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.
Dae-ho, an investigative journalist, seeks to track down the whereabouts of his son who was abducted three years ago. With the help of a detective and a psychiatrist friend, he will retrace his memory of the incident through the use of lucid dreaming techniques.
A renegade federal agent uses a new drug to create an army of unbeatable warriors.
On a tragic night, a physicist challenges the limits of time travel to save the woman he loves, but soon discovers its inherent dangers are far greater than he expects.
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.
In the future, corporations have taken over the world and banned sex. A group of rebellious high school students devise a way to go back in time to the present day and try change history to prevent that from happening.
Barred from racing for breaking stride, a trotting horse finds a new career as a police officer's mount in Boston.
Professor Emil Keller has created a machine that can pacify even the most dangerous of criminals. But when the Doctor and Jo arrive at Stangmoor Prison for a demonstration, things start to go horribly wrong - especially when they discover that the Doctor's old enemy the Master is responsible for the machine.
A group of gold-skinned aliens known as the Axons land on Earth and offer wondrous technology in exchange for fuel. The Doctor, however, isn't fooled, uncovering the Axons' true nature and once again facing his archenemy the Master...
When the Master steals the Time Lords' secret file on the Doomsday Weapon, they grant the Doctor a temporary reprieve from his exile on Earth to deal with the crisis. He and Jo arrive on the planet Uxarieus and become enmeshed in a struggle between an agrarian colony and a powerful mining corporation.
On the eve of May Day, dark elemental forces begin to disturb the village of Devil's End as the Master summons the demon Azal: unexplained murders, a stone gargoyle come to life, and a nigh-impenetrable infernal energy dome. With the Master fully prepared to destroy the Earth, the Doctor and UNIT - aided by a benevolent practitioner of witchcraft - battle the wicked rites of a secret science wielded by an alien from another world.
As trouble brews on the space trading colony of Iceworld, the Doctor and Mel encounter their sometimes-ally Sabalom Glitz and a new friend who goes by the name "Ace".
The Doctor and Mel go for a holiday trip to Shangri-La aboard a Nostalgia Tours bus, only to get dragged into the battle against genocide of their fellow passenger Delta, a Chimeron Queen fleeing from the Bannermen who wish to make her species extinct.
The Rani has returned with another malicious scientific scheme. Taking advantage of the post-regenerative trauma the recently regenerated and unstable Doctor is going through, she hopes to achieve control of an approaching asteroid composed entirely of strange matter. Can the Doctor figure out he is being used for the Rani's evil experiment, and what is behind the door the Rani won't allow him past?