The Keeper of Traken ( TV story ) The Keeper of Traken was the sixth story of Season 18 of " Doctor Who " . It was the first story to feature Sarah Sutton as new companion Nyssa , and featured the return of the Master after a long absence , here played by Geoffrey Beevers and ( briefly ) Anthony Ainley . It is also the first story in what is sometimes referred to as " The Master Trilogy " . In this story , the Master assimilated a new body to replace the one that was withering , and thus changed physical appearance without the aid of regeneration . Anthony Ainley would now portray the Master until the end of the classic series with his substitute body . Synopsis . The Doctor and Adric learn from the wizened Keeper of Traken that a great evil has come to his planet in the form of a Melkur - a calcified statue . The Keeper of Traken is nearing the end of his reign and seeks the Doctor ' s help in preventing the evil from taking control of the bioelectronic Source that is the keystone of the Traken Union ' s civilisation . Plot . Part one . In the TARDIS , the Fourth Doctor and Adric have arrived back in N - Space near the star Mettula Orionsis , home to the Traken Union , famous for its universal harmony . Suddenly they find themselves in orbit of Traken , and the figure of an elderly man on a throne appears within the console room . The Doctor identifies him as the Keeper of Traken . The Keeper reveals that he will soon die and have to pass on his powers to a successor . He asks the Doctor to come to Traken , but warns him of great danger . On the scanner , the Keeper reveals images of Traken and of the arrival of an evil creature known as a Melkur years ago . The creature ' s baleful influence cannot go beyond the groves , and it becomes calcified . A young Trakenite woman called Kassia is seen pitying it . On present day Traken , Consul Tremas is marrying Kassia . Tremas and Kassia enter the Keeper ' s chamber to receive his blessing . Tremas is the Keeper ' s named successor . In the grove , Kassia tends to Melkur for what is supposed to be the last time . She pours out her heart to the inanimate statue about her concerns , that once Tremas becomes Keeper , he will be taken from her . A voice is heard emanating from Melkur echoing her word " soon " . A short time later , Fosters find a body outside the Grove and the Consuls are summoned to a meeting by Kassia . Tremas scans the area , but the readings are off the scale of his instrument . He says that it means some force is taking control of Traken . Believing the man to have been murdered , Kassia says that the great danger necessitates that the Fosters be armed , but the Consuls cannot agree among themselves and summon Proctor Neman . The TARDIS emerges in the Grove , opposite to the Melkur statue . As the Doctor and Adric exit the Grove , they are surrounded by armed Fosters . The consuls vote to summon the Keeper , just as the Doctor and Adric are brought before them . Neman and the other Fosters are sent to check the presence of the Doctor ' s craft in the grove , but before they arrive , red light is seen shooting from the Melkur ' s eyes towards the TARDIS , causing it to disappear . Melkur is later seen striding from the Grove towards the Court room . The Consuls ask about the identity of the Doctor and Adric , and Melkur stands at the doors of the room seen only by the Keeper , its eyes glowing red . The Doctor asks the Keeper to identify them , but he cries out , " Evil ! The sanctum is invaded ! . . . Evil , infinite evil ! " The Keeper then vanishes , and Melkur moves out of sight . The Consuls and the Fosters then point their weapons at the Doctor and Adric , and close in on them . . . Part two . Kassia describes the Doctor and Adric as creatures of evil before becoming overwhelmed and fainting . Seeing Tremas ' s instrument , the Doctor says that he could use it to detect the high energy beam used to attack the Keeper . Meanwhile , Melkur is seen attacking Fosters with lasers shooting from its eyes . Tremas speaks up for the Doctor and Adric , and invokes Consular privilege to protect them . Kassia is particularly displeased . Consul Seron says that should they breach any law , Tremas ' s life will also be forfeit . Meanwhile Kassia rushes to Melkur and starts hiding the bodies of the Fosters . The following day , Tremas and the Doctor go to the Grove to search for the TARDIS . Meanwhile , Adric and Tremas ' s daughter Nyssa are conducting a Fourier analysis of the energy readings . In the Grove , Kassia is seen again conversing with Melkur . He gives her a band and asks her to wear it as a token of her allegiance , and she places it around her neck . When the band glows red , Melkur commands her to go forth and be its eyes and ears . Kassia informs it that Seron will enter rapport with the Keeper instead of Tremas , but Melkur is not concerned . Tremas and the Doctor enter the Court room , where they see Kassia emerging from the source chamber in some sort of trance . When she has gone , they descend into the source chamber and enter the grove through a secret entrance . There , the Doctor realises that the TARDIS is in fact present in the Grove , but has been displaced in time . Later , the Source manipulator activates ; the Keeper is being summoned — it is Seron ' s rapport . Watched by Kassia , Seron is enveloped in a column of light . Kassia ' s band and eyes glow , and she shoots laser beams , killing Seron . At that moment , Tremas arrives , but as the other Consuls arrive Kassia declares that Seron was dead because he was rejected by the Keeper . She orders the Fosters to seize Tremas , the Doctor and Adric , but they flee to the grove , where they are found by Kassia and the Fosters , who catch them in a net . Kassia returns to the Melkur and tells him that the deed is done . However , he answers back , " Oh , no Kassia . It is only beginning . . . " Part three . Tremas , Adric and the Doctor are placed in a cell in the penal wing by the Fosters . In the grove , Melkur informs Kassia that Tremas will continue to live as long she continues to obey , and that she must become the next Keeper . Tremas informs the Doctor that Melkur could not come in contact with the Source , as the bio electronics only permit access to a Trakenite . Kassia meets with Katura and Luvic to persuade them that she should be the Keeper - nominate , which they readily do . Meanwhile , Nyssa attempts to get past Neman to see her father . When he will not budge , she shoots him and another guard with a green energy beam . She proceeds to the cell and frees the Doctor and the others . When Kassia finds the stunned Neman , she furiously orders him to search the sanctum and the Grove . The Doctor goes to Tremas ' s quarters , hoping that they have already been searched . The Doctor asks him if he has the master plans for the source manipulator . The Keeper is dying , and Kassia is summoned by Katura and Luvic . The Doctor and the others try to get to the TARDIS , but are caught in the Grove by Neman and the Fosters . Neman informs them that the Keeper - nominate has sentenced them to death , but a sudden thunder storm terrifies the Fosters and they flee before carrying out the execution . Kassia enters the Sanctum at the moment of the Keeper ' s death , and seats herself on the Keeper ' s throne . Inside Melkur , a hideously deformed figure is seen , while behind him is a black wall with roundels . . . The Melkur statue dematerialises from the grove with a TARDIS - like sound . As Katura and Luvic prepare to use their Consular rings to connect Kassia to the source , the Doctor bursts into the chamber and pleads with Katura not to complete the transition , but she ignores him . Kassia screams in agony , and disappears . The Melkur statue materialises in her place . . . Part four . Melkur commands Neman to confine the Consuls to their quarters . As he does so he begins to fade from the throne before disappearing . The Doctor and Tremas discuss how they might be able to defeat Melkur before he has complete access to the Source . They do not have the five Consular rings , but with the Source manipulator blue - print , the Doctor thinks there may be a way . Melkur dispatches Neman , now adorned with a control band , to secure the blue print document . He enters Tremas ' s quarters , and asks for the blue print to be handed over . The Melkur statue materialises within the room , and when Tremas refuses to release the document , Melkur shoots energy beams from his eyes at him . The Doctor releases the document , and Melkur burns it with its energy beam . The Doctor knocks Neman and the Fosters ' heads together , and retrieves Tremas ' s Consular ring . Nyssa and Adric complete construction of a servo - shutdown , with which they can sabotage the source manipulator . The Doctor goes to the sanctum , and prepares to try to break the encryption of the Source security system . Nyssa and Adric enter the Source manipulator chamber and prepare to attach the device . Tremas tries to make a defiant stand against Melkur , but Melkur mentally controls him . Neman is brought forth and hands his weapon to Tremas . Under Melkur ' s willpower , Tremas shoots down Neman . Melkur outlines its plans of conquest . The Doctor is drawn within the Keeper ' s inner sanctum , before both he and the Melkur disappear . Inside Melkur , the Doctor immediately recognises the disfigured creature as . The Doctor is paralysed when the Master keys his TARDIS ' systems to his bio rhythms . The Master explains that he is nearing the end of his twelfth regeneration , and that with the powers of the Keeper of Traken he can extend his life beyond this final limitation of a Time Lord . Just as he is about to attack the Doctor to take his body , the servo - shutdown begins to destabilise the Source . The Doctor , able to move once again , smashes through a glass panel to escape . With the encryption broken , Adric ' s sabotage of the Source is reversed . Luvic runs to the throne to become the new Keeper before the Source dies . Adric and the Doctor return to the TARDIS . As things settle down on Traken , Tremas investigates a mysterious longcase clock . When he touches the clock face , he is transfixed and the door of the clock opens . The Master emerges and merges with Tremas . . . " a new body at last . . . " . Laughing , the newly - rejuvenated Master enters the clock , which is in fact his TARDIS . Seconds after the Master ' s TARDIS has dematerialised , Nyssa comes looking for her father . She calls to him , but there is no answer . . . Home video and audio releases . DVD releases . This story was released on DVD together with " Logopolis " and " Castrovalva " as part of the " New Beginnings " DVD box set . It was released : Part four is extended slightly to incorporate a dedication to the memory of Anthony Ainley , who died between recording his commentary and the DVD ' s release . The dedication includes a brief outtake of Ainley from his recordings for the videogame " Destiny of the Doctors " . The clip ' s inclusion is technically an easter egg as it isn ' t listed on the DVD menus or cover . Special features : Notes : VHS releases . This story was released on VHS in June 1993 in the UK , in September 1993 in Australia and in February 1994 in the US .