The English channel, the 1900s AD. The TARDIS lands on barren Fang Rock, inhabited until now only by three light-house 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?

Miniaturized 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 passing 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?

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 tohug passing 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.

Now President of Gallifrey, the Doctor puts a plan motion to apparent betray his people to an alien menace.

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 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...