Planet of Fire ( TV story ) Planet of Fire was the fifth story in season 21 of " Doctor Who " . It was the penultimate adventure to regularly feature Peter Davison as the Fifth Doctor . The story was notable for the departure of Vislor Turlough , the destruction of Kamelion and the introduction of Peri Brown . It was Peter Grimwade ' s final script and Fiona Cumming ' s last director ial turn for the programme . For Turlough ' s last story , it was decided that his mysterious past , outlined in " Mawdryn Undead " , should be explored . Exteriors were shot on location in Lanzarote in the Canary Islands . The location was chosen after Cumming promoted it with photos from her holiday . Grimwade decided to use the island for multiple settings and the island ' s volcanic landscape also doubled for the planet Sarn . Grimwade had trouble writing for the setting , having never been there . John Nathan - Turner denied his request to accompany the select members of the crew to the island . ( INFO : " Planet of Fire " ) Synopsis . The Master re - establishes psychic control of his robot slave Kamelion . He wants to hijack the Doctor ' s TARDIS to reach the planet Sarn , where he seeks the healing power of Numismaton Gas to restore himself . Once on Sarn , Turlough comes face to face with his destiny . And his death . Plot . Part one . On the desolate volcanic planet Sarn , chief elder Timanov counsels the young Chosen One Malkon on how to act in the wake of increased seismic activity , heralding the imminent volcanic catastrophe known as the Time of Fire . Their god Logar , the devout Timanov warns , is greatly displeased at the number of unbelievers . As the Chosen One – so chosen due to the triangular " Mark of Logar " on his arm – Malkon has sole authority to assign heretics to burn in the Cave of Fire and thereby appease their god . Malkon doubts his resolve to condemn unbelievers to death . Meanwhile two such unbelievers , Amyand and Roskal , scale the forbidden Mountain of Fire – believed to be Logar ' s dwelling place – and find the crater at the top empty . Now fully convinced that Logar is a myth , they return to the village to spread the news . As the Fifth Doctor muses bitterly about Daleks and the departure of Tegan , Kamelion ' s agonised cries are heard from an adjoining room . He has linked himself to the TARDIS data core . The TARDIS then picks up a distress signal ; Turlough recognises the pattern and is sufficiently dismayed that he disables the communicator to stop the signal . The TARDIS coordinates have been changed , apparently by Kamelion , and they are en route to the source of the signal , the island of Lanzarote . American archaeologist Howard Foster and his team are trolling the nearby seabed for ancient relics . Among the artefacts they pull up is a strange , anachronistic metal object also bearing the Mark of Logar . Howard ' s restless stepdaughter Peri Brown , accompanying the expedition while on holiday from university , is bored and wants to travel with her friends to Morocco . Howard appears to relent , but strands her on the boat to make her miss her flight . Peri is furious at Howard , but finds his wallet full of money and an alien object Howard had fished out of the lake . She thinks it may be worth some money . Peri strips to her bikini and stuffs the artefact , Howard ' s money and her clothes into a plastic bag . She then jumps in the sea and begins swimming to shore . While the Doctor explores the island trying to find the source of the signal , Turlough has returned to the TARDIS , where he finds Kamelion at the console trying to establish contact with an unknown entity . Turlough overloads the console to disable him out of anger , thinking the signal may be from Trion . On the monitor , he sees Peri struggling in the water and beginning to drown . He runs out of the TARDIS , strips to his bathing suit , jumps into the water and swims out to her . He pulls her ashore and takes her to Tegan ' s old room to recuperate . He finds the alien artefact in the bag , pulling up his sleeve to show that he too bears the Mark of Logar on his arm . While Peri tosses and turns , muttering incoherent apologies , Kamelion seizes on her psychic impulses and transforms into Howard . The Doctor has traced the signal back to the artefact now in the TARDIS . The doors close and the TARDIS takes off automatically , apparently returning the object to its planet of origin , Sarn . Kamelion enters as Howard , but his mannerisms are like someone else ' s . After putting her clothes back on over her swimsuit , Peri enters the control room , confused as to where she is . In the great hall on Sarn , Timanov and Malkon attempt to quell the citizens ' unrest due to the impending Time of Fire . The arrival of Amyand and Roskal with the news of their findings causes even more disruption . A desperate Timanov calls for a sign from Logar , and a burst of flame from the Cave of Fire is the apparent answer . Timanov seizes this as a call from Logar to burn the unbelievers . Just then , a lookout announces the arrival of the TARDIS , describing it in a way that corresponds with their legend of the Outsider , a representative of Logar . Timanov urges Malkon to condemn the heretics , but he hesitates . Once the Doctor and Turlough leave to explore , " Howard " announces that contact has been established , and that he now has control of the TARDIS . As he laughs maniacally , his features change into that of the Master before Peri ' s horrified eyes . Part two . The Doctor and Turlough explore the apparently deserted village square finding the triangular pattern , which Turlough identifies as the Misos Triangle , etched on a column . The Misos Triangle is an emblem of Turlough ' s home planet , Trion , but he is not forthcoming with further details . They do not notice another TARDIS materialising nearby . The Master ' s control of Kamelion is tenuous , and the shape - shifting robot momentarily regains self - control . He removes the TARDIS ' s comparator and urges Peri to give it to the Doctor , but then loses his self - will and his form shifts back to the Master . He pulls her out into the village square towards the Master ' s TARDIS , but a sudden tremor knocks it over , door - side down and a large rock falls hitting Kamelion causing him to fall over which allows Peri to escape into the desolate wilderness . The Master , trapped inside his TARDIS , orders Kamelion to pilot the Doctor ' s TARDIS inside his own , but without the comparator it won ' t function . The unbelievers storm the great hall , having found and befriended the Doctor and Turlough , displaying the travellers as the Outsiders . Turlough discovers the Misos Triangle on Malkon ' s arm , showing his own . He is convinced that the relics in the hall are from his father ' s ship , and that Malkon might be his younger brother . Malkon describes how he was found in the Place of Fire as an infant , and Turlough convinces him to take him there , where they find the wreckage of a crashed spaceship . They encounter Peri , who had been wandering lost since eluding the " Master " . When Turlough learns that the Master is involved , they dash back to the village to warn the Doctor . The Doctor , however , finds himself at the mercy of Timanov and his own Outsider , the Kamelion / Master . Under the " Master ' s " sway , Timanov orders the sacrifice of the unbelievers to the flame . The " Master " demands the return of the comparator , which the Doctor doesn ' t have , as his new allies are pushed toward the mouth of the Cave of Fire . Part three . Malkon demands that the execution cease , but is shot down in the ensuing struggle . Timanov has the unbelievers and the Doctor locked into the cave with the flame . Turlough uses a Trion relic to remotely disable the sacrificial flame , which Timanov shows as a sign of displeasure from Logar at Malkon ' s apparent assassination . Still fooled by the " Master " , Timanov leads a team of Sarns in helping to shift the Master ' s TARDIS , but once upright , the " Master " pulls Peri inside and dematerialises . Turlough arrives and releases the Doctor and the unbelievers from the cave . The Doctor struggles to figure out why the Master is on Sarn , and how to rescue the citizens from the impending doom of the volcanic eruption . He also reasons that the Trions had a more productive use for the Cave of Fire than mere sacrifice . Timanov speaks of a time when he was young , and he encountered Logar who took him to a bath of blue flame that rejuvenated him . The Master ' s TARDIS materialises in a control room deep below the volcano . The " Master " enlists Peri ' s assistance , on pain of death from his Tissue Compression Eliminator weapon , in controlling the machinery there to harness the power of Numismaton Gas , which is indeed a bright blue flame renowned for its healing properties . The Doctor takes advantage of the presence of the Numismaton flame to heal the ailing Malkon in the Cave of Fire . Eluding the Kamelion / Master and ducking into the Master ' s TARDIS , Peri locates what she reasons must be Kamelion ' s control box . Lifting the lid , she finds the Master lurking within , reduced to mere inches in height . Part four . The Master , having accidentally shrunk himself while attempting to upgrade his TCE weapon , seeks the power of the Numismaton Gas to restore himself . He constructed the control box to re - establish contact with his slave Kamelion to help him reach Sarn . Peri accidentally knocks the Master ' s control box over which allows the Master to escape into his TARDIS . Peri tries to track him down and swat him with her shoe , but he escapes and hides in the TARDIS console . There , he taunts Peri and shorts the controls to open the TARDIS door . Peri runs out and into the wilderness The Doctor and Amyand , with Peri ' s help , have reached the Numismaton gas control room . They find protective metallic suits which correspond with the traditional image of Logar . The Doctor realises that the Trions have used the control room to regulate the seismic activity , but the impending eruption will be too big to control . The Doctor sends Amyand back to the ruins wearing the only remaining suit . Kamelion pilots the Master ' s TARDIS into the blue flame and brings out the control box , bearing the Master within . As Kamelion advances menacingly on the Doctor with the TCE , he overloads the gas control circuitry to give Kamelion a near - fatal " heart attack " . Kamelion , now freed from the Master ' s control , begs for destruction , and the Doctor complies with the TCE . The Master is restored to full height by the Numismaton gas , and gleefully describes the tortures that await the Doctor at his hands . But the Doctor ' s fiddling with the controls cuts off the gas , leaving the Master to burn in the full power of the naked flames . The Master ' s pleas for mercy go unheeded , and the Doctor watches as his enemy is apparently consumed by fire . Turlough , despite his status as a Trion political prisoner , swallows his pride and manages to re - activate the communication system in the wreckage of his father ' s ship , summoning a Trion rescue ship to pick up the Sarn survivors . Timanov , humbled by his easy manipulation by the Master in the name of his god , declines rescue and opts to perish in the ensuing volcano . Acting on instructions from the Doctor , Turlough programs the TARDIS to rescue the Doctor and Peri from the gas control room before it is destroyed . The Trion captain Lomand informs Turlough that due to general amnesty , his exile has been lifted and he is free to return home . Turlough thanks the Doctor , who understands Turlough ' s reasons for wanting to return to Trion , for everything and the two warmly bid each other farewell . Peri , on the other hand , asks to travel with the Doctor for the remaining three months of her vacation . The Doctor agrees , and he welcomes her aboard the TARDIS as it takes flight .