The Keys of Marinus is the fifth serial in the British science fiction television series Doctor Who, which was first broadcast on BBC TV/BBC1 in six weekly parts from 11 April to 16 May 1964.
Written by Terry Nation and directed by John Gorrie, the serial takes on a "mini-adventures" format, in which the First Doctor (William Hartnell), his granddaughter Susan Foreman (Carole Ann Ford), and her teachers Ian Chesterton (William Russell), and Barbara Wright (Jacqueline Hill) search for four keys to restore the Conscience of Marinus, a computer which maintains law and order.
The First Doctor (William Hartnell), his granddaughter Susan Foreman (Carole Ann Ford), and her teachers Ian Chesterton (William Russell) and Barbara Wright (Jacqueline Hill) arrive on a small island on the planet Marinus where they meet Arbitan (George Coulouris), Keeper of the Conscience of Marinus—a vast computer developed as a justice machine which kept law and order across the entire planet.
Arbitan explains that the society of Marinus is in danger, as the Voord, humanoid creatures protected by amphibian-like black rubber wet suits, are seeking to enter the tower to take control of the Conscience.
To prevent this, the Conscience requires five keys, and Arbitan coerces the Doctor and his friends to gather them by placing a force field around the TARDIS.
The Keys of Marinus was written to replace a different script, Dr Who and the Hidden Planet by Malcolm Hulke, which was deemed problematic and required rewrites.
[8] Carole Ann Ford was displeased with the portrayal of Susan in the serial, as she felt that she was written like a child,[9] describing her character as "pathetic".
For the role of the Voord, among other villains, three young actors, who were friends of Gorrie, were cast: Martin Cort, Peter Stenson, and Gordon Webster.
For the shots of the wolves in the fourth episode, the BBC purchased 14 feet of film from the 1957 Russian thriller Seryy razboynik (The Grey Robber) from distributor Sovexport.
The drop in viewers for the sixth episode was attributed to the absence of Juke Box Jury—the programme that followed Doctor Who—which was replaced by the film Where Coco Lives.
Bob Leeson of the Daily Worker felt that the fifth episode of the serial was the show's low point, noting that the introduction of a trial scene represented a rushed script.
[1] In The Discontinuity Guide (1995), Paul Cornell, Martin Day, and Keith Topping felt that the episodic narrative left little room for each story to develop, and that the show's limited budget was evident.
[23] In The Television Companion (1998), David J. Howe and Stephen James Walker praised Cusick's work with a limited budget, and enjoyed the serial's conclusion.
[25] In a 2008 review, Patrick Mulkern of Radio Times wrote that "standards slip appreciably" after the four preceding serials in terms of "ambitious but slapdash" script quality, as well as the below-par sets and supporting characters.
[26] In 2009, Graham Kibble-White in Doctor Who Magazine derided Susan's character for "devolving into a bit of a shrill", but was generally positive towards the episodic story structure and the timing of Hartnell's holiday.
[29] Arnold T. Blumberg of IGN described the serial as "a clichéd premise ... handled poorly and with no spark at all apart from Hartnell's late-hour rally".
[31] While remastering the serial for the DVD release, it was discovered that the second and fourth episodes had been slightly edited; off-air soundtracks recorded by David Holman were used to restore the cuts.
[22] Sound effects from the serial, under the title "Sleeping Machine", were included on Doctor Who: The 50th Anniversary Collection, originally released on CD in December 2013.