The Mutants ( TV story ) The Mutants was the fourth story of season 9 of " Doctor Who " . Its narrative inspiration was very similar to that of " Colony in Space " . Whereas Malcolm Hulke had based the earlier story on the struggle of Native American s against Europe an settlers , here Bob Baker and Dave Martin explicitly based their story on South Africa and the segregationist policy of , which had also inspired Ian Stuart Black ' s " The Savages " . By the recording , however , director Christopher Barry had de - emphasised the political allegory in favour of the story ' s science fiction al elements . One such element came from an unused 1966 Barry Letts story submission , itself entitled " The Mutant " . Forming the main plot of the later episodes , this Letts - inspired subplot focused on a species maturing in radically different physiologic phases , like a butterfly . Synopsis . The Time Lord s send the Doctor and Jo on a mission to deliver a sealed message pod to an unknown party aboard a Skybase orbiting the planet Solos in the 30th century . They are caught quickly in a power struggle between the cruel Marshal of Solos and the young Solonian Ky over the future of Solos — a future that hinges on the contents of the message . Plot . Episode 1 . On the polluted world of Solos , an old man flees through the desolate remains of a forest . Screaming , " Mutt ! Mutt ! " , the Marshal of Solos chases the old man , followed grudgingly by Stubbs and Cotton . Pausing to pick up the Marshal ' s dropped oxymask , essential in the toxic Solonian air , Stubbs and Cotton briefly lose their commanding officer in the thick mist . They find him standing over the corpse of the old man . The dead Solonian has jagged deformities on his back . The Marshal orders his men to log it : another dead Mutt . Back on 20th century Earth , the Doctor and Jo are interrupted by the sudden appearance of a message pod from the Time Lord s . His TARDIS is already programmed with its destination and , despite his objections , Jo joins the Doctor as it sets off for Skybase One in orbit of Solos . Arriving in the Skybase ' s broom cupboard , the Doctor explains to Jo that they are at the end of the Earth Empire ' s reign . At the Skybase ' s Transmat facility , Solonians are beaming up from the planet to attend a conference with the Overlord s , the planet ' s colonists from Earth . Ky arrives and is greeted by Varan . The greeting is anything but friendly . Ky makes it clear he considers Varan the lackey of the Overlord s . They argue over the status of the Mutts . Varan considers them a disease to be weeded out . Ky believes it murder of his people . The argument escalates . Ky accuses the Overlords of polluting his world and enslaving his people . Varan and he nearly come to blows . The fracas is prevented only when the group is shepherded to decontamination ( save Varan , who is sent to see the Marshal ) . Only one guard and one Solonian , Varan ' s bodyguard , remain in the Transmat lobby . The guard notices the Solonian is hiding his hand . Grabbing the limb , the guard sees it is green and scaled . He screams for help , only to be killed by the mutated Solonian . In their private conference , Varan is furious with the Marshal that Ky has been allowed to attend the conference . Wiser than his native representative , the Marshal insists that Ky not become a martyr . He has a plan for Ky and needs a trustworthy Solonian from Varan . The Doctor uses his sonic screwdriver to burn out the lock on the cupboard doors , breaking and entering into Skybase One . This intrusion is detected by a communications operator and a klaxon whines . " Attention . Attention . Computer confirms door malfunction in storage area four . " Jo responds , " That ' s us . " The Doctor replies , " Yes , I know . I ' m not sure I like being described as a malfunction . " Two guards , Stubbs and Cotton , are in the middle of a chess game during their break . Responsible for checking the status of the base , Stubbs thinks they should deal with the door malfunction , but Cotton talks him out of it , reasoning that they just got back from a " Mutt " hunt and should put it off until morning . Cotton also mentions that their superior , " His Nibs " , the Marshal , won ' t be " rushing about tonight " . The Marshal explains to Varan that he needs someone completely trustworthy under his wing . Varan assures him all his warriors are loyal to him and will fight to the death if he orders so . Satisfied , the Marshall gives him a pass . Varan approves of it , but the Marshal is concerned Ky won ' t be as enthused about accepting a handout from a human and sends him off with the request that he will want to see the dependable Solonian man he offered to recruit . When Varan has exit the Marshal ' s office , his true , duplicitous nature shines through in a moment of solitude . The Marshal takes a moment to recognise how gullible Varan was , muttering to himself , " The fool . " As they explore the Skybase and venture deeper into the corridors , the Doctor and Jo find nobody around . The Doctor calls out , hoping to get a reply . When that merits no answer , they wander into storage area 3 . The Doctor tries to open a closed door panel , but it remains shut . He pulls out his sonic screwdriver again and begins disabling the lock again . Just as he remarks that they " can ' t wander around all night without nobody noticing " , they are attacked by the mutated Solonian bodyguard . Jo spots him moments before the Doctor cracks the door lock . The door shuts on the bodyguard ' s arm and traps him in place . The Doctor tries to prevent him from forcing his way out by holding the door hatch closed . A second warning is issued by the comm operator . Instead of a passive notification , this one is an urgent warning demanding action at once . Stubbs and Cotton are dispatched to investigate the door ' s failure , no longer given the leniency to shirk off their duties . Stubbs instantly regrets listening to Cotton when they should have gone to investigate the first malfunction and how much trouble this bungle has caused them . Finding the Doctor and Jo under attack , they order them to get away from the door . The Doctor protests that doing so is foolish because the man who attacked them could quickly overpower them with his mutated hand . Cotton has little other choice but to shove the noncompliant Doctor and Jo away from the door . Once the bodyguard charges through , Stubbs doesn ' t hesitate to shoot him , killing the Solonian . He delivers a report into his communicator that he and Cotton have investigated the storage malfunction , coming into contact with a mutant native and destroying it . He also declares that they have found two " non - personnel " in a restricted area , which will now be held , presumably until they are identified . Casual at performing his job , Stubbs is friendly enough to greet the Doctor and politely asks him and Jo if they will please come with them to reception . The Doctor surmises they don ' t have a choice to refuse and have to follow the guards . Stubbs and Cotton take the Doctor and Jo into custody . The Doctor questions Stubbs about reporting a mutant native , and Stubbs confirms this is right . The slain Solonian can be seen with ridges protruding down his back along with the mutated arm . With Varan ' s bodyguard dead and two trespassers found , the Marshal is being dressed down by his superior , an Administrator from Earth . The Administrator has a bombshell to be dropped at the conference . The Empire is pulling out of Solos . Earth is near economic , political and environmental collapse . An empire is a luxury they can not afford at this point . The Marshal is livid . He believes this to be all the more reason their colonisation of Solos is imperative . The Administrator scoffs . It would require genocide of the already mistreated Solonians . The decision has been made . Ky will be getting all he demands . As the Administrator leaves the room , the Marshal summons Varan again . After waiting in the reception room overnight , the Doctor and Jo await the arrival of officials . Wearing sunglasses , Jo peers out through a porthole and remarks that they can now see the planet Solos in daylight but is dismayed by how " grey and misty " it is compared to Earth . The Doctor regretfully informs her that there is no difference in forethought . This is a time period where the people are used to the crumbling thirtieth century Earth empire , by which time the people of Earth have tarnished the beauty of the once blue planet with over - industrialisation , making even more grey and misty than Solos . He describes 30th century Earth as " land and sea alike , all grey . Grey cities linked by grey highways across grey deserts . " Jo is appalled to learn this . The Doctor grimly reminds her how humanity can go too far with its exploits . " Slag , ash , clinker . The fruits of technology , Jo . " Before heading to the conference , the Marshal and Administrator stop to interrogate Jo and the Doctor . However , the Doctor has had time to submit statements which explain their intentions for coming to Skybase One , tactfully leaving out the part that they arrived from an entirely different time period . The Doctor says they came to the Skybase from Earth , sent by Overlord Centre . The Adminstrator sees the Doctor is referring to the council on Earth but is confused by their arrival because the council ' s interest in Solos has ended . Spinning a yarn , the Doctor has him think the council thought otherwise when they sent him and Jo up to the Skybase . The Marshal , an insidious man at heart , is quick to suspect them out of paranoia that his underhanded dealings have been caught , and these two strangers threatening to expose him as a crook . The Administrator is more sanguine . He tries to allow the Doctor to speak and be reasonable in the company of an evidently perturbed and vocal Marshal , but to no avail . The Marshal drills the Doctor with questions about his departure time . When the Doctor gives him a hazy reply , the Marshal is convinced he ' s lying altogether , more so because he lacks a clearance pass . When the Doctor argues why it is important he knows how they got to the Skybase , the Marshal browbeats him and concludes he and Jo are from Solos . Exasperated , the Doctor reasons with him that they had a mission to give someone on board Skybase One a container by presenting both the Marshal and the Administrator with it . However , it refuses to unlock for anyone . Since it will only open for the person it is meant for , neither of them are supposed to possess it . The Doctor is unable to prove it is safe because he cannot open it , either . The Administrator perceives the offering of the sealed box as a joke , and the Marshal believes it can be opened with force . He snatches Stubbs ' s gun and attacks the container , shooting it twice . It huffs with smoke from the laser impacts without even leaving a scratch on it . Infuriated , the Marshall thinks it is the handiwork of saboteurs in league with the Mutts . Annoyed , the Doctor snips , " Oh , don ' t be a fool . If we were saboteurs , that ' d be a bomb , and thanks to you we ' d all be blown to smithereens by now . " Jo also comes to the Doctor ' s defence when the Marshal is sceptical they ' re being truthful about their mission , but it still doesn ' t get through to him . After touting multiple wild accusations toward the Doctor and Jo , the Marshal ' s innate fear of being caught finally causes a slip of the tongue . In an irrational blurt , he believes them spies from Earth , special agents from the council sent to check up on him . Cotton enters , telling the officials the Solonian delegates are ready to see them . The Doctor tries to have the Marshal take the box with them in case the person who is intended to have it is present at the conference . Stubborn and snide , the Marshal dismissively says there are " far more important things " to be dealt with than a simple box or two suspicious occupants of Skybase One . Whoever they are , they can wait until after the conference with the Solonians . Regardless , he leaves Stubbs posted with the Doctor and Jo and makes it clear he doesn ' t want them to leave Stubbs ' s sight , not willing to turn a blind eye at the unwelcome pair on his base . As the representatives of Solos assemble , the Marshal passes a small device to Varan . Varan passes it to his son . The conference is being telecast throughout the Skybase . The Administrator begins his speech to the Solonians . Watching the telecast together , the Doctor uses the distraction to overpower Stubbs and make his way to the conference with the message pod . The Administrator ' s speech , though intended as conciliatory , comes off as condescending and bombastic . Ky disrupts it several times . As they shout at each other , Varan ' s son shoots a dart from the device . It strikes the Administrator in the neck . He drops dead . The conference erupts into chaos . The Marshal orders Ky ' s arrest . He flees the conference chamber , nearly colliding with the Doctor just outside the door . The momentary contact has an immediate effect on the message pod ; it begins to open for Ky , its intended recipient . Despite the Doctor ' s protestations , Ky grabs Jo as a human shield and continues to run . He pulls her into the Transmat as the Marshal orders his men to open fire . Their blasters turn the Transmat into a shower of sparks . . . Episode 2 . The smoke clears . The Transmat chamber is empty . The Marshal points out Jo ' s safety may be short - lived . She has no oxymask , nor shall she long survive on Solos without one . At the Transmat ' s ground station , Ky and Jo materialise amidst klaxons . Dodging fire from the ground station ' s lone guard , they escape through an airlock onto the polluted world . They are pursued by more troops , but this is to their advantage . Ky overpowers one and takes his oxymask . High above in the Skybase , the Marshal has assumed command in the wake of the Administrator ' s death . He strikes a bargain with the Doctor — open the message pod , and the Marshal ' s men will try to save Jo . The Doctor agrees reluctantly . He is escorted to the Skybase ' s lab . The Marshal assigns his own scientist , Jaeger , to assist . Jaeger is put out by the distraction from his own work on the Solonian atmosphere but complies . The Marshal turns to the loose ends of the assassination . He kills Varan ' s son with the dart - gun and tries to do the same to Varan himself . Varan escapes , but the Marshal declares him a Mutt and orders him captured and executed . With Jaeger ' s reluctant help , the Doctor builds a particle reversal device to see the contents of the message pod . Stunned when the process works , Jaeger realises that particle reversal could convert the Solonian atmosphere to a more habitable one in days . Seeking shelter in a cave , Ky explains his people ' s suffering to Jo . Meanwhile , Stubbs is joined by the Doctor in the search for Varan . They think they have him cornered , but Varan disarms Stubbs and nearly kills him . The Doctor ' s crack shot with a blaster takes the blade out of Varan ' s hand . Having learned the truth about the assassination from Varan , Stubbs is now the Doctor ' s ally , albeit clandestinely . They lie to the Marshal , claiming Varan is dead . The Marshal , meanwhile , has coaxed Cotton into lying also , corroborating the Marshal ' s claim that Jo has been found and is in a hospital on Solos . Their deceptions at an impasse , the Marshal shuffles the Doctor off to Jaeger ' s project to alter Solos ' atmosphere . Jaeger uses the Doctor ' s outrage at the proposed method — rockets launched into the atmosphere , killing all the Solonians as a " side effect " — to manipulate him into offering his particle reversal method as alternative . Cotton speaks to the Doctor discreetly . He explains that Stubbs has brought him in on their side and tells him the truth about Jo . The Doctor and Cotton devise a method to get the Doctor off the Skybase . Then the Doctor turns the tables on Jaeger , using his enthusiasm for particle reversal to make him a patsy for the escape . Stubbs informs Varan of the plan to get off the Skybase . Though suspicious , he appears to agree . The Doctor overloads the Skybase power , stunning Jaeger . He makes his way to the Transmat , only to be grabbed by Varan . With his blade at the Doctor ' s throat , he growls , " Die , overlord ! " Episode 3 . With Varan literally at his throat , the Doctor transmats to Solos . As the two emerge from the transmat chamber , the Doctor incapacitates his assailant with some Venusian aikido . He extracts Varan ' s word as a warrior that he will take the Doctor to Ky . Despite the onset of a firestorm in the sky ( a " side effect " of the Marshal ' s manipulation of the atmosphere ) , they set out into the Solonian night . Elsewhere on Solos , Ky and Jo watch the same firestorm before a group of agitated Mutts forces them to retreat deeper into the cave . After expressing his frustration with Jaeger by means of a cathartic yelling session , the Marshal orders his scientist to go ahead with the original , more genocidal atmosphere modification plan . He summons Stubbs and Cotton to his office . They are understandably apprehensive , what with their recent treason . They are dressed down , but the Marshal does not consider them traitors , merely incompetent . He sends them down to Solos to pursue the escaped Doctor and Varan , flushing them out of the cave s with gas grenade s . Varan ' s tracking leads them to Ky and Jo ' s fire . Despite Varan ' s protests that he will go no further , the two proceed deeper into the cave after their quarry . Ky , meanwhile , fends off a mob of increasingly agitated Mutts . The Doctor and Varan ' s arrival helps quell the beastly melee , but Jo has run deeper into the caves . She finds a chamber of light and sound , driving her to unconsciousness . A figure in a protective suit emerges and moves to her side . The Doctor finally gives the message pod to Ky . In his hands , the pod opens , revealing a set of stone tablets . Varan and Ky , expecting weapons , are disappointed . Ky identifies the markings on the tablets as ancient Solonian writing ; no one understands it anymore , as the Overlords have destroyed their culture . Varan storms off , declaring he shall lead his village against their human oppressors . Ky and the Doctor , meanwhile , begin searching for Jo . The Marshal begins deploying his gas bombs . He sends Stubbs and Cotton deeper into the caves after the Doctor . Monitoring them on his radio , the Marshal overhears their friendly greeting to the Doctor , then sets off an explosive to seal them in . Varan returns to his village . It is deserted save for an elderly Solonian in the midst of transforming into a Mutt . He is horrified to see the beginnings of the transformation on his own arm , then hears a voice in his head , telling him to " go to the place of sleeping and light . " As Jo recounts her experience in the mysterious chamber , Stubbs reconnoitres , only to find the caves are sealed and the gas is closing in . . . Episode 4 . The figure in the protective suit emerges again . It gestures for the Doctor and his entourage to follow . It leads them to a lead - lined chamber deep in the caves . " Professor Sondergaard , I presume , " quips the Doctor . While the Marshal orders his men to continue sealing the caves , Sondergaard says Jo wandered into a chamber of intense radioactivity . He believes that , while there are normal changes in the ecosystem as the five - hundred - year seasons change , Jaeger ' s experiments altered the natural balance . The Marshal returns to the Skybase and orders Jaeger to begin the bombardment of Solos with ionisation rockets to change its atmosphere . Below , Ky opens the pod again to display the tablets . Sondergaard tries to translate them . He declares them the Solonian equivalent of the Book of Genesis , but his attempts to scry meaning from them are interrupted by the cave ' s continued collapse . Ky , Jo , Stubbs and Cotton head out to the relative safety of Varan ' s village , while the Doctor and Sondergaard remain to continue the study of the tablets . The Doctor hits upon the meaning of the tablets — a calendar of the five - hundred - year Solonian seasons — and interprets one symbol as referring to the radiation of the chamber . Sondergaard and he set off to explore further . Varan addresses his few remaining warriors . He is interrupted by a report of the approach of Overlords . When Stubbs , Cotton , Ky and Jo arrive , they are ambushed and forced to surrender their guns . Varan declares his plan for revenge , to attack Skybase using his captives as hostages and shields . As they plunge deeper into the radioactive chamber , the Doctor is forced to leave Sondergaard when the radiation overwhelms his suit . At the heart of the chamber , the Doctor finds a glowing statue with a green crystal set in it , which he pockets . He retrieves Sondergaard and leaves the chamber . Aboard Skybase , the Marshal ' s plan is forced to accelerate . An Earth Empire investigator will be arriving shortly . Unbeknownst to him , Varan has already taken a transmat ground station and is beaming aboard . The Doctor tries to analyse the crystal he retrieved , but Sondergaard ' s equipment is too primitive . They , too , set out for Skybase . The launch of the ionisation rockets is imminent but momentarily interrupted when Varan ' s incursion is detected . The Marshal orders the countdown to continue while he assembles a squad to repel the intruders . They ambush Varan ' s warriors , slaughtering them with superior weaponry . The Marshal personally dispatches Varan . Unfortunately , his blaster fire tears a hole in the Skybase ' s hull , blowing Varan out into the vacuum . As the ionisation rockets launch , the Marshal , Ky , Stubbs , Cotton and Jo all cling for their lives as the air rushes out into space . . . Episode 5 . Jo , Ky , Stubbs and Cotton struggle out of the depressurised chamber . They find themselves arrested by the Marshal and facing summary execution . The firing squad takes aim , only to be stopped at the last moment by an irate Jaeger . Unconcerned with the welfare of the Marshal ' s captives , Jaeger is livid that his rocket barrage was a complete failure . Due to poor maintenance and the Marshal ' s unreasonable timetable , the rockets poisoned Solos ' surface rather than ionising its atmosphere . Jaeger mentions the investigator in passing , and Stubbs and Jo drive home the point . Even with them executed , the Marshal ' s men are tired and want to go home . One of them will report the true state of the Solonian occupation . The Marshal seems unconcerned . If necessary , he will blow the investigator ' s ship out of space . Jo bluffs the Marshal , claiming that the Doctor is the investigator ' s advance party . On the planet below , the Doctor and Sondergaard find the bombardment waning but the damage done . The plant life is already contaminated by the ionisation crystals . Sondergaard is too weak to continue , but he insists the Doctor go to Skybase to solve the mystery of the green stone . The Marshal returns to Solos to capture the Doctor personally . He hopes that , with Jo a hostage , he can persuade the Doctor to use his particle reversal techniques to clean up the environmental mess on Solos before the investigator arrives . The troops track the Doctor through the mist , but he overpowers one and flees to the transmat ground station . The chase continues onto Skybase , where the Doctor finds his captive friends . He is about to release their handcuffs with his sonic screwdriver when the Marshal steps out , springing the trap . He blackmails the Doctor into cooperating . The Doctor outlines his plan to Jaeger : use the transmat ' s macrophaser to effect particle reversal in swaths across Solos . This will , of course , necessitate shutdown of the transmat system . Jo slips out of her cuffs and disarms the guard . Cotton tries to contact the investigator ' s ship , but guards are already at the door . Luckily , Stubbs holds them off . They are unwilling to fire on one of their own . The Marshal arrives and demonstrates no such hesitation . He sprays the room with blaster fire . Even as the investigator is contacted , Stubbs is gunned down . Leaving his fallen friend behind , Cotton leads Jo and Ky to an escape : the transmat . They enter the transmat , only to find it offline ; the Doctor ' s procedure has just begun . Sondergaard has returned to the cave . He is nearly accosted by a guard , only to be saved by a Mutt . Mutts have gathered . Sondergaard explains what he has learned . They have one chance : the Doctor . Far above , the Doctor and Jaeger begin sweeping their particle reversal beam across the planet . It undoes the damage of the rockets , but the Marshal is not satisfied . He threatens Jo if the Doctor does not terraform the planet further . Just then , the investigator ' s ship approaches Skybase . Jo , Cotton and Ky are kept as hostages to ensure the Doctor does not expose him to the investigator . Cotton realises that the Marshal has ordered them held in the thaesium storage chamber , a chamber that will be flooded with radioactivity as soon as the investigator ' s ship refuels . Outside Skybase , the ship slowly moves to dock . . . Episode 6 . The investigator arrives , immediately suspends all troops loyal to the Marhsal and begins his inquiry . With Jo in his grasp , the Marshal has an unwilling ally in the Doctor . The fuel probe from the docked ship enters the thaesium chamber . Jo , Ky and Cotton climb in , hoping to escape the radiation in the ship . They make their way to the inquiry . With Jo safe , the Doctor speaks freely . He accuses the Marshal of genocide . The Marshal erupts with rage , sputtering that the Mutts should be wiped off the face of the planet , which persuades the investigator . However , the investigator is obligated to due process and insists on proof of the Doctor ' s claims about the Solonian mutation . Sondergaard arrives on Skybase and tries to corroborate the Doctor ' s claim . He is followed by a Mutt , whose presence throws the proceedings into chaos . In the brouhaha , the Marshal grabs a blaster and guns down the terrified Mutt . The violence persuades the investigator to reinstate the Marshal ' s command . While the Doctor , Sondergaard and Jo flee , Cotton attends to Ky , who has been ill since their experience in the refuelling chamber . He pays for his compassion . The Marshal orders Cotton and Ky thrown back in the refuelling chamber , despite the thaesium radiation being at a lethal intensity . The Doctor seals himself in the lab . Sondergaard and he try to analyse the green stone . They put it under the particle reversal machine and realise it must be the catalyst that allows the thaesium radiation to bring the Solonians to their next stage . The Marshal blasts his way in . He orders Jo and Sondergaard thrown in the radiation chamber with Ky and Cotton . He does not know this is exactly what the Doctor wishes . With the combination of the stone , the radiation and Ky , the mutation should succeed this time . The Marshal keeps the Doctor in the lab to complete the terraforming . Sondergaard gives Ky the stone , and the Solonian begins to change into a Mutt , faster than any of the previous transformations . The Doctor continues to work under the watch of Jaeger and the Marshal but uses the distraction of the investigator bursting in to switch a pair of wires in the particle reversal device . The investigator has learned he is now the Marshal ' s prisoner . The Marshal intends to transform Solos into a " New Earth " and make the investigator ' s crew his first batch of settlers . The Doctor points out that he said the Marshal was quite mad . Ky ' s transformation completes . He emerges from the larval Mutt stage as a glowing , telepathic and almost omnipotent being . He thanks Sondergaard for his help and disappears , opening the door almost as an afterthought . The now godlike Ky floats through the corridors of Skybase . The guards he passes fall dead as he goes . In the lab , Jaeger throws the switch on the Doctor ' s device , only to be killed in the blast as his sabotage does its work . The Marshal trains his gun on the Doctor , but Ky appears and vaporises the Marshal in retribution for his torture of the Solonians . Ky thanks the Doctor and vanishes . With Sondergaard staying on to help the Mutts complete their transformation and Cotton appointed to oversee the withdrawal of the Skybase to Earth , the investigator wants the Doctor to return to " Hyperion " and give a full account of his involvement with the Solonian affairs . Aware that he is a complete , unqualified stranger masquerading as an official , the Doctor makes an excuse to leave by saying that Jo doesn ' t look so well , and Jo catches the hint . The Doctor and Jo head back to the TARDIS before the investigator can learn he ' s a phony . With a terrible pun , the Doctor returns to his blue box in the broom cupboard , breaking out the same way he broke into Skybase One — using the sonic screwdriver on the door controls . As the TARDIS departs , a familiar alert on the comm speaker brings their adventure full circle . " Attention ! Attention ! Computer confirms malfunction in storage area four . Investigate , please . Investigate , please . " References . " to be added " Home releases . DVD releases . The DVD release consists of 2 discs . It has been released on different dates : Region 2 : 31 January 2011 Region 4 : 3 February 2011 Region 1 : 8 February 2011 DVD Special Features include : Digital releases . This story is available : VHS releases . This story was released as " Doctor Who : The Mutants " . Released :