The Doctor and Mel visit Paradise Towers, a residential complex that promises a peaceful life to its residents. However, the establishment is far from what its name suggests: A conflict persists among the Kangs, humanesque multicolour beings who gather in opposing gangs based on which colour of the rainbow they bear; killer cleaning robots prowl the halls, and a secret in the complex's basement poses the greatest threat of all.

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.

London, 1963: The Doctor returns to the place where it all began — alongside his latest companion, Ace, with unfinished business. Not for the first time, unusual events are unfolding at Coal Hill School. At 76 Totter's Lane, the Doctor discovers that his oldest foes — the Daleks — are on the trail of stolen Time Lord technology that he left on Earth long ago. The Daleks are planning to perfect their own time-travel capability, in order to unleash themselves across the whole of time and space.

The TARDIS arrives on the planet Terra Alpha, where the Seventh Doctor and Ace discover a society in which sadness is against the law - a law enforced zealously by the brightly uniformed Happiness Patrol. The planet is ruled by Helen A with the aid of her companion, Joseph C, and her carnivorous pet Stigorax, Fifi.

The arrival of a mysterious comet heralds impending danger from enemies both old and new. As Ace helps the Doctor defend Earth, she is confronted with a dangerous question..."Doctor Who?"

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.

Knights from a parallel universe arrive on Earth to find the legendary sword Excalibur. Only the Doctor and Ace, with the assistance of Brigadier Lethbridge-Stewart, can save the Earth from total catastrophe.

The Doctor and Ace arrive at a secret military base during World War II, where an ancient evil from the Doctor's past prepares to make his final deadly move. As hideous vampires rise from the sea and Russian commandoes begin to close in, they are confronted not only with a mystery from the distant past but also a terrifying vision of mankind's future...

Ace returns to Perivale to visit her friends, only to find they have been abducted to an alien planet by a race called the Cheetah People who were shown the way to Earth by the Master. The Doctor must find a way off the planet before they all succumb to its savage influence.

The Doctor takes Ace on an initiative test to a strange Victorian old house where she is forced to confront her darkest fears.