1/4 The TARDIS takes the Doctor and Leela to a huge sandminer on an alien world.
The insane computer Xoanon refuses the Doctor's help and prepares to destroy the planet.
The Doctor discovers the terrible truth about Xoanon and realises that he is to blame.
The Sevateem prepare to launch an attack to free their god, Xoanon.
The Doctor arrives on an alien world and is accused of being 'the evil one'.