Astronaut Taylor crash lands on a distant planet ruled by apes who use a primitive race of humans for experimentation and sport. Soon Taylor finds himself among the hunted, his life in the hands of a benevolent chimpanzee scientist.
In this completely TARDIS-based story, the crew find themselves and their ship acting very strangely indeed. Blame runs high for the Ship's unusual behavior, until the Doctor realizes the TARDIS itself may be trying to warn them...
The Doctor is summoned by the mysterious and powerful White Guardian, and sent on a quest to find the six segments of the Key to Time, which, once assembled, will restore balance to the Universe. Joining the Doctor and K9 is the smart and sassy Romana, a Time Lord fresh from the Academy. Landing on the wintry planet of Ribos to locate the first segment, the TARDIS crew quickly find themselves embroiled in a little local trouble with a pair of conmen and an unstable warlord...
On the planet Alzarius in the alternate universe of E-Space, the Doctor, Romana and K9 find survivors of a crashed starliner, strange creatures lurking in the marshes and a genetic riddle which stretches back centuries.
Still trapped in E-Space, the Doctor, Romana, Adric and K9 encounter a medieval civilisation dominated by the Three Who Rule, vampires who govern from their mighty castle.
The Doctor, Romana, Adric and K9 encounter the enslaved time-sensitive Tharils, who lead them to a white void occupied only by the ruins of an old building and a spaceship - a dimension that might be the key to escaping E-Space.
After an encounter with the Master, an airline stewardess named Tegan Jovanka becomes an unwitting stowaway aboard the TARDIS as it travels to the planet Logopolis. There, the Doctor discovers that the Master's interference with the Logopolitans' advanced mathematics has unleashed a wave of entropy which threatens to consume the entire universe.
As the Doctor's trial continues, evidence is presented showing his most recent adventure, one where he faces an old adversary, Sil. As a scientist conducts his unethical experiments to prolong the life of Sil's boss Kiv, the Doctor's memories of the events begins to return and an unpleasant surprise awaits him.
The Doctor is summoned before the High Council of Time Lords to stand trial for the charges of harmful interference to the course of events during his travels which have threatened the sanctity of the universe. Indignant at these accusations, the Doctor pleads his case to the Inquisitor with the hope that she will see him as a source of hope and goodwill for existence. However, his prosecuting attorney, a sinister Time Lord known simply as the Valeyard, begins a crusade against the Doctor with the motive of framing him as a villainous renegade.
A race of giant Gastropods has taken over the planet Jaconda. Their leader, Mestor, now intends to cause an enormous explosion in order to spread his people's eggs throughout the galaxy, and he kidnaps juvenile twin geniuses from Earth to work out the necessary mathematical equations. Space fighters led by Lieutenant Hugo Lang are dispatched to get the twins back, but they come under attack and Lang is the sole survivor when his ship crashes on the asteroid Titan III. A newly regenerated Doctor and Peri become involved and help Jaconda's elderly former ruler Professor Edgeworth, who is really a Time Lord named Azmael, to defeat Mestor and free the planet's bird-like indigenous people from the gastropods' reign of terror. Azmael, however, sacrifices his life in the process.
At the Tranquil Repose mortuary, the Doctor and Peri uncover a sinister plot to create a new breed of Daleks under the supervision of the mysterious Great Healer.
The Doctor and Peri arrive on Karfel, a planet ruled by fear where the enemies of its ruler, the despotic Borad, are banished into a time tunnel known as the Timelash.
Suddenly gripped by a memory of being executed in his second incarnation, the Sixth Doctor travels to Seville to save his past self and ensure his own existence in his present.
The Doctor discovers his old enemy the Master is intent on preventing Earth's industrial revolution in 19th century England. But the Rani, a second rogue Time Lord, has plans of her own...
An alien distress call draws the Doctor and Peri to Earth, 1985, where they uncover a Cyberman plot to change the course of history.
Captured in a time corridor, the Doctor and his companions are forced to land on 20th century Earth, diverted by the Doctor's oldest enemy - the Daleks. It is here the true purpose of the time corridor becomes apparent: after ninety years of imprisonment, Davros, the ruthless creator of the Daleks, is to be liberated to assist in the resurrection of his army. Not even the Daleks foresee the poisonous threat of their creator. Indeed, who would suspect Davros of wanting to destroy his own Daleks - and why? Only the Doctor knows the truth. Will he descend to Davros' level of evil to stop him?
The Doctor and Leela must catch a killer on a vast mining ship run by robots and humans.
A three-man rocket crew are nearly done with their mission to Titan Base until a course change puts the rocket in the path of a strange cloud in space. By the time they arrive, they have come under the control of a sentient virus which threatens the galaxy. When the TARDIS picks up an emergency message, it flies into the cloud, infecting the Doctor. To save himself and others, he must undertake a dangerous journey.
The present day: just as the Fourth Doctor and Leela arrive in Fetchborough, England, Professor Fendelman prepares to experiment on a fossilized skull which science says should not exist. The skull is actually an artefact of the Fendahl, a god-like being who feeds on the life force of others. It has begun to awaken and kill. Worse yet, others seek to exploit the Fendahl's dreadful power.
Far in the distant future, Earth has become uninhabitable, forcing Mankind to colonise first Mars and then Pluto. No longer the coldest planet in the solar system, Pluto is now warmed by artificial suns. The Doctor, Leela and K9 arrive to discover the exploitation of the Megropolis people by the ruling elite, lead by the Collector. Deep in the Undercity, a small group of revolutionaries plot to overthrow the company and the Doctor is forced to fight the oppression of the people using Fire against Fire...