Parts: 4
Writer: Andrew Smith
Airdates: 25 October 1980 - 15 November 1980
Production Code: 5R

Doctor: fourth
Companions: the second Romana, Adric, K-9 mark two

Creature Feature: Marshmen

Story: The Time Lords have summoned Romana back to Gallifrey, but en route, K-9 loses control of the TARDIS. When it lands, the screen shows an image of Gallifrey, but the planet outside is far too lush to be the Doctor's home world. Romana is somewhat relieved, as she did not want to return, but the Doctor is determined to find out what has gone wrong.

On the planet, Alzarius, strange things are startening to happen - signs that, fifty years ago, heralded an unusual event. Spider eggs are found inside local riverfruit, the waters begin to boil, and mist shrouds the land. The villagers, frightened of Mistfall, lock themselves away in their crashed starliner to wait it out. Meanwhile, Adric, one of the local youths, tries to prove his worthiness to the local youth gang by stealing one of the riverfruits. He is pursued by a Decider, who falls and hits his head. In front of a horrified Adric, the man is dragged into the water by an unseen hand.

What secrets are the Deciders hiding from their people? What is the connection between the spiders, the Marshmen and the Alzarians? And can they escape the planet, or will Mistfall claim them all?