In defeating the Dominators on Dulkis, the Second Doctor sets off a volcanic eruption. He leaves the TARDIS, along with his companions, Jamie and Zoe, in the way, though, and it gets buried in lava, blowing a fluid link in the process. This forces the Doctor to use the emergency unit to take the TARDIS away from danger and indeed out of reality itself.
They land in a white void and as the Doctor fixes the TARDIS, Jamie and Zoe are lured outside and are confronted by white robots. The Doctor gets them back inside but, as they try to return to reality, the TARDIS explodes and the travellers are scattered into nothingness.
They end up in a forest where the trees become letters when seen from above. The Doctor, after facing a series of riddles, finds Jamie, but accidentally changes his face. They are soon reunited with Zoe and then encounter Lemuel Gulliver, who gives them away to life-sized toy soldiers. They are taken to the edge of the forest, where a unicorn charges at them. They manage to turn it into a statue by loudly declaring that ‘it doesn’t exist.’
They continue on and reach a house, where the Doctor brings Jamie back to normal. They discover that the house is the entrance to a labyrinth. Here, while leaving Jamie behind, the Doctor and Zoe encounter the Minotaur and Medusa, whom they deal with in the same way as the unicorn.
Jamie, pursued by a soldier, climbs up a rock face with the help of Rapunzel’s hair and enters a citadel through a window, triggering an alarm. He hides and finds Gulliver, who cannot see the White Robots who are chasing Jamie.
The Doctor and Zoe exit the labyrinth and encounter the Karkus, a cartoon character from Zoe’s home era. The Doctor accidentally manages to dispel the Karkus' "anti-molecular ray disintegrator" by commenting that no such weapon exists, and the Karkus attacks them. Unfortunately the Doctor can't get rid of the Karkus, because he has never heard of the character before and cannot say for certain that the Karkus is not real. Zoe, however, beats the Karkus into submission with her martial arts skills, and he allies himself with them. He takes them to the citadel, where they find Jamie. Zoe accidentally sets off the alarm again, but the trio do not hide and instead let the robots take them to the main control room.
Here, they meet the Master, a kidnapped Earth writer who underwent the same tests as them when he first arrived. He explains that he is getting old and needs the Doctor to replace him as creative source for the Land of Fiction. While he is talking, Jamie and Zoe sneak into a library area where they encounter the White Robots again and become trapped in a giant book, turning them into fictional characters. The Doctor refuses the Master’s offer and climbs out through a skylight. The Master uses Jamie and Zoe to trap the Doctor and links him up to the Master Brain. The two battle, summoning up various fictional characters to fight against one another. The Doctor prevails, releasing Jamie and Zoe who overload the Master Brain, leaving the White Robots with only the final order to destroy.
The Doctor unplugs the Master from the Brain and they all retreat to a side room. The White Robots destroy the Master Brain, the TARDIS comes back together and normality is restored.
The Master is not the same character as the renegade Time Lord known as the Master.
The fluid link that is blown at the start of the serial is also mentioned in the First Doctor serial The Daleks. In that serial, however, the Doctor claims it had run low on mercury, though this later turns out to be a ruse to convince companions Ian Chesterton and Barbara Wright to explore the planet on which they had just landed. Its explosion two serials previously, in The Wheel in Space, forced the Doctor and Jamie to evacuate the TARDIS to escape the toxic fumes and find more mercury.
One of the fictional characters encountered is the minotaur of Greek mythology. Variations on this myth were used again in the Third Doctor serial The Time Monster and the Fourth Doctor serial The Horns of Nimon. A minotaur-like creature (from a species close to the Nimon) appears in the Eleventh Doctor story "The God Complex".
The Land of Fiction also features in the Virgin New Adventures spin-off novels Conundrum and Head Games by Steve Lyons. In Conundrum, it is revealed that the Land of Fiction was created by the Gods of Ragnarok. The novels, like all spin-off media, are of uncertain canonicity. It features once more in the Big Finish Productions audio adventures City of Spires, Night's Black Agents, The Wreck of the Titan, and Legend of the Cybermen, this time featuring the Sixth Doctor (though the protagonists do not realise this until the very end of Titan).
Working titles for this story included Man Power, Another World and The Fact of Fiction. The Mind Robber was originally composed of four episodes, but the preceding serial, The Dominators, was reduced from six to five episodes. This resulted in a sparse first episode being written, as they had to use the limited budget of the replaced episode. This stretching of the story also resulted in the first four episodes only running between 19 and 22 minutes in length, and Episode 5 being the shortest Doctor Who episode ever at slightly over 18 minutes.
During production, actor Frazer Hines contracted chickenpox and was hurriedly replaced by Hamish Wilson for episode 2. This also meant that a scene had to be quickly written to explain Jamie's sudden change in appearance. On both occasions before Jamie gets turned into a cut-out, he shouts, "creag an tuire". Frazer Hines joked on the DVD commentary that this is Scottish Gaelic for "vodka and tonic". It is close to the MacLaren clan's slogan "Creag an tuirc".
Location filming for The Mind Robber took place in June 1968 at Harrison's Rocks in Sussex and Kenley Aerodrome in Croydon. Other filming took place in the same month in Ealing Studios, while studio recording for episodes one and two also took place in June. Studio recording for episodes three, four, and five took place in July 1968. The white robots that close in on Jamie and Zoe in the void outside the TARDIS had been loaned from a previous use in the British science fiction television series Out of the Unknown.
Bernard Horsfall later played a Time Lord in The War Games, Taron in Planet of the Daleks and Chancellor Goth in The Deadly Assassin. He also played Arnold Baynes in the audio play Davros. Christopher Robbie appeared in Revenge of the Cybermen, playing the Cyberleader. Ian Hines, who plays one of the soldiers, is the brother of Frazer Hines.
Jack Harkaway was the name of a character from a Penny Dreadful called Boys of England. Harkaway was first introduced in 1871.
Although a caption at the end of Episode 5 advertised The Invasion for the next week, it would be three weeks before it was broadcast due to the BBC's coverage of the 1968 Summer Olympics. The story was repeated on BBC2 on consecutive Fridays from 31 January – 28 February 1992, achieving viewing figures of 2.57, 2.64, 1.5, 1.5 and 3.46 million respectively.
The BBC's Audience Research Report showed a mostly negative reaction from viewers, with "just under a third" reacting favourably. The complaints mainly were around the story being more fantasy-oriented rather than the more dignified science fiction, making it seem "silly". Others liked the concept, but felt it was too complicated for children.
Paul Cornell, Martin Day, and Keith Topping wrote of the serial in The Discontinuity Guide (1995), "The combination of disturbing images (Jamie having his face taken away), superb literalism ('When is a door not a door?') and set pieces (the mental battle for control of Jamie and Zoe) makes this is one of the most memorable stories of the era." In The Television Companion (1998), David J. Howe and Stephen James Walker praised the story's inventiveness, stating that it "remains a hugely enjoyable story, and one that stands up to repeated viewing". However, they said that the various characters that did not contribute much made the story "a bit of a jumble", and the fact that the serial was elongated by an episode had added padding. Howe and Walker also felt that the story went "downhill" after the "wonderful" first episode. In 2009, Mark Braxton of Radio Times praised the story's "brave" premise and its "delightful" but subtle humour. He also wrote that the inhabitants of the Land of Fiction were "well cast", despite being "middle-class" and "bookish". The A.V. Club reviewer Christopher Bahn described it as "one of the series' most genre-breaking and forward-thinking stories", with the various elements "creepy and frightening" rather than played for camp. While he noted the confusion of where reality ended and the Land of Fiction began and the ambiguous ending that did not seem to affirm if they had escaped it or not, Bahn felt that it had a "weird effect" of strengthening the theme of the danger being the Doctor's ongoing story. In 2010, Charlie Jane Anders of io9 listed the cliffhanger to the first episode — in which the TARDIS breaks apart — as one of the greatest cliffhangers in the history of Doctor Who.
A novelisation of this serial, written by Peter Ling, was published by Target Books in November 1986.
The Mind Robber was released on VHS in May 1990, and released on Region 2 DVD on 7 March 2005, and in North America on 6 September 2005.