England, the near future. A strange anti-matter creature arrives on Earth and attacks UNIT HQ. It seems to be specifically seeking the Doctor out - but why? With the Time Lords themselves unable to help, it seems the only person who can help the Doctor is himself - or selves...

The third Doctor and Jo find themselves on an artificial world inside the black hole while the second Doctor tries to find a way to control the organism.

The Time Lord Omega reveals himself to the third Doctor along with plans for vengeance against his own kind.

Omega reveals the purpose behind bringing the Doctor to his antimatter world, but the Doctor(s) discover a startling fact about Omega that he didn't know himself and eventually strike a bargain.

The Doctor attempts to test his new dematerialisation circuit by taking Jo to Metebelis Three but instead the TARDIS arrives in the hold of a 1920s cargo ship.

The Doctor and Jo return to the Bernice to try and aid their escape but find themselves pursued by the Drashigs.

The Doctor escapes from the Scope and joins forces with Vorg to try and save its inhabitants but Kalik is still determined to use the Drashigs to start a rebellion.

The Doctor and Jo land on a spaceship in the far future as it is attacked by Ogrons, which the human crew see as Draconians. The Doctor and Jo are taken to Earth as spies.

The Doctor and Jo are taken to Earth, where both humans and Draconians believe them to be a spy for the other side.

The Doctor is sentenced to life imprisonment at a lunar penal colony while Jo encounters an old enemy.

The Master rescues the Doctor from the lunar penal colony, aiming to take him and Jo to the Ogrons' planet, and the Doctor's attempt to escape leaves him stranded in space.

The Doctor, Jo and the Master are taken to Draconia, where the Doctor tries to convince the Draconians of the truth.

The Doctor, Williams and the Draconian Prince head to the Ogrons' planet to find evidence of the Master's actions but the Master tricks Jo into leading them into a trap.

The planet Spiridon, the year 2540. The Doctor and Jo arrive on the trail of the Daleks, and find unexpected allies in the shape of a Thal suicide squad. But what has brought the Daleks here in the first place?

The Doctor is captured by the Daleks, while Jo is rescued by a friendly Spridon named Wester.

The Doctor and Codal escape from their cell and meet up with the Thal commandos who are trying to get into the Dalek base.

The Doctor and his friends escape from the Dalek base, prompting the Daleks to devise a plan to wipe them out.

The Doctor and his friends ambush two Daleks as part of their plan to get back into the city, but the Daleks are on the verge of unleashing their virus.

The Doctor and his friends prepare to refreeze the Dalek army but the Dalek Supreme has arrived on the planet determined to destroy them all.

While the Doctor plans a holiday to Metebelis Three, Jo and the Brigadier are intrigued by a mysterious death at a coal mine in Llanfairfach, which is being blamed on local company Global Chemicals.

The Doctor and the Brigadier attempt to rescue Jo and Bert from the mine but Global Chemicals prove distinctly uncooperative.

The Doctor and Jo manage to escape from the mine with a maggot egg but Stevens is determined to stop them analysing it.

The Brigadier calls in a full UNIT force to deal with the giant maggots while the Doctor infiltrates Global Chemicals to find out what is really going on.

The Doctor manages to escape from BOSS with help from Yates and discovers Cliff has been infected by a giant maggot.

The Doctor attempts to destroy the giant maggots and cure Cliff but the real threat is BOSS, who is poised to take over all the world's computers.