilian Sea Devils and Silurians, intent on eradicating the upstart human race and reclaiming the planet…

Just as the Doctor gains a tentative trust from the humans, a Silurian battle cruiser approaches. The Doctor warns Commander Vorsha to hold his fire and find out what they want, but is the level-headed commander one who'll listen?

As Vorshak's crew are cut down by Sauvix's Sea Devil Warriors, the Doctor is running out of ways to broker a peace between the opposing species.

With Silurians in control of the base, Icthar reveals his plan for a final solution to Earth's human problem, which presents the Doctor a great moral dilemma.

The sleepy English village of Little Hodcombe, 1984. The village re-enactment of the English Civil War is in full swing, but a malign alien presence intends the mock-battles to be rather more realistic than planned...

The Malus, an alien that's purely evil, needs the civil war re-enactments to become authentic so it can feed off the psychic energy of dying and embattled men and fully revive. Not if the Doctor can derail things, of course.

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…

Following the destruction of the TARDIS, the only part of it left is the hat stand. So Turlough uses it as a weapon! Plantagenet gets swallowed by the earth, and Norna and Turlough discover the Tractators.

Trying to rescue the Doctor from the Tractator's trap, Tegan lands them both in even more trouble. Turlough goes a bit mad, and reckons he knows the evil of the Tractators from old.

The Doctor tries to deal with the Tractator's cunning plan, despite Turlough's best intervention. They discover the splintered TARDIS in the tunnels beneath the planet's surface, but how will they put it together again?

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?

As the surviving station crew work to destroy the space station, Davros consolidates his power and the Daleks launch a fiendish scheme to use the Doctor against the Time Lords.

Lanzarote, 1985. Archaeologist Howard Foster raises a strange metal artefact from the sea floor. But how is it linked to the signal the TARDIS received? Why is Turlough suddenly so worried? And why is Kamelion acting so erratically?

While the Master, victim of his own attempt to improve his TCE weapon, seeks restoration through Sarn's numismaton gas, the truth of Turlough's past comes out at last, though to guarantee the safety of his brother and the Sarn people, Turlough must consider a great personal sacrifice.

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.

While the Master, victim of his own attempt to improve his TCE weapon, seeks restoration through Sarn's numismaton gas, the truth of Turlough's past comes out at last, though to guarantee the safety of his brother and the Sarn people, Turlough must consider a great personal sacrifice.

The planet Androzani Minor, the distant future. In the planet's caves war rages between government troops and the android warriors of the mysterious Sharaz Jek. But what makes spectrox, the substance they battle to control, so valuable? And how far will the Doctor go to protect his companion?

The Doctor and Peri have been rescued from the firing squad by the mysterious Sharaz Jek. But he has his own plans for them. And why are they suddenly feeling ill?

The situation on Androzani Minor is building toward a violent confrontation, and the Doctor and Peri are slowly succumbing to spectrox toxemia.

Events on Androzani reach a bloody climax. Will the Doctor and Peri survive the carnage? And at what cost?

Earth, the future. The genius Sylvest twins, child prodigies, are kidnapped by the mysterious Professor Edgeworth and taken to the planet Jaconda. But who is Edgeworth? Why does he serve the giant slug Mestor? And what is Mestor's plan?

The Doctor takes Peri to Titan 3, a desolate hunk of rock in space where he hopes to find some solitude for a while. Instead he finds the lone but unconscious survivor of a recent spaceship crash in sight of a mound-shaped complex where no formalised structure should exist.

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 and Edgeworth deduce that the real plan of Mestor, the gastropod ruler of Jaconda, will not only destroy Jaconda but lead to the devastation of other planets. Together they hope to thwart him despite his formidable ability at slipping into people's minds and controlling them.

The Doctor and Tegan meet again and remember their terrifying adventure against the Cybermen to save the Earth… and the friend they lost along the way.