Stardate 5431.4: The Enterprise is intercepted by a starship of unknown design and a woman from the ship beams directly into the bridge and uses a device to render the Enterprise's crew unconscious. She then walks over to Spock... When the crew awakens, McCoy summons Kirk to sick bay and informs him that the alien visitor apparently removed Spock's entire brain without even performing surgery. After Spock's body is fitted with a device that allows McCoy to control the Vulcan's motor functions with a remote control, Kirk starts a search for Spock's brain, hoping it can be recovered and somehow returned to Spock before his body decays.

Trying to escape from a volcanic eruption, the Doctor activates the TARDIS' emergency circuits, taking his ship out of real time and space altogether. However, the void is inhabited by a hypnotic force which lures Jamie and Zoe outside, keeping the Doctor distracted until the strain on the TARDIS becomes too great and the ship explodes. The Doctor and his companions find themselves in a Land of Fiction, where wordplay can be deadly and fictional characters come to life. The travellers must make their way to the castle at the centre of the Land, while the Master of the Land of Fiction waits for them to make the wrong move and transform themselves into fictional characters and thus pawns under his control.