The brilliant young physicist Henrik and his fellow students develop a fusion reactor that produces endless clean energy, potentially saving Earth from environmental catastrophe. The reactor, however, is harnessed for commercial use, and the consequences for the planet and society are devastating. By the year 2064, the world has been ravaged by climate change. The UN succeeds in developing a form of time travel that can return a person's memories and personality to the moment of birth. Henrik is sent back to the past in an attempt to prevent the escalation of a catastrophe before it is too late. Something goes wrong and Henrik is forced to begin his mission from a very different starting point to the one he is used to.
A group of archaeological students become trapped in the past when they go there to retrieve their professor. The group must survive in 14th century France long enough to be rescued.
A military veteran goes on a journey into the future, where he can foresee his death and is left with questions that could save his life and those he loves.
Called in to recover evidence in the aftermath of a horrific explosion on a New Orleans ferry, Federal agent Doug Carlin gets pulled away from the scene and taken to a top-secret government lab that uses a time-shifting surveillance device to help prevent crime.
Tom Merrick gets caught up in a time-traveling conspiracy and must set the timeline right before it is irrevocably altered.
Ben is worried. Overwhelmed by the world's encroaching crises, he travels from Brandenburg to London to Kansas to the Yucatan peninsula and many places in between, to find out how to cope with social and ecological collapse.
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...
On the edge of the universe, the Doctor, Leela and K9 encounter a Minyan ship on an epic quest to find their race banks... but their people have encountered the Time Lords before...
The Doctor returns to Gallifrey, claims his rights and is inaugurated President. It soon turns out that he has led a group of aliens called Vardans to the planet to eradicate them completely. After they are destroyed, the Sontarans take their opportunity and follow them in their invasion until they are destroyed by the Doctor.
The Doctor and Romana learn the second segment of the Key to Time is on the planet Calufrax. Yet they arrive on a planet called Zanak, which has been hollowed out and fitted with hyperspace engines, allowing its insane, half-robot Captain to materialise it around smaller planets and plunder their resources.
Searching for the third segment to the Key to Time brings the Doctor and Romana to present-day Earth, where the travellers have to contend with stone circles, Druidic rituals and a not-so-mythical goddess known as the Cailleach.
The Doctor needs somewhere peaceful to recover from his traumatic regeneration. But the sanctuary of Castrovalva is not all it seems, as the Master will stop at nothing to gain his revenge over the Doctor...
The Doctor and his companions arrive on a spaceship headed for Earth, populated by natives of Earth from various different eras and commanded by the leaders of the Urbankan race. What are the Urbankans' intentions when they reach Earth?
The TARDIS lands on the idyllic jungle world of Deva Loka, which is being surveyed for possible Earth colonisation. Deva Loka is already home to a race of apparent savages, however: a mysterious people with strange powers which have mentally unbalanced the members of the expedition. To make matters worse, an ancient enemy of the natives known as the Mara is intent upon revenge, and latches onto Tegan's mind as its bridgehead to victory.
In 17th century England, the Doctor and itinerant thespian Richard Mace uncover a plot by a crew of criminal Terileptils to wipe out humanity.
The TARDIS arrives in 1925 England where the Doctor ends up playing in a local cricket match due to a case of mistaken identity. The travellers accept an invitation to a masked fancy dress ball, but events take on a more sinister tone as murders are perpetrated at the country home of their host, Lord Charles Cranleigh.
While investigating a vanishing Concorde at Heathrow Airport, the Doctor and his companions are thrown millions of years back in time, when a mysterious alien called Kalid is trying to control the ancient powers of the Xeraphin.
Omega, an ancient Time Lord made of pure anti-matter, once defeated by the Doctor, is plotting to cross over into this dimension by bonding with the Doctor. Meanwhile, the disappearance of a man in Amsterdam piques the curiosity of his cousin, Tegan, who previously left the Doctor at Heathrow Airport and now finds herself at Omega's mercy. Fearing total destruction from the collision of matter and antimatter, the Time Lords recall the Doctor to Gallifrey to undertake the only viable solution: executing him!
Tegan falls once more under the influence of the Mara and directs the TARDIS to the planet Manussa. There, the Federator's son Lon and his mother Tanha are preparing for a ceremony to celebrate the banishment of the Mara five hundred years earlier. The Mara takes control of Lon and uses him and Tegan to obtain from Ambril, the Director of Historical Research, the 'Great Crystal' - the large blue stone that originally brought it into being by focusing energy from the minds of the planet's one-time inhabitants. The Mara now plans to use the crystal during the ceremony to bring about its return to corporeal existence.