Accused of 'crimes against the inviolate laws of evolution', the Doctor is on trial for his life. The sinister prosecutor, the Valeyard, presents the High Council of Time Lords with the second piece of evidence against the Doctor: a dramatic adventure on the planet Thoros-Beta which led to the renegade Time Lord's summons to the Court of Enquiry. But as the Doctor watches the scenes on the Matrix he is puzzled by what he sees - his behaviour is not as he remembers. Only one thing is certain: on the evidence of the Matrix the Doctor is surely guilty as charged...

The TARDIS has stalled in mid-flight, and it is only on the planet Varos that the Doctor can find the precious Zeiton-7 ore he needs to continue his travels through time and space. Arriving on the planet, he saves the rebel Jondar from execution, and incurs the wrath of Sil, the sadistic representative of the Galatron Mining Corporation on Varos. The hunt is on for the Doctor and his rebel friends. And as they are pursued through the corridors of the deadly Punishment Dome, the Doctor discovers that the people of Varos have some very disturbing ideas of entertainment...

'Did I hear "Doctor"? Is it the Doctor I have drawn to me?' The laugh became more strident, forcing the Doctor to thrust his fingers into his ears in panic and close his eyes, as if here were a frightened child.

The TARDIS has been pulled off course and sent hurtling through space and time. When it finally stops, Peri is amazed to witness the Doctor's transformation into a cringing coward. The takeover of the TARDIS by the school bully from the class of the fourth millennium on Gallifrey is only the first of the Doctor's problems. On the surface of the planet Magnus more of his old enemies are conspiring to trick the planet's all-female rulers; the Doctor and Peri have to foil a plot to freeze the entire world and wipe out most of the population.