The TARDIS arrives in the Himalayas. But before The Doctor and his two companions, Jamie McCrimmon and Victoria Waterfield, go outside to explore their new surroundings The Doctor rummages through a chest looking for a bell. On its discovery he tells his companions that this 'ghanta' will ensure them the welcome of a lifetime.
Outside The Doctor is delighted to see the fortified walls of a monastery nearby. He also spots, on the ground, a large set of footprints. Concerned by this he decides that Jamie and Victoria are to stay in the TARDIS while he goes to the monastery alone. However, after he has gone, Jamie and Victoria decide to explore anyway. Outside they also find the footprints and decide to follow them up the mountain.
On his way down to the monastery The Doctor comes across the remains of a campsite, a lifeless body and a rucksack which he picks up. He soon arrives at the monastery which at first appears deserted. But soon after arriving the gates open and he is met by the resident monks and an explorer called Professor Travers who, on seeing the rucksack, accuses The Doctor of attacking him and murdering his companion. The Doctor protests his innocence but one of the monastery's monks, Khrisong, orders that The Doctor be taken away and locked up.
|Victoria and Jamie on the Mountains
Meanwhile further up the mountain Jamie and Victoria find that the footprints lead to a small cave. While Jamie goes inside to investigate, Victoria stays outside. But when she sees a large hairy creature lumbering towards her she enters the cave so as to warn Jamie. She finds that Jamie has discovered something very odd at the back of the cave – a small pyramid made up of silver spheres. On informing Jamie about the creature outside they retrace their steps back to the cave entrance but to their horror instead of passing by the creature, on reaching the mouth of the cave, starts to enter it. Just as it is about to discover them Jamie accidentally knocks away one of the props that supports the roof and rubble crashes down on top of the creature enabling Jamie and Victoria to escape from the cave and run down the mountain, chased by the recovered creature.
Back in the monastery The Doctor confides in a young monk called Thonmi whom he tells about the ghanta that he has hidden in his cell. It is then that The Doctor is brought before Khrisong. But instead of being allowed to go free The Doctor is tied to the doors of the monastery while up on the mountainside three Yeti look down. Khrisong explains that the Yeti will decide if he is guilty or not; if he is guilty the Yeti will rescue him; if he is innocent they will attack him.
|The Doctor and Thonmi
Rescue though is at hand from two places. Firstly Thonmi, who had discovered the ghanta in The Doctor’s cell, takes it to Songsten who confirms that it is the same holy bell that was entrusted to a stranger long ago and had thought to be lost to them. Songsten, on hearing the voice of Padmasambhava telling him that The Doctor is known to him and must not be harmed, instructs Thonmi to have The Doctor released.
Just as the Yeti approach The Doctor, his two companions arrive at the monastery. On the way down from the cave they had meet Travers and learnt about The Doctor’s plight. Travers though is more interested about the creature and Jamie’s discovery in the cave. In return for promising to show him the cave, Travers agrees to return to the monastery, with Jamie and Victoria, so as to clear The Doctor’s name.
With The Doctor released, and with the help of Jamie, they are able to capture one of the creatures. It is then that The Doctor discovers that it is in fact a robot which is now lifeless. The Doctor also discovers a spherical hole in the robot's chest. What they don’t at first realise is that a silver sphere, like the ones Jamie discovered in the cave, was knocked from the Yeti during its capture. Unnoticed it is inside the monastery and seems to be alive as it rolls along the floor.
|Victoria and Jamie Explore a Cave
The Doctor and his two travelling companions are about to discover that all is not well at the monastery. With disharmony amongst the monastery's monks and the countryside overrun by the Yeti, The Doctor realises that an extra dimensional force called the Great Intelligence is controlling the Yeti so as to scare away or kill anyone who approaches the monastery. The Doctor is also amazed to learn that Padmasambhava, who he met during a previous visit, is still alive and goes to see him. Padmasambhava tells The Doctor how he made contact with the Great Intelligence and how the alien is controlling him to further its plans to take control of the Earth.
When it is revealed that the Yeti are controlled from a secret room beneath the inner sanctum The Doctor is able to distract the Great Intelligence by using his own mental powers, so allowing Jamie and Thonmi to destroy the Great Intelligence's links with Earth. With the Great Intelligence’s hold over Padmasambhava broken the three hundred year-old master is allowed to finally die in peace.
With the Yeti no longer a threat The Doctor and his companions make their way back to the TARDIS. They are accompanied by Professor Travers. But when the explorer sees a genuine Yeti, further up the mountain, he chases after it leaving The Doctor, Jamie and Victoria to depart unnoticed in the TARDIS.