The Monster of Peladon is the fourth serial of the 11th season of the British science fiction television series Doctor Who, which was first broadcast in six weekly parts from 23 March to 27 April 1974.
On the planet Peladon a power struggle is in place between the trisilicate miners and the ruling class, with miners under the leadership of Gebek and hot-headed Ettis calling for improved conditions. The planet’s ruler Queen Thalira, daughter of the late King Peladon, is sympathetic, but knows her planet is vital to supply the war effort of the Galactic Federation of which it is a member. The Federation is in conflict with the warlike Galaxy Five confederation. The miners become concerned when a vision of Aggedor, the royal beast, starts appearing in the mines and killing miners, including the alien engineer Vega Nexos. Chancellor Ortron tries to convince the Queen this is a sign of displeasure at the alien presence on the planet, but she remains unconvinced.
Another alien presence reaches the Citadel: the TARDIS, bearing the Doctor and Sarah Jane Smith. He recalls his visit to Peladon fifty years earlier when the planet joined the Galactic Federation, and is pleased to find a familiar face in Alpha Centauri, the Federation Ambassador. The Queen knows of the Doctor from her father and enlists his support in trying to find the cause of the manifestations of Aggedor. He guesses someone is deliberately trying to interrupt trisilicate production, and they seem to have succeeded when the miners decide to strike. Ettis then leads an attack on the Federation armoury and gets weapons for the striking miners. This looks like damaging trisilicate supplies even further, so Engineer Eckersley, a human in charge of the refinery, coaxes Alpha Centauri to send for Federation troops to help restore order.
Both the miners and the Pel leaders are unhappy with the notion of Federation occupation, especially when the Ice Warrior force displays its ruthlessness in shooting down Pels. The sole concern of the force leader, Commander Azaxyr, is to maintain trisilicate production. There is now a realignment in Pel politics: Ortron and Gebek join forces in seeking to rid the planet of the Martians. Ettis, however, has become crazed and is killed trying to blow up the Citadel. The Ice Warriors now impose martial law on the capital, imprisoning the Queen and her courtiers, and even killing Ortron when he tries to flee.
The truth is now revealed: Azaxyr and Eckersley are both Galaxy Five agents and have engineered the crisis and occupation as a means to control the trisilicate supply. The Aggedor apparition was just an image created to support the panic. Gebek now leads the Pels in a final assault on the Ice Warriors, and Azaxyr and the other invaders are killed. Eckersley himself is killed by the real Aggedor when he attacks the Queen, though sadly the beast dies in the process. News now reaches Peladon that Galaxy Five has capitulated, its Peladon stratagem exhausted, and Queen Thalira seeks to repair the society when she appoints Gebek her new Chancellor. As ever, the Doctor and Sarah slip away quietly.
This story is a sequel to The Curse of Peladon, and features the same themes of a culture steeped in deep seated traditional beliefs facing the shock of new and alien ideas. Sarah Jane refers to these events in the serials The Temptation of Sarah Jane Smith and Death of the Doctor in the spin-off series The Sarah Jane Adventures.
The Virgin New Adventures novel Legacy was the first continuation of Peladon's narrative arc in the series' tie-in media. Featuring the Seventh Doctor, it is set fifty years after Monster of Peladon, book-ending the world's involvement with the Federation.
A potentially divergent continuity established by Big Finish's audio plays has the Third Doctor returning to the planet again in the Companion Chronicles story The Prisoner of Peladon, which features David Troughton reprising his role as King Peladon.
The Fifth Doctor returns to Peladon in the Big Finish audio play The Bride of Peladon. This story has a number of thematic similarities with the original Peladon story, and features the departure of the character Erimem.
The mineral was named Trisilicate because Barry Letts saw it listed on the back of a tube of Boots Toothpaste as one of the ingredients.
The character played by Roy Evans is credited as 'Miner' on-screen, but is named as Rima in dialogue – and is also credited as such in the Radio Times.
Both Alan Bennion and Sonny Caldinez had regularly appeared as Ice Warriors in their previous appearances, with Bennion playing different "Ice Lord" characters in both The Seeds of Death and The Curse of Peladon, while Caldinez had appeared in all three preceding Ice Warrior serials. Additionally, Caldinez had played the mute Kemel in The Evil of the Daleks.
In The Television Companion (1998), David J. Howe and Stephen James Walker noted that the serial failed to be a fresh sequel to The Curse of Peladon because it simply carried many of the same characters and story points, and that it was also unlikely that some of the same characters would still appear fifty years later. They also wrote that the story "drags awfully," and, aside from the Ice Warriors, they criticised the supporting characters. In 2010, Mark Braxton of Radio Times said that there was a prevailing sense of déjà vu throughout The Monster of Peladon. While he noted that story had its moments, he criticised the casting and felt that Pertwee and Sladen continued to lack rapport. DVD Talk's John Sinnott gave the serial three out of five stars, feeling that the shift in tone halfway through kept interest while the plot was similar and the subplots were repetitive.
A novelisation of this serial, written by Terrance Dicks, was published by Target Books in December 1980.
The serial was released on VHS on 27 December 1995. It was released on Audio CD with linking narration by Elisabeth Sladen, on 3 March 2008. The Monster of Peladon was released on DVD on 18 January 2010 in a boxset entitled 'Peladon Tales', along with The Curse of Peladon. This serial was also released as part of the Doctor Who DVD Files in Issue 125 on 16 October 2013.