The Mysterious Planet was the unbroadcast title given to the first four episodes of The Trial of a Time Lord, the season-long story that constituted season 23 of Doctor Who. It was written by Robert Holmes, directed by Nicholas Mallett and featured Colin Baker as the Sixth Doctor and Nicola Bryant as Peri Brown.
The story marked the first appearance of the Inquisitor and the Valeyard, two characters who would appear throughout the season, along with Sabalom Glitz, who would appear again later in the season and also in Season 24. With this chapter, the series returned to half-hour episodes. Also beginning with this story, the series was now completely produced on videotape (with the exception, in this story, of a brief special effects sequence in Episode 1).
With this episode, Peter Howell's rendition of the Doctor Who theme was exchanged for a mysterious and surreal arrangement of the theme tune composed by Dominic Glynn. It would remain in use solely for season 23 and close out Colin Baker's era on the series.
This story also introduced some costume changes for the Doctor & Peri. The Sixth Doctor entered his second (and last) full season with a red check vest & cravat and a bright pink watch chain. To help viewers discern between scenes taking place in different points in the Doctor's timeline, scenes set in his past feature him donning his original turquoise cravat & neon green watch chain for the last time; the following story would feature the Doctor's full new outfit in both past and present scenes, and the one after that featured a completely different vest & cravat for the archival scenes, which are set in the Doctor's future.
Notably, Nicola Bryant's character Peri Brown starts wearing more conservative clothing from here out, after spending most of her appearances in loose-fitting and often revealing outfits. Her wardrobe change was a result of complaints that her provocative clothes were inappropriate for younger Doctor Who viewers.
The Doctor is summoned before the High Council of Time Lords to stand trial for the charges of harmful interference to the course of events during his space-time excursions, which have threatened the sanctity of the universe. Indignant at these accusations, the Doctor pleads his case to the Inquisitor with the hope that she will see him as a source of hope and goodwill for existence. However, his prosecuting attorney, a sinister Time Lord known simply as the Valeyard, begins a crusade against the Doctor's life with the motive of painting him out to be a villainous renegade.
The Valeyard's first movement against the Doctor is to review his past interactions on a familiar planet called Ravolox, where he and his-then companion Peri met the morally grey Sabalom Glitz and a tyrannical robot stalking the world's desolated landscape. However, Ravolox holds a terrible truth in the far reaches of its ruins, while the Doctor's trial has its own fair share of startling twists and turns...
The TARDIS materialises in a corridor, and the Sixth Doctor emerges, bewildered and alone. He walks into a room, where he is put on trial for conduct unbecoming a Time Lord. The Inquisitor notes that the Doctor has been on trial previously. The Valeyard states he will argue that the Doctor was shown too much leniency on that occasion. The Valeyard opens the case by using the Matrix to show the Doctor's actions on the planet Ravolox.
The Doctor and Peri arrive on Ravolox, which is virtually identical to Earth. He tells Peri that the official records state that the planet was devastated by a fireball, but the forest they are walking through suggests otherwise. They are seen by Sabalom Glitz and Dibber, who attempt to shoot the Doctor. He moves off just in time. Glitz and Dibber discuss their plan to destroy the "L3 robot" by sabotaging its light conversion system, which has been turned into a totem by a primitive tribe.
The Doctor and Peri explore a cavern. Peri discovers a sign saying "Marble Arch" — a London Underground sign. This means that they are on Earth. Peri begins to mourn for her planet.
The Doctor interrupts the replay to ask what the relevance of this is. He then also asks why Peri is not with him on the station. The Valeyard answers that she is where the Doctor left her, and states that the Doctor's evident temporary amnesia — a side-effect of being taken out of time — should soon pass.
As the Matrix resumes showing the events on Ravalox, Peri is still upset. The Doctor goes into the complex alone. Two masked figures appear and capture Peri. Meanwhile, Glitz and Dibber are brought before Katryca, Queen of the Tribe of the Free. Glitz claims that the totem attracted the fireball that devastated Ravolox, and asks for it to be taken down. The Queen tells him that others have asked for the totem to be dismantled, and none have succeeded. Glitz and Dibber draw their guns, but are overpowered and locked up.
The Doctor finds an underground complex and picks up a bottle of water. This sets off an alarm, and people enter and subdue him. He is accused of stealing water, and sentenced to be stoned. The Doctor tries to block the rocks with his umbrella, but is knocked unconscious.
The Valeyard proposes that the inquiry into the Doctor's activities should become a full blown trial, with the penalty being the termination of his life...
Other officials arrive and break up the stoning. The Doctor is still breathing. Before he can be killed, Merdeen receives a message from the Immortal stating that he wishes to question the Doctor. The Immortal, revealed to be a huge humanoid robot, commands its two assistants to release the service robot.
Peri is brought before Katryca, who informs her that as there are few women, she will need to take many husbands as a member of her tribe. She is put in the same prison as Glitz and Dibber. They tell Peri their plan to destroy the robot. They are taken back to Katryca, who tells them that Glitz will be sacrificed because of his attempt to destroy the great totem.
The Doctor is taken to the Immortal, who introduces itself as Drathro. It commands the Doctor to work with the two assistants. The Doctor identifies the problem, and tries to leave in order to fix it, but Drathro does not allow him to, as his instructions are to maintain an underground system. The Doctor electrifies the robot and his assistants and escapes. Drathro sends the service robot to track down the Doctor. Meanwhile, Peri, Glitz and Dibber overpower the guards and escape. Dibber remains behind to plant a bomb on the black light converter, whilst they go to the underground complex.
In the Marb Station, Merdeen tells Balazar that there has been no fire for hundreds of years, and he should leave the complex. They encounter the Doctor, and Merdeen implores him to help Balazar escape. Peri, Glitz and Dibber, pursued by tribesmen, find the Doctor, and they flee into the Marb Station, but are trapped between the tribe and the service robot. When Peri asks what they should do, the Doctor replies, "I don't know. I really think this could be the end. . . "
The Doctor and Peri are saved when the tribesmen shoot at the service robot and disable it. The Doctor tries to re-enter the underground complex, but the tribesmen insist they all return to the village. There, the Doctor is brought before Katryca. She is unimpressed with his explanation of the true nature of the totem and puts them all back in the prison cell. Glitz confirms that the planet is actually Earth. Drathro reactivates the service robot and sends it to the village. It breaks into the building with the Doctor, stuns him after an attempted handshake and takes him away. The tribesmen disable the service robot and decide to attack the Immortal's castle to steal his technology, believing that they have killed him. Peri rescues the Doctor from the service robot. They set off to the underground complex to stop Katryca and disable the black light system.
The Doctor and Peri encounter Merdeen, one of Drathro's train guards, in the corridors of the underground complex. He tells them that he is hunting. When the Doctor asks who his quarry is, he looks at the Doctor and says, "You". He raises a crossbow weapon at the Doctor and fires...
Katryca and the tribesmen arrive at the castle, where they are confronted by Drathro. He electrocutes Katryca and dismisses the rest of the tribe. The Doctor enters Drathro's domain, promising to help repair the black light system. However, he determines it to be beyond repair, and tells Drathro that he must shut down the black light system to prevent a massive explosion. Drathro refuses as it would mean its own destruction. The Doctor pleads with him, saying that the explosion could destroy the entire universe. That makes Drathro determined to allow what he thinks is a unique event.
Balazar and Peri plead with Merdeen to help them, noting that he would die if the converter exploded. Glitz and Dibber arrive and follow them into the castle through a food chute. Drathro tries to kill them by turning on the food processing system, but Dibber shoots him through the wall. Glitz tells Drathro that they have black light on their ship, and offers to take the robot to the Andromeda Galaxy. Drathro agrees, and leaves with Glitz and Dibber.
The Doctor realises that the black light system has already begun to self-destruct. All he can do is prevent it starting a chain reaction. The system explodes, but the blast only destroys the castle, and as a result Drathro collapses. The Doctor and Peri leave Merdeen and Balazar to take the remaining inhabitants to a new life on the surface.
The Doctor announces to the court that he has saved the Universe, and starts to present his defence. The Valeyard warns the Doctor that he has more evidence to come, and that the court will demand the Doctor's life at the end.
- The Doctor - Colin Baker
- Peri - Nicola Bryant
- The Valeyard - Michael Jayston
- The Inquisitor - Lynda Bellingham
- Katryca - Joan Sims
- Glitz - Tony Selby
- Dibber - Glen Murphy
- Merdeen - Tom Chadbon
- Drathro - Roger Brierley
- Broken Tooth - David Rodigan
- Balazar - Adam Blackwood
- Grell - Timothy Walker
- Humker - Billy McColl
- Tandrell - Sion Tudor Owen
- Drathro Operator - Paul McGuinness
- L1 Robot Operator - Mike Ellis
- Time Lords - Derek Hunt, Leslie Weeks, David Bache
- Underground Guards - Rodney Cardiff, Peter Gates Fleming
- Worker - Laurie Goode
- Natives - Peter Dukes, Christopher Holmes (all DWM 289)
- Assistant Floor Manager - Stephen Jeffrey-Poulter, Sally Newman
- Costumes - Ken Trew
- Designer - John Anderson
- Incidental Music - Dominic Glynn
- Make-Up - Denise Baron
- Producer - John Nathan-Turner
- Production Assistant - Joy Sinclair
- Production Associate - Angela Smith
- Script Editor - Eric Saward
- Special Sounds - Dick Mills
- Studio Lighting - Mike Jefferies
- Studio Sound - Brian Clark
- Theme Arrangement - Dominic Glynn
- Title Music - Ron Grainer
- Visual Effects - Mike Kelt
Cultural references from real world
- Glitz asks the Doctor if he, as a Time Lord, has a ring or a magic lamp to rub.
- When the Doctor is forbidden to look upon the Immortal, he jokes about the risk of being turned into a pillar of salt.
- A hint of identity between Ravolox and Earth is the presence of the Marble Arch station in the underground.
- Sabalom Glitz knows some Latin and lots of Polari, has been to prison many times, has seen many psychiatrists and comes from a polygamous society. He knows of the Time Lords, and is wanted in six galaxies. He's from Salostopus, in the constellation of Andromeda.
- Drathro is also from Andromeda, and he knows of Gallifrey.
- Earth and its "constellation" have been moved "a couple of light years". The Valeyard refers to the galaxy of Ravolox as the Stellian Galaxy.
- The Doctor dates the events on Ravolox as at least two million years after the 20th century.
- Only part of Earth was affected by the solar fireball.
- The sleepers, from Andromeda, found a way into the Matrix 500 years ago and fled to Earth, which was then devastated by a fireball.
- The three sacred books of Marb Station are Moby-Dick by Herman Melville, The Water Babies by Charles Kingsley, and UK Habitats of the Canadian Goose by H.M. Stationery Office.
- The underground dwellers call their world UK Habitat.
- Black light is not the Doctor's field.
- The Doctor has been deposed as Lord President of Gallifrey for neglecting his duties.
- The Doctor doesn't believe in ghosts.
- The Doctor seems about to state his name casually to Peri, but is interrupted.
- The Doctor is called "Old One" by Balazar.
- The Doctor seems to suffer amnesia because of having been taken out of time.
The Doctor's items
- In his pockets, the Doctor carries a torch, an oil can, a paper mask, a teddy bear, and a bag of sweets.
- As Tandrell and Humker rummage through the Doctor's coat pockets, they discover a bag of jelly babies, which the Doctor quickly snatches back before offering each one of the sweets.
Law and order
- According to Glitz, silictone (a material the light converter is made of) is the most expensive metal in the galaxy.
- The black light converter is a Magnum Mark VII.
- The Doctor is under process because of the infringement of the First Law.
- The trial takes place on a Time Lord space station.
- The Valeyard thinks that the High Council were "too lenient", with regards to the Doctor's previous trial and reduction in sentence.
- The evidence is shown from images taken from the Matrix, the repository of all knowledge.
- Despite the change to the 'Doctor Who Theme' arrangement, the title sequence introduced in The Twin Dilemma remained unchanged for the season.
- Beginning with this chapter of The Trial of a Time Lord, Doctor Who returned to its original 25-minute episode format, which it retained for the remainder of the original series. However, the total length of the broadcast season remained fixed at about three months annually, resulting in about a 50% drop in seasonal output as compared with previous seasons.
- While listed as a single story, this story and the three others that make up The Trial of a Time Lord are in fact one long story with fourteen parts. This makes it the longest Doctor Who story ever, with the second being The Daleks' Master Plan, which has twelve parts.
- In an interview in Doctor Who Magazine 448, Timelash author Glen McCoy said that he came up with the idea of the Doctor being put on trial.
- Beginning with this story, all exteriors would be recorded using Outside Broadcast video, rather than film as had usually been the practice for the previous 22 years. The use of OB for exteriors would continue for the remainder of the original series, until its end in 1989.
- The filmed insert that begins part one of a special effects sequence involving the TARDIS and the space station would be the last shot-on-film footage made for Doctor Who until the 1996 TV movie. Ironically, the Fox network recycled this footage for its promotional advertisements for the film (even though it wasn't included in the movie). The series revival from 2005 to the present uses videotape which is later processed to look like film, though small parts have been shot on film.
- The model of the space station was six feet wide. The 45-second-long opening scene of it from this story was the first use of a motion-control camera on Doctor Who, took a week to film, and cost over £8,000 making it the most expensive Doctor Who sequence to date. John Nathan-Turner justified the sequence's cost as it was the first new scene shown to viewers after the programme's hiatus, and by reusing parts of it as establishing shots for the rest of the Trial stories. 
- The Radio Times programme listing for part one was accompanied by a black and white publicity still of the Inquisitor and the Doctor in the courtroom, with the accompanying caption "Can the Doctor (Colin Baker) convince the Inquisitor (Lynda Bellingham) that he hasn't been misusing his time? / BBC1, 5.45 p.m. Doctor Who".
- In a featurette included with the 2008 DVD release, Nicola Bryant states that "some time has passed" since the events of Revelation of the Daleks, and therefore she and Baker played their roles as if the two had grown closer over time. Exactly how much time passed for the characters during the show's 18-month hiatus has never been established. The Doctor in this story states he is 900 years old, the same age given in Revelation; however in an episode of The Ultimate Foe, Mel states the Doctor's age as "900-odd" suggesting this is an approximation (or it reflects the fact the Doctor meets Mel at a later time than he does Peri).
- Sabalom Glitz returns in the final segment of the trial and later in Dragonfire. Since he is shown collaborating with the Doctor in the later stories, he is sometimes referred to as a companion, though there is no indication that he was ever officially considered such by the BBC.
- Part one - 4.9 million
- Part two - 4.9 million
- Part three - 3.9 million
- Part four - 3.7 million
- The unnamed character, "the Inquisitor", is Flavia, last seen in The Five Doctors and presumably regenerated. This question remains unanswered in terms of televised episodes. Spin-off works, however, give her a different name, Darkel.
- While shooting publicity photographs for the Trial season, and also when doing television interviews promoting the season, Colin Baker sported a beard; this led to the mistaken assumption by media and fans that the Doctor would be bearded during this and the other stories.
- Rumours indicated that the Doctor's name would be revealed. The Doctor seems about to state his name rather casually to Peri while musing about a paper he wanted to write, but he is interrupted just before he says his name, or an alias he wished to use for the book.
- Queen Elizabeth Country Park, Gravel Hill, Horndean, Hampshire
- Butser Ancient Farm Project (now known as Little Butser), Butser Hill, Hampshire
- BBC Television Centre (TC6 & TC3), Shepherd's Bush, London
- Grell is still visibly breathing after his death in part four.
- The Doctor's pants change design frequently, between striped yellow and brown to fluorescent yellow, without explanation.
- Though the Doctor was again elected to the Presidency of the High Council of Time Lords in The Five Doctors, he has been deposed by the time of this story for leaving the office vacant too long. This doesn't stop the Seventh Doctor from later using the title in Remembrance of the Daleks.
- The trial depicted in Episode 10 of The War Games is referenced here by the Inquisitor as the Doctor having "been on trial already for offences of this nature". In response, the Valeyard contends that the High Council were "too lenient" with the sentence that resulted from that trial. Although not referenced directly, the sentence in question was the forced regeneration of the Second Doctor and his subsequent exile to Earth, the latter of which was lifted in The Three Doctors.
- Sabalom Glitz returns in the final segment of the trial and later in Dragonfire.
- At one point, Sabalom Glitz and Dibber come to a locked door. Glitz assesses that the only way through the door is to blast through. He says, "Five rounds, rapid ought to do the trick" — an almost certain reference to one of the Brigadier's most famous lines from TV: The Dæmons.
- The Earth was also briefly moved from its location in the 21st century. (TV: The Stolen Earth). In The Ultimate Foe, it is revealed that the Earth was moved by the Time Lords using a magnetron. In TV: Journey's End, it is revealed that the Daleks moved the planet with their version of the device, although the episode also established that a single TARDIS, operating at full power and with a full complement of crew, is capable of moving the planet (albeit with a little help from the Cardiff rift). Gallifrey eventually is relocated briefly to Earth's solar system in TV: The End of Time.
- In AUDIO: The Dark Flame it is explained what exactly "black light" is. It is not ordinary ultraviolet light, but energy from quantum meta-fluctuations in the space/time continuum.
- When recovering from the service robot's attack, the Doctor briefly refers to Peri as "Sarah Jane," and speaks in the mannerisms of his third incarnation.
- The Doctor says he is 900 years old, as in TV: Revelation of the Daleks.
Home video and audio releases
- This story was released as Doctor Who: The Mysterious Planet
- It was released:
- UK October 1993 (released with the other The Trial of a Time Lord stories in a TARDIS-shaped tin with a random picture of one of the (then) seven Doctors on the base)
- US October 1993 (same as the UK release except packed in a cardboard box in honour of Doctor Who's 30th anniversary)
- Australia October 1993
- Audio Commentary 1 featuring Colin Baker, Nicola Bryant and Tony Selby
- Audio Commentary 2 (Part 1 only) featuring Eric Saward
- The Making of The Mysterious Planet
- Deleted and Extended Scenes
- Trails and Continuity
- 35mm Film Sequence featuring opening model shot from Part 1
- Music Videos featuring the new theme music and trial theme
- Production Subtitles
- Wogan interview with Colin Baker and Lynda Bellingham
- Blue Peter segment featuring Janet Ellis and Mike Ellis showing the L1 and Drathro special effects
- Photo Gallery
- The Mysterious Planet at the BBC's official site
- The Mysterious Planet at BroaDWcast
- The Mysterious Planet at Shannon Sullivan's A Brief History of Time (Travel)
- The Mysterious Planet at The Locations Guide
- The Tardis Library: Video release information for The Mysterious Planet