In the year 2035, convict James Cole reluctantly volunteers to be sent back in time to discover the origin of a deadly virus that wiped out nearly all of the earth's population and forced the survivors into underground communities. But when Cole is mistakenly sent to 1990 instead of 1996, he's arrested and locked up in a mental hospital. There he meets psychiatrist Dr. Kathryn Railly and the son of a famous virus expert who may hold the key to the Army of the 12 Monkeys; thought to be responsible for unleashing the killer disease.
Eighties teenager Marty McFly is accidentally sent back in time to 1955, inadvertently disrupting his parents' first meeting and attracting his mother's romantic interest. Marty must repair the damage to history by rekindling his parents' romance and - with the help of his eccentric inventor friend Doc Brown - return to 1985.
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.
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.
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...
The TARDIS materialises in Paris in the year 1572 and the Doctor decides to visit the famous apothecary Charles Preslin. Steven, meanwhile, is befriended by a group of Huguenots from the household of the Protestant Admiral de Coligny. Having rescued a young serving girl, Anne Chaplet, from some pursuing guards, the Huguenots gain their first inkling of a heinous plan being hatched at the command of the Catholic Queen Mother, Catherine de Medici.
The TARDIS has arrived on a far-distant and seemingly idyllic world. Yet the Doctor, Steven and Dodo learn it hides a terrible secret: the apparently civilised Elders maintain their advanced society by draining and transferring to themselves the life-force of the defenceless Savages.
The TARDIS arrives in London in 1966 and the First Doctor and Dodo visit the Post Office Tower. There they meet Professor Brett, whose revolutionary new computer WOTAN (Will Operating Thought ANalogue) can actually think for itself and is shortly to be linked up to other major computers around the world — a project overseen by civil servant Sir Charles Summer.
The TARDIS arrives on the coast of seventeenth century Cornwall — much to the astonishment of Polly and Ben. Pirates led by Captain Samuel Pike and his henchman Cherub are searching for a hidden treasure, while a smuggling ring masterminded by the local squire is trying to off-load contraband.
The time travellers arrive in Scotland just after the Battle of Culloden. The Second Doctor gains the trust of a small band of fleeing Jacobites by offering to tend to their wounded Laird, Colin McLaren. While Polly and the Laird's daughter, Kirsty, are away fetching water, he and the others are all captured by Redcoat troops commanded by Lieutenant Algernon Ffinch.
The TARDIS arrives on an extinct volcanic island. Before long, the travellers are captured and taken into the depths of the Earth, where they find a hidden civilisation — the lost city of Atlantis.
When the Second Doctor, Polly, Ben and Jamie visit a human colony that appears to be one big holiday camp, they think they have come across a truly happy place. Yet a shadowy presence soon makes them realise that the surface contentment is carefully controlled.
The TARDIS arrives on Earth in July, 1966, on a runway at Gatwick Airport. Polly witnesses a murder in a nearby hangar and is then kidnapped by the perpetrator, Spencer of Chameleon Tours. Ben also vanishes. The Second Doctor and Jamie are left to convince the sceptical airport Commandant there has been foul play.
The Daleks draft the Second Doctor into distilling the Human Factor. Once implanted, it will make the Dalek race invincible. Jamie's faith in the Doctor is stretched to the limit as the Doctor appears to be collaborating with the Daleks. The Doctor has a few tricks up his sleeve, but then again so might the Daleks.
Mysterious forces are at work in 1930s Tibet. The once gentle Yeti have turned savage and besieged a Buddhist monastery. The Second Doctor, Jamie and Victoria arrive expecting a friendly welcome from the abbot, but soon become ensnared in the plans of the extradimensional being known as the Great Intelligence.
The Doctor takes Ace on an initiative test to a strange Victorian old house where she is forced to confront her darkest fears.
The Doctor and Ace head for the Psychic Circus on the planet Segonax, where they meet a disparate group of performers and visitors, including a self-centred explorer named Captain Cook, his companion Mags and a biker known as Nord.
The TARDIS arrives on Earth in a new ice age. The travellers make their way into a base where scientists, commanded by Leader Clent, are using an ioniser device to combat the advance of a glacier.
The TARDIS narrowly avoids becoming engulfed in a cobwebby substance in space. It arrives in the London Underground railway system, the tunnels of which are being overrun by the web and by the Great Intelligence's robot Yeti. The time travellers learn this crisis was precipitated when Professor Travers, whom they first met in the Himalayas some thirty years earlier, accidentally caused one of the Yeti to be reactivated, opening the way for the Intelligence to invade again.