After causing a volcanic eruption at the end of The Dominators, the Doctor, played by Patrick
Troughton with Jamie (Frazer Hines & Hamish Wilson) and Zoe (Wendy Padbury) must escape quickly, so the Doctor has to use the emergency unit to take the TARDIS away from danger and indeed out of reality itself...
The story is quite unlike any other Doctor Who story. It is one of the most surreal stories, along with The Celestial Toymaker and Warrior's Gate. However The Mind Robber works well due to the fact that the Doctor and his companions realise exactly where they are, and are able to solve the puzzles to escape The Land of Fiction.
As you may be aware of, during filming Frazer Hines became ill with chicken pox. Fortunately, due to the surreal nature of this story they were able to come up with a witty way to replace him temporarily with Hamish Wilson in episode two.
Apparently, Peter Ling who wrote this story came up with the idea whist taking a train journey with story editor Derrick Sherwin and his assistant, Terrance Dicks. Peter Ling commented how fans of soap opera's think that the characters are real. He was a writer on the original Crossroads series. His colleagues told him to write the story for Doctor Who. He originally called it The Fact Of Fiction.