An unnamed planet, the distant future. Arriving in a place that seems oddly familiar, the Doctor finds the savage Sevateem tribe battling to free their captive god, Xoanon, from the Evil One and his Tesh servants. But can the whole situation really be the Doctor's fault?

The Sevateem launch another attack to try to free Xoanon as the Doctor tries to figure out his role in their past. But his only chance to win their trust is to face a deadly test.

The Doctor has broken through the barrier and found the Tesh. But he comes to an awful realisation about Xoanon.

The Doctor tries to fix the mad computer Xoanon. But it is determined to stop him – even if it must destroy the entire world!

An unnamed world, an unknown time. A vast mining vessel trawls a sea of mineral sand for valuable ores, the tiny human crew served by an army of humanoid robots. But as the Doctor and Leela arrive, one of the crew is found murdered... and if they didn't do it, who did?

The Doctor and Leela are suspected of murder. But the real foe is using robots to cut down the crew – and even sabotage the sand miner itself!

One of the crew is the insane Taren Capel, who is using robots to carry out the murders. The Doctor discovers that there are also others who aren't what they appear to be either.

The Doctor and the surviving humans fight for their lives against Taren Capel and his growing army of deadly robots.

England, the late 1970s. At Fetch Priory, Dr Fendelman's experiments with the new Time Scanner are disrupted by the mysterious death of a hiker, nearby. Then there's the mysterious skull, also being used as part of his work. A skull that seems to predate the evolution of mankind. What is the true role of the Fendahl in humanity's evolution?

The mystery surrounding the strange skull deepens. Thea is slowly succumbing to its influence while the Doctor prepares to battle a creature from mythology.

While Max prepares to tap supernatural forces beyond imagining, the Doctor and Leela investigate the legend of the Fendahl.

The Fendahl is returning to life, ready to consume everything in its path. Can the Doctor find a way to kill death itself?