The Doctor answers a summons and finally returns to his homeworld, Gallifrey, seat of the Time Lords. However, when the President of the High Council is assassinated, he becomes the prime suspect, while an old enemy lurks in the shadows, pulling the strings.
The TARDIS materialises in a hostile jungle on the planet Spiridon. Jo sets out alone to find help for the Doctor, who has fallen into a coma. She meets a party of Thals and is left in hiding aboard their crashed spaceship while they go to the Doctor's aid. The Time Lord, now recovered, learns of their mission to destroy a party of Daleks sent here to discover the native Spirid...
