As the Doctor expects, the electronic “root” is deadly to touch. Elsewhere in the caverns, Sarah is cornered by an Exxilon…one who actually speaks English. His name is Bellal, and he means no harm; he’s a member of a small group of Exxilons who have chosen rationality over the religion based on worship of the city. Before any further introductions can be made, Sarah and Bellal have to hide from two Daleks, who then follow the Doctor further into the tunnels, where they too encounter the “root”…only to discover it’s dangerous to Daleks as well. The root is part of the city’s automated systems, and Bellal reveals that the city is the invention of the Exxilons themselves…and unless they destroy that invention, it will wipe them out. On the surface, the Daleks have subjugated the more primitive Exxilons, turning them into a slave labor force…with help from Galloway, to his crewmates’ disgust. The Doctor and Bellal go to the city to try to gain entry, finding that each successive entryway is locked, and can only be opened by solving logic puzzles…and failing any of these tests could be deadly.
written by Terry Nation
directed by Michael Bryant
music by Carey Blyton and played by the London Saxophone Quartet
Cast: Jon Pertwee (The Doctor), Elisabeth Sladen (Sarah Jane Smith), Duncan Lamont (Dan Galloway), Julian Fox (Peter Hamilton), Joy Harrison (Jill Tarrant), Arnold Yarrow (Bellal), Roy Heymann (Gotal), Michael Wisher (Dalek voices), John Scott Martin (Dalek), Murphy Grumbar (Dalek), Cy Town (Dalek)
Notes: The Doctor claims he’s seen the symbols from the Exxilon city in a Peruvian temple, which means that before the fall of their civilization, they were themselves capable of interstellar travel.
LogBook entry & review by Earl Green