The Doctor tries to recuperate within the Zero Room, leaving Nyssa, Adric and Tegan to face the Master. Then Adric is taken and the TARDIS plunges towards Event One.

The Zero Room is gone, and the Doctor’s regeneration is unstable. To help him, Tegan locates the tranquil world of Castrovalva and the TARDIS heads there.

Something is wrong with Castrovalva, but the Portreeve cannot help the Doctor identify the problem. And the Master is taunting Adric, caught in his web of power.

As recursive occlusion threatens to destroy everything and everyone in Castrovalva, the Master’s space/time trap is revealed, with Adric at its heart.

The arrival of the TARDIS is observed by three Urbankans via their manopticon devices. Intrigued, they begin dividing the Doctor’s friends, and disguising themselves as humans.

As the Doctor meets the representatives of humanity aboard the Urbankan ship, a Grecian philosopher reveals a bizarre secret about Monarch and his methods.

Panicking, Tegan accidentally pilots the TARDIS into space, while Lin Fitu betrays the Doctor and Bigon to Monarch, who demands they be beheaded as punishment.

The Doctor takes a dangerous spacewalk to rescue Tegan, while Nyssa ansd Bigon keep the Urbankans distracted and Adric decides exactly whose side he is on.

While Nyssa rests, Adric and the Doctor discover a military expedition on Deva Loka. Tegan falls asleep in the forest watched by the Kinda, but they cannot stop her dreams.

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 holds 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.

The TARDIS lands in 17th century England which is being stalked by a robotic death-like figure from behind a holographic wall. The locals seem to be under a strange mesmeric spell.

A Terileptil is living in Sir John's basement and is planning to wipe out mankind with plague rats. It decides to arrange for the Doctor and Richard Mace to be beheaded.

Nyssa and Adric and pursued by the Android, and they head to the safety of the TARDIS, while a mesmerised Tegan prepares to unleash the rats on the Doctor and Richard Mace.

Heading to London Town, the Doctor discovers more Terileptil criminals in hiding. Forced to find a way to stop them, their soliton gas generator explodes, setting London ablaze.

A murder is committed in Cranleigh Hall. The Cranleighs ask the Doctor to play cricket and then join them for a masked ball, enabling the killer to hide in plain sight.

The Doctor stands accused, despite Lady Cranleigh knowing he is innocent. What is the secret she is protecting that allows her to let an honest man go to jail.

Deadly androids are protecting a bomb buried beneath the Earth.

With her crew slowly vanishing, Briggs assumes the Doctor to be the guilty party.

The Cybermen are released from their silos and are on the march.

The Doctor realises the freighter is now a huge bomb, with one passenger still aboard...

When a Speedbird Concorde disappears back through a crack in time, the Doctor takes another Concorde to follow its trail, unaware that a mysterious conjuror, Kalid, waits for him.

After an encounter with the Plasmatons, Nyssa is possessed by strange aliens while the Doctor, joined by Professor Hayter investigates Kalid’s inner sanctum.

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 the Doctor has been chosen, during a clandestine meeting, to be used to perpetrate a terrible act. Unaware, the Doctor and Nyssa trace something odd to Amsterdam.

Commander Maxil doesn’t believe the Doctor is innocent and reckons the easiest way to stop the evil being reborn on Gallifrey would be to kill him before the bonding can occur.

President Borusa thinks the creature has been defeated but within the Matrix, the Doctor unmasks Omega and realises the threat to the matter universe is far from over.

Omega has been reborn in Amsterdam in the Doctor's form, but the transference hasn’t worked. The Doctor pursues him through the city, aware Omega is now a walking anti-matter bomb.

The Mara is returning home, to the planet Manussa, five hundred years after being exiled. And it is using Tegan's subconscious to get there in the TARDIS.

As Tegan tries to rid her mind of the Mara forever, the Doctor learns about the Little Mind’s Eye crystal, while coping with the local politics of the Federator.

As Tegan and Lon combine to give the Mara access back to reality, the Doctor locates the Great Mind’s Eye crystal but realises it is instrumental in the Mara's plan.

The Doctor and the original snakedancer Dojeen work to rid the planet of the malign Mara once and for all, but it has the whole of Manussa in its psychic grip now.

Caught in a warp ellipse, the TARDIS is drawn to a huge spacecraft orbiting Earth whereupon the Doctor is separated in space and time from Nyssa and Tegan.

At Brendon School, the Doctor enlists the help of the Brigadier. At Brendon School, Tegan enlists the help of the Brigadier. Same man, different time periods, however.

Mawdryn and his eternal mutants are awake and reveal the truth, they are exiles, they are in pain and need something only the Doctor can give them. His future lives.

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

Turlough sabotages the TARDIS causing it to fuse with the space station Terminus. Trying to separate the two, the Doctor encounters a couple of space pirates.

While the other Vanir sought out their hydromel, the curious Bor took a journey to try and solve the mystery at the heart of Terminus itself. And now he knows the secrets…

Trapped with the Lazars, Nyssa to find a way to help them, while the Doctor and Kari find the original pilot of Terminus and realise his mistake is about to be repeated...

The Garm and the pirates stop Terminus setting off a second Big Bang, while the Vanir fight between themselves for their future. Meanwhile Nyssa makes a monumental decision...

The TARDIS’s power is drained away just as the Doctor receives a dire warning from the White Guardian, and before long finds himself drawn into a strange race throgh the stars.

While Tegan has to cope with the unwelcome attention of Marriner, the Doctor realises that Striker and his officers are Eternals and that the human crew mean nothing to them.

Captain Wrack manipulates Turlough, because she is also working for the Black Guardian and during an Eternals party she places a bomb aboard Striker’s ship.

The race for the Enlightenment is over and a winner has been crowned. But Turlough must make a decision and it’s one the Doctor and Tegan cannot help him with.

At a medieval joust between Frenchman Sir Gilles and Hugh Fitzwilliam, the TARDIS appears. King John seems more curious than alarmed, as is Sir Gilles.

The Master and the Doctor fight for control over Kamelion’s mind while Turlough and Tegan make new allies in the castle in an attempt to avoid the iron maiden.

The Doctor returns to Gallifrey only to discover that a deadly game banned and derelict for centuries, has been reactivated. Soon he finds his other selves have also been summoned to assist him in tracing the culprit and tracking down the secret Rassilon.

Seabase 4 is on alert. A strange craft is approaching but the crew has been infiltrated by the enemy, so Commander Vorshak's solutions are stopped at every turn.

The Silurians and Sea Devils send the Myrka in as a spearhead to the invasion of the Seabase, whilst Nilson and Doctor Solow work to bring the entire Bloc down.

As Vorshak’s crew are cut down one by one by Sauvix's Sea Devil Warriors, the Doctor is running out of ways to broker a peace between mammal and reptile.

Lethal hexachromite gas is used against the invaders and the Doctor is despondent that no one wants to find another way to avoid so much death.

Teacher Jane Hampden is increasingly frustrated by the war games being played around the village, but the Doctor is more alarmed to find a boy transported from the 17th century.

The Malus’s influence is asserting itself all over Little Hodcombe, and the war games take an unpleasant turn. The Doctor’s best defence is in the TARDIS - but the Malus is inside.

Captain Revere is the latest person to be sucked beneath the ground on Frontios, leaving the young Plantagenet to run the colony. The Doctor’s TARDIS has also been destroyed.

Trying to discover why Frontios is being attacked from both above and below, the Doctor faces the malevolent Tractators while revolution brews in the colony.

Turlough’s race memories of the Frontios threaten to overwhelm him as the Doctor finally convinces Brazen that the threat from underground is very real.

The Doctor manipulates the Gravis into restoring the TARDIS, but still has to find a way to break the Tractators’ hold over Frontios before they wipe out all life on the surface.

Davros is held captive aboard a prison in space but the Daleks launch a rescue attempt.

As survivors of the prison station fight the invaders, Dalek agents on Earth take steps to protect the time corridor being used by the Doctor's friends.

On the planet Sarn, the truth about the god Logar is being searched for, while on Earth Peri wants a break from her stepfather. But the Master has other plans for everyone.

Kamelion has taken the TARDIS to Sarn and is trying to locate his master, while the Doctor explores the mystery of the Misos Triangle - much to Turlough's consternation.

Logar is angry and the volcano shakes with his displeasure – according to Timanov, who demands sacrifices to appease his god. Peri discovers the Master's whereabouts.

The Doctor is forced to take drastic measures against Kamelion and the Master to stop Sarn being completely destroyed by the numismaton gas that has been released.

Gunrunners are on Androzani Minor, supplying the rebellious android-builder Sharez Jek with munitions to help his attempts to return to power. But not everyone is happy about that.

Military captive Salateen tells Peri and the Doctor they are dying from spectrox tomaemia and the only cure is the milk of the queen bat, who sleeps deep below the caverns.

As Morgus continues to plot his political future on Androzani Major, Sharez Jek insanely believes Peri will fall in love with him. The Doctor is caught by the gunrunners.

Morgus is ruined, exposed as the one funding Jek’s gunrunners, and Jek himself goes on a murderous rampage. Although dying from spectrox tomaemia the Doctor saves Peri.