Astronauts rescued from a mission to mars are kidnapped when they arrive back on earth. They seem to have been irradiated, and can now kill people merely by touching them. But the Doctor discovers the astronauts have been replaced with Alien ambassadors who are being forced to behave in a hostile manner. With The Doctor traveling to the alien mother ship, and Liz kidnapped, The Brigadier is left wondering who to trust.

Elizabeth Cane arrives in Mexico and starts to take an interest in a bull fighter, but he can find only contempt for this refined American woman and what she represents.

A rebellious youth, sentenced to a boy’s reformatory for robbing a bakery, rises through the ranks of the institution by impressing its Governor through his prowess as a long distance runner. He is encouraged to compete in an upcoming race, but faces ridicule from his peers.

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.

The Doctor needs somewhere peaceful to recover from his traumatic regeneration. But the sanctuary of Castrovalva is not all it seems, as the Master will stop at nothing to gain his revenge over the Doctor...

In the year 4000, the Daleks conspire to conquer the Solar System. Their scheme involves treachery at the highest levels and a weapon capable of destroying the very fabric of time. Only the Doctor and his friends can prevent catastrophe — and there is no guarantee they will escape with their lives...

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.

A publisher is nearly framed for murder, but he appears to have been goaded by the blackmailer who has also blackmailed the publisher's wife.