After discussing their pupil Susan, two teachers follow her to a junkyard. They meet her grandfather, the Doctor, and force their way inside a police box. Show more

The Cave of Skulls: The TARDIS travels back to Stone Age times, where the crew make the mistake of venturing outside. Show more

The Forest of Fear: The Doctor and crew leave the TARDIS to explore their new surroundings, but are captured, thrown in a cave and threatened with death. Show more

The Firemaker: The Doctor decides that the only way to escape is to show the Stone Age cave dwellers how to make fire. Show more

The travellers explore the surface of a new world. Everything is dead, but beyond a petrified jungle they see a metal city which the Doctor is determined to explore. Show more

Looking for Barbara, the Doctor, Ian and Susan learn that they have been exposed to lethal doses of radiation. The travellers are confronted by the city's inhabitants - the Daleks! Show more

Fearful of a Thal attack, the Daleks force Susan to trick the Thals. Realising that the Daleks are planning an ambush, the four travellers try to escape and warn the Thals.

Pretending to be a Dalek, Ian finds that that he is trapped inside the casing. The Doctor, Susan and Barbara have no choice but to abandon Ian as the real Daleks arrive and attack.

Ian and Barbara join a Thal expedition that will penetrate the Dalek city from the unguarded mountains behind it. Their journey is a dangerous one, and not all will survive.

The Doctor and Susan are once again taken prisoner by the Daleks. In the mountains, Ian, Barbara and the Thals must negotiate a vast chasm to reach the city.

The Thals and the time travellers attack the Daleks from all sides as the Daleks start the countdown to release deadly doses of radiation into the atmosphere.

The TARDIS lands in Tibet in 1935. There the Doctor is accused of murder by Professor Travers who is in search of the legendary Yeti. Show more

Jamie and Victoria make an incredible discovery in a cave on the mountain. The Doctor is tied to the gates of the Detsen Monastery as a lure for the hostile Yeti.

As the Great Intelligence manifests itself on Earth, the Doctor makes a last, desperate attempt to repel the evil entity by pitting his mind against it in a mental battle. Show more

When a Yeti is captured by the Detsen monks, the Doctor discovers that it is a robot – but its control sphere is missing. Elsewhere in the monastery, the sphere is on the move. Show more

Imprisoned in the monastery, Victoria is able to escape. The old High Lama is in the control of the alien Great Intelligence which plans to invade Earth. Show more

Discovering that his old friend, Padmasambhava, is still alive after three hundred years, the Doctor goes to confront him. The Great Intelligence prepares to make its final move. Show more

The TARDIS returns to present day Earth, where Sarah is caught in a rock fall and becomes possessed by the fossilized stone hand of the alien Eldrad.

At the nuclear power station, the stone hand has come to life and is determined to gain access to the reactor core.

The hand has used the nuclear energy to regenerate itself into the female form of the alien Eldrad, who demands that the Doctor return her to the planet Kastria.