The Quartzers, calling themselves the Wardens of Time, appear after Sougo Tokiwa has collected all of the Heisei Era Ride Watches. A grand conspiracy behind the birth of the King of Time becomes ever clearer...
The TARDIS arrives on the planet Marinus on an island of glass surrounded by a sea of acid. The travellers are forced by the elderly Arbitan to retrieve four of the five operating keys to a machine called the Conscience of Marinus, of which he is the keeper. These have been hidden in different locations around the planet to prevent them falling into the hands of the evil Yartek and his Voord warriors, who plan to seize the machine and use its originally benevolent mind-influencing power for their own sinister purposes.
The Doctor, Ian, Barbara and Susan arrive in the TARDIS on board a spaceship. Their initial concern is for the ship's human crew, who are suffering from telepathic interference from the Sensorites, but Susan communicates with the Sensorites and finds the aliens fear an attack by the humans and are just defending themselves. Travelling to the Sense Sphere (the Sensorites' planet) the Doctor seeks to cure an illness to which the Sensorites and Ian have succumbed, but finds it has been caused by deliberate poisoning. The political manoeuvring of the Sensorite City Administrator poses another threat to the TARDIS crew as he seeks to discredit and implicate them.
After his girlfriend's murder, Daniel, a physics student becomes obsessed with the idea of going back in time to stop the tragedy. He lets himself be consumed by his own obsession until after years of isolation, he finds the solution. Daniel then gives up his future and returns to the past. However, he is not the same man.
The TARDIS materialises not far from Paris in 1794 — one of the bloodiest years following the French Revolution of 1789. The travellers become involved with an escape chain rescuing prisoners from the guillotine and get caught up in the machinations of an English undercover spy, James Stirling — alias Lemaitre, governor of the Conciergerie prison.
When the Doctor, Sarah Jane and Harry arrive in Scotland, having received an urgent request for assistance from the Brigadier, they discover that the mysterious force which has destroyed three oil rigs has left giant teeth marks on the wreckage. The mystery deepens, leading them to the shores of Loch Ness where they find that the legendary monster really does exist – and is the murderous tool of the Zygons, aliens intent on overpowering the planet. The Doctor, his companions and UNIT must find a way to defeat the deadly Loch Ness Monster and its controllers, but the Zygons have the terrifying power to change shape. The Doctor's life has never been in more danger, as the line between allies and enemies is tested to the very limit...
When the TARDIS malfunctions, it and its travellers land on Earth at the size of insects. They uncover a murderous plot involving a new insecticide, but how can they stop the crime in their miniaturised condition?
The TARDIS arrives in a desolate future London, where the Doctor discovers his old enemies the Daleks have taken control of Earth.
Sontaran Field Major Styre is conducting experiments on the survivors of future Earth in preparation of a full-scale Sontaran invasion of the planet. Can the Doctor defeat Styre and save the world?
The Time Lords dispatch the Doctor to the past of the planet Skaro on his deadliest adventure yet — to prevent the creation of the Daleks.
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 TARDIS crew lands in the Himalayas of Cathay in 1289, their ship badly damaged, and are picked up by Marco Polo's caravan on its way along the fabled Silk Road to see the Emperor Kublai Khan. The story concerns the Doctor and his companions' attempts to thwart the machinations of Tegana, who attempts to sabotage the caravan along its travels through the Pamir Plateau and across the treacherous Gobi Desert, and ultimately to assassinate Kublai Khan in Peking, at the height of his imperial power.
When the TARDIS lands in a quarry on Earth, Sarah unearths what appears to be a fossilised hand, buried in one-hundred-fifty-million-year-old strata. Analysis shows the hand to be silicon-based and inert, but when Sarah begins to act as if possessed, the Doctor suspects that it may still be alive...
A successful writer of children's books, Stephen Lewis is confronted with the unthinkable—he loses his only child, four-year-old Kate, in a supermarket. In one horrifying moment that replays itself over the years that follow, Stephen realises his daughter is gone. Kate's absence sets Stephen and his wife on diverging paths as both struggle with an all-consuming grief.
After the disappearance of a young scientist on a business trip, his son and wife struggle to cope, only to make a bizarre discovery years later - one that may bring him home.
Gwen has just discovered, that she's the final member of the secret time-traveling Circle of Twelve. Now she has to juggle with constant trips to the past, her relationships with Gideon and figuring out dark secrets surrounding the Circle.
When an uptight time-travelling obsessed young scientist is visited by his nihilistic future self, he's told that he needs to give up his dream of becoming the world's first time traveler, or else. But when he won't go along with the plan, it becomes a wicked battle of man versus himself – literally.
The Doctor, Jamie and Zoe return to Earth and become embroiled in the schemes of Tobias Vaughn. They meet up with an old friend, Colonel (now Brigadier) Lethbridge-Stewart, and some old enemies, the Cybermen.
The TARDIS arrives on the unnamed planet of the Gonds, who are ruled and taught in a form of self-perpetuating slavery by the alien Krotons — crystalline beings whose ship, the Dynatrope, crash-landed there thousands of years earlier after being damaged in a space battle. The Krotons are in suspended animation, in a crystalline slurry form, awaiting a time when they can be reconstituted by absorption of mental energy. Periodically, the two most brilliant Gond students are received into the Dynatrope, nominally to become "companions of the Krotons", but in truth to have their mental energy drained, after which they are killed.
The TARDIS lands in a space museum on Earth in the late 21st century, where the Second Doctor, Jamie and Zoe learn that contact has been lost between Earth and the Moon. In this era, instant travel — T-Mat — has revolutionised the Earth. Its people have lost interest in space travel. The Doctor and his companions travel to the Moon in an old-style rocket and reach the Moonbase, control centre for T-Mat, only to find a squad of Ice Warriors have commandeered the base and plan to use the T-Mat network to their advantage.