The newly regenerated Doctor escapes with his companions back to the TARDIS. Suffering from post-regeneration trauma, he only narrowly manages to save the ship from destruction as it plunges back to Event One, the hydrogen in-rush that preceded the creation of the universe. He then seeks sanctuary in the peaceful domain of Castrovalva, only to discover that it is an illusory, dimensionally paradoxical trap set for him by the Master with the unwilling aid of a kidnapped Adric