Colony in Space ( TV story ) Colony in Space was the fourth serial of season 8 of " Doctor Who " . It was narratively significant for being the first off - Earth story recorded in colour . It was the first time any companion had travelled in the TARDIS with the Doctor since " The War Games " and therefore , Jo Grant ' s first visit to another planet . It introduced the Interplanetary Mining Corporation ( IMC ) , which reappeared in several stories in other media . The story also introduced a new model of the sonic screwdriver unique to the Third Doctor . He had mentioned having one in " Doctor Who and the Silurians " , but this was the model ' s first physical appearance within a serial . Its debut here preluded the more frequent , conventional use of the sonic screwdriver as the Doctor ' s preferred gadget . The Virgin Missing Adventures novel " The Menagerie " retconned a link between " The Space Pirates " and " Colony " through the IMC . Subtextually , the script was Malcolm Hulke ' s intentional science fiction al comment on the struggle between European settlers and Native American s . " Colony " was the first " Doctor Who " director ial assignment for Michael Briant , who had been a production assistant , amongst other roles , during the Innes Lloyd and Peter Bryant producer ships . Briant later directed some of the most iconic serial s of the 1970s , including " The Robots of Death " and " The Sea Devils " . Synopsis . The Time Lord s discover that the Master has stolen their secret file on the Doomsday Weapon . They grant the Doctor a temporary reprieve from his exile on Earth to deal with the crisis . He and Jo arrive on the planet Uxarieus and become enmeshed in a struggle between an agrarian colony and a powerful mining corporation . Plot . Episode one . The Time Lord High Council discuss an issue with the Doomsday Weapon - something that only they and the Master know about . They decide to use the Doctor to help them with their problem and restore his freedom for the time it takes to help them . The Doctor is experimenting on a new dematerialisation circuit . Jo and the Brigadier try and convince him to stop . The Brigadier says that there is no sign of the Master but is called out when an agent thinks he has a trace in him . The Doctor is sceptical . Once the Brigadier leaves , the Doctor says he thinks he has fixed the dematerialisation circuit to allow him to bypass the homing control installed by the Time Lords . Jo is sceptical . For the first time , the Doctor shows Jo the inside of the TARDIS . When she says that it is bigger on the inside , the Doctor explains that it is dimensionally transcendental . All of a sudden the doors close and the TARDIS starts to dematerialise . The Doctor is confuse and says it is being operated by remote control by the Time Lords . The Brigadier enters the lab to see the TARDIS dematerialise . He orders the Doctor back . Jo thinks that the Doctor is playing a joke on her but he shows her the scanner to show they are outside the space - time continuum . Soon the planet Uxarieus rears into view . Jo wants to go back . A robot is trundling around a planet ' s surface . As it moves off the TARDIS rematerialises . Jo wants the Doctor to open the doors but he needs to check if the atmosphere is healthy . Once he has done that he opens the door . Seeing the alien landscape , Jo gets scared . She has always doubted the Doctor ' s stories of his travels through time and space . The Doctor says they should go for a quick look and then return . As they explore they are overlooked by a creature . They find track marks left by the robot and speculate that the planet must be inhabited . The Doctor wants to climb a hill to get a better vantage point . Jo is still scared but the Doctor convinced her to come . They find some dwellings atop all the hills . As they explore Jo turns to see a man pointing a rifle at them . An inhabitant of the planet , Martin , argues with the leader , Ash , about something he saw last night . Ash is sceptical but sends his right hand man David to explore . The Doctor is brought in by the man with the rifle , Leeson . He suspects them to be mineralogists who want to use their planet for mining . The Doctor reassures them that they are just explorers . Ash wants to see their papers and when the Doctor cannot produce them , Ash says they will spend the night here and not return to their ship . Jane , Leeson ' s wife , shows Jo to the dining hall . The Doctor examines their crop records . Lesson goes to attack him but the Doctor disarms him with Venusian Karate . The Doctor says it looks like they have had a particularly poor harvest for some time and that they are far below sustainable levels . Ash ' s interest is piqued . Outside , the creatures that observed the Doctor and Jo , steal the TARDIS . In the dining hall , the colonists squabble about the merits of Uxarieus in relation to Earth as Jo and Jane enter . Martin is the most vocal . He prefers Earth despite the fact that it was overpopulated and oppressive when they left . David enters and takes Martin with him to look for the creatures he saw . Mary , Ash ' s daughter , introduces herself to Jo . She reveals that it is 2471 and that they arrived a year ago . Leeson returns home and grumbles about the fact that there are no crops and that they shouldn ' t have come . Jane , his wife , said that on Earth they didn ' t have a room and now they have land . Lesson says that even Ash knows he ' s beaten . They here a noise outside and rush out . A huge lizard is outside . Jane radioes the main dome for help . She rushes for the rifle but is attacked . Ash and the Doctor are talking about the history of the colony . The Doctor questions Ash ' s decision to stay but also says that there is no reason why the crops aren ' t growing . Mary rushes in and tells of the attack . Ash and the Doctor rush off . Jo tries to persuade the Doctor not to go but he is convinced . Jo asks Jane if they checked for signs of life before they colonised . She says that when they arrived there were no creatures . By the time Ash and the Doctor arrive both Leeson and Jane are dead . One of the colonists report that they saw a lizard , twenty feet high , but as they approached it vanished into the darkness . The Doctor draws attention to some claw marks deep inside the dome and says that a creature that large could not have got so far into the building . The colonists are having a meeting and want to leave . Ash insists that they can ' t move on . They argue that there is no food . The Doctor agrees with Ash and says that the crops are being inhibited by an unnatural source that they can track down and destroy . This begins to change the mind of some of the colonists . They decide to stay and fight . Patrol guards bring in a stranger that they found collapsed outside . He says he is from a colony a long way from here and has been wandering for months . He says that all of his friends have been killed by giant lizards . The alien creatures that overlooked the Doctor and stole the TARDIS are examine things inside the Leeson ' s dome . As the Doctor and Ash enter they try and attack the Doctor but Ash calls them off . Ash explains that they don ' t speak but can understand what he wants . He says they are friendly now but we ' re quite hostile when they first arrived . Ash sends them away . The Doctor wants to examine the dome for evidence . Ash leaves him to find his own way back . As the Doctor starts collecting evidence he turns to see the giant robot entering the dome . Episode two . The robot is stopped by a uniformed man who asks the Doctor what has happened inside the dome . The Doctor explains the situation regarding the colonist . The uniformed man seems confused as he was under the impression that the planet was uninhabited . He says he is from the IMC and they have only just arrived . He says he needs to let Earth control know of the mistake . He asks the Doctor to come back with him to the ship . The Doctor refuses but the man says he has no choice . The Doctor tells the man about the death of the colonists . The man seems very concerned . They board the vehicle , programme the robot to go back to the ship of it ' s own accord and head off . The colonists talk to the survivor - Norton . He says that the primitives turned on them once the lizards destroyed their infrastructure . David tells Jo that their colony ' s history with the primitives haven ' t always been perfect . David thinks this will be the wake up call that Ash needs to move on . A primitive enters . Norton loses his mind and points a gun at the creature . Ash enters and stops Norton from shooting it . David days that the only reason why there is a truce between the colonists and the primitives is because they are giving food to them that they can ill afford to . Ash and David argue . Ash leaves and Jo tells David that Ash is right . On the way back to the ship , the Doctor notices that the TARDIS is gone . At the IMC ship , one of the workers , Morgan , presents Dent , the captain , a survey result that states that there is enough Durilinium on the planet for a million living units on Earth and questions why it was allowed for colonisation . They see the Doctor and the other IMC worker , called Caldwell , approach on their scanner . Dent tells Morgan to follow the same story they normally do ; pretend they don ' t know the planet is colonised and say it was all a mistake . The Doctor is shown into a room while Caldwell fetches Dent . The Doctor switches on an entertainment console which shows Earth news detailing war . Caldwell reports to Dent and tells of the death of the colonists . Morgan confesses that he had to kill them because they discovered him and started shooting . Caldwell says this isn ' t what he signed up for but Morgan says it is a means to an end . Dent shows Caldwell the report and the millions they will earn from the Durilinium . Dent goes to see the Doctor . The news is now reporting the overpopulation of the Earth . Dent enters and introduces himself and says it is a mistake that the colonists are here due to the hostile animal life . He suggests that the colonists leave as the IMC have mineral rights . The Doctor states that Earth needs new worlds to populate not minerals that destroy other worlds . Dent disagrees . The Doctor asks after his TARDIS . Dent says he will get someone to look for it and leaves the Doctor in the room while he sorts out someone to return him to the colony . On leaving the room , Morgan tells Dent that Caldwell is looking for the Doctor ' s TARDIS . Dent tells Morgan that the Doctor is not a colonist and that he may be from Earth ' s government checking up on them . Dent says that Morgan is to return him to the dome and kill him , making it look like he is another victim of the monster . Caldwell enters and says that there is no trace of the TARDIS . The Doctor is trying to find his way out of the room when Morgan enters . The Doctor asks why he was locked in and why he keeps being passed from person to person . Morgan says that he is to take the Doctor back to the colony and organise a meeting between Dent and the leader of the colonists . On the way Morgan asks if the Doctor can show him the dome where the colonists were killed . On the way to the dome they are stopped by primitives . Morgan tries to shoot them but the Doctor stops them . They attack and the Doctor uses one of their spears and Venusian Karate to disarm them , before getting in the vehicle and driving off . Mary and Jo make dinner . Jo asks Ash about the Doctor . He says if he isn ' t back by the time that David comes back from showing Norton around then he will send David out to get him . Jo says that Norton has made a very quick recovery . David shows Norton the power supply junction box manned by Jim Holden and a primitive . Here the power from the ship ' s nuclear generator is tapped and sent out around the colony . They return to the dining quarters and chat with Jo and Mary . Norton says that his colony was better equipped than theirs but it did them no good . Mary tells David that Ash wanted to see him . David heads off and Norton goes to lay down . Holden has fixed the power supply . Norton enters and strikes the primitive over the head with a spanner before attacking and killing Holden . Mary enters and tells Ash that dinner is ready . All of the power goes out . Norton enters and urgently fetches Ash . He takes Ash to the power supply junction box and shows him the scene . Norton says that the primitive killed Holden and then attacked him . He says that he killed the primitive in self defence . Ash sees that the relay circuits have been destroyed and that the colony will come to a standstill as they have no one to fix it . Dent says a message to IMC headquarters that there is tonnes of Durilinium and an issue with colonists . Caldwell enters and asks what is to be done with the colonists . Dent says that they will decide to leave . Caldwell realises what is going on and realises that the Doctor is in danger . He wants to go after them but Dent blocks him . Dent says that he can kill him there and then and say he struck him . Dent says that the death of the Doctor is a small price to pay for the Durilinium . Caldwell is unsure but Dent says that he knows the debt that Caldwell is in and that if he ruins his plan he will ensure he never works again . The Doctor and Morgan arrive at the dome . The Doctor shows Morgan the marks and says that he thinks it is a fake . Morgan shows the Doctor a robot that enters with huge claws on his arms . He says that it looks like the monster is going to claim another victim . Episode three . Morgan threatens the Doctor with his gun . The Doctor points out that any gunshot in his corpse will ruin Morgan ' s story . Morgan hesitates and the Doctor disarms him . Morgan escapes . The robot looms in on the Doctor who manages to reach the remote control and disable the robot . The colony is in chaos due to the limited power . Jo is worried about the Doctor . Ash initially says that he has more important things to worry about but then says he will send someone out to look for him . They hear the noise of an approaching spaceship . The IMC ship is landing next to the colony . Dent leaves to make contact with the colonists . Dent feigns surprise at the existence of the colony . Dent says he will send for an adjudicator to decide who the planet belongs to . Ash knows this will take years and will allow the IMC to mine the planet in the meantime . The Doctor enters and tells the colonists exactly what the IMC have been doing and that he looks forward to telling that to the adjudicator . Dent leaves . The Doctor says the creatures that have been plaguing the colonists was only optical trickery plus a robot with claws . Ash tells the Doctor about the power issues . The Doctor is more worried about the loss of his TARDIS but relents . Jo is concerned about the whereabouts of the TARDIS but the Doctor calms her down before he leaves . Norton stirs up dissent about the Doctor ' s story . Jo sticks up for him and says they could go and look through the IMC spaceship for proof . Dent is furious at Morgan for ruining their plan . Norton radioes Dent and warns him of David and Jo ' s plan . David and Jo sneak aboard the ship and avoid the robots and the IMC workers until they reach the Communication Deck . As soon as they enter they ambushed by Dent and his guards . The Doctor has fixed the power permanently . Ash says that Norton had been trying to fix the power with no success . The Doctor notes that it looks like someone has been trying to destroy the power source instead . Mary enters and says that Dent has sent for the Doctor . Dent tells the Doctor that Jo is under arrest for robbery . The Doctor asks what Dent wants and Dent says he wants the Doctor to remain silent when the adjudicator arrives . He refuses . The Doctor asks where Jo is . Dent explains she is placed by an explosive charge used for surveying . An IMC guard , Allen , attaches Jo and David to the explosive . David tries to break through but Allen advises him that that isn ' t a good idea . The Doctor tells Ash about the situation . Everything that Ash suggests puts Jo in more danger . David says that there is grease on the casing of the explosive . David uses some of the grease to ease Jo ' s hands from the manacles . David wants Jo to go to the dome to warn Ash but she insists on freeing David . She tries to break through the chains but it triggers an alarm on the bomb . This noise registers in the IMC ship . Dent checks with Allen . David is freed but as they go to escape he is shot and wounded by Allen who grabs Jo . Allen reports to Dent who sends guards after David . David evades some guards and heads towards the main dome but is discovered by two more guards who shoot at him . He runs but comes face to face with another guard . As the two original guards approach they hear a gun shot . The worker tells them that he sorted out their problem . As the guards leave , the worker is revealed to be Caldwell . He tells David that he can stop playing dead now . Caldwell helps David into his shelter where he frees him and checks him over and gives him an injection . David tells Caldwell of the situation with Jo . Caldwell advises David that the colonists should just leave as the IMC always win . Ash is organising a search for Jo when David enters . He tells them that they were being kept in the primitive ruins but Jo would have been moved by now . David ' s plan is to mount an attack on the IMC spaceship , get them to surrender , release Jo and make them leave . Ash argues and the Doctor says that it is a bad idea but David leaves to organise the colonists . The Doctor asks David for directions to where Caldwell is . The Doctor arrives at Caldwell ' s base . Caldwell says that Dent is just trying to scare the colonists . The Doctor warns Caldwell of the attack but says it can be stopped if Jo is freed . Caldwell agrees to help but warns that if the colonists attack it will not be a battle but a slaughter . Morgan is informed by radio that the adjudicator is nearby . He passes this news to Dent . Caldwell enters and orders that Jo is brought back or he stops surveying - something he will have to explain to head office . Dent relents but says that Caldwell has committed professional suicide . As Allen frees Jo , the primitives enter . Allen shoots one but is killed by a tomahawk . They kidnap Jo . The Doctor is dissuading Ash from attacking . Ash is unmoved . The Doctor tips Ash off about his suspicions regarding Norton and then says he has a better plan for gaining access to the ship . Mary is sent forward to engage the guards in conversation whilst the Doctor and David sneak up behind them . They knock them out . Dent tries to contact Allen but there is no response . Caldwell thinks it is a stalling tactic . The Doctor and David enter the ship in the uniform of the disarmed guards . Guards are soon alerted and an alarm is raised . They take an IMC worker hostage and demand they are taken to the control room . As soon as they enter the Doctor demands to know where Jo is . Dent says she has vanished . The Doctor leaves David in charge so he can go and look for her . Dent warns David that he is committing an act of piracy . David orders Dent to surrender . The Doctor and Ash go to the primitive ruins and discover Allen dead at the hands of the primitives . The Doctor says they must be turning against humanity . Ash suggests they have taken Jo to their city but warns the Doctor that no one has ever gone to the primitive ' s city and survived . Episode four . Jo is led to a rock that opens in front of her . She is led in . The Doctor says he is to go after Jo . Ash dissuades him and says that they have been known to ransom humans for food . The Doctor says he will go and make that offer to them . As he leaves the hear the noise of a ship . The adjudicator has landed . Dent says that the adjudicator will not look kindly on the colonists actions of seizing the ship . David finds the projector that displayed the lizard alongside the claw that made the scratches . He says he will use this as evidence . Ash rushes to talk to the adjudicator by radio . He is brusque and says he wants to meet both parties at the same time . Ash is worried that they know look like the aggressors . Jo is summoned to the leader of the Primitives . He is smaller than the rest , white and horrific looking . She screams . Ash contacts David to tell him of the adjudicator ' s demands . David agrees to free the IMC workers . Alec Leeson - the brother of the killed colonists - wants to kill the IMC workers . Morgan turns on Dent and says it was all his fault and he has proof in a secret compartment under the desk . David asks to show him but it is a trick and Morgan grabs a gun and holds them up . The Doctor finds the entrance to the Primitive City and finds he is surrounded by Primitives . He offers them food in exchange for Jo . He is led in . The adjudicator meets with Ash and Mary . As he enters the dome , Ash panics as to the whereabouts of David and the IMC workers . As the adjudicator turns , he is revealed to be the Master . Jo is pleased to see the Doctor . She tells him of the leader of the Primitives and the Doctor speculates as to whether they are two races . The Doctor tells Jo of the plan to free her . Jo says that the Primitives are descendants of a highly advanced civilisation and shows him a visual history painted on the walls that shows buildings , cities , machines and flight . However as the history continues it shows ruin and death caused by some kind of catastrophe . The last slide sees a man forced through some kind of hatch in a form of human sacrifice . The costume enters and walks up closely to the two humans . The Doctor speculates that it is almost blind . The Doctor makes the offer of food . The creature consults the pain where the sacrifice is shown , points to it and then points to the Doctor before they all leave . Ash presents the facts to the Master . The Master asks if there is any evidence but David has to admit that it has been destroyed . Ash does not tell the Master about the killings . The Master calls the IMC to make their claim . A primitive enters . The Doctor distracts him with a magic trick before knocking him out . They escape and sneak past the leader they saw before . They discover there is a number of these white half - blind Primitives operating alongside the taller green ones . The white Primitives find the primitive unconscious and send the guards after the Doctor and Jo . They are soon surrounded by a mixture of white and green Primitives and led into a central room . One of the white Primitives opens a hatch which leads to a blinding light . The Doctor suggests it is some kind of reactor . A panel opens in the wall and a tiny version of the white Primitives emerges from behind sat on a throne . It tells the Doctor and Jo that all intruders are forbidden here under punishment of death . The Doctor says that if they are a civilised society they should not kill . The creature states it is their law but the Doctor says that with law must come justice . The creature senses that the Doctor is a being of superior intelligence so says that he will let him and his friend go but warns him that if he returns he will be destroyed . As the Doctor and Jo leave , the creature returns back into the wall . The Doctor and Jo leave the city . The Doctor speculates whether they are dealing with three races or three mutations of the same race . Jo says they do not have time for philosophy and need to return to the main dome . The Master has heard the IMC ' s statement and is weighing up his findings . He explains that an error occurred due to a faulty computer which allocated both parties the planet so he has to judge each case on its merits . The Doctor and Jo enter . All parties recognise each other . The Master says he needs time to consider his decision and withdraws , followed by the Doctor and Jo . The Doctor asks why he is impersonating the adjudicator - the Master dodges the question . The Doctor threatens to expose him as an imposter but the Master says his documents are forged so perfectly nobody would believe him . The Master questions if the Doctor has any credentials . When the Doctor admits he doesn ' t the Master says he could send him back to Earth as a prisoner unless he keeps quiet . The Master returns and sums up the case in favour of the IMC . He says the colonists are failing but the IMC can contribute to the issues on Earth . Later the IMC workers are getting drunk to celebrate . Caldwell asks what happens if the colonists refuse to leave . Dent says they will be rebels and that Morgan knows how to deal with rebels . Ash suggests they appeal but David says that is a lengthily process by which time the planet will be decimated . David wants to capture and disarm the IMC workers and force them to leave . Ash says this will make them outlaws but David says they could form a republic independent of Earth . Ash forbids and says he wants to carry out his protest by legal methods . David says he has no intention of changing his mind . Ash goes to the Doctor and tells him of David ' s intentions before he goes off to talk to the Master . Jo asks why the Doctor doesn ' t tell Ash that the Master is not the real adjudicator . The Doctor explains that he wants to figure out why the Master is here first . He follows Ash to listen to his conversation with the Master . The IMC ship receives a message from the adjudicator but the reception is poor . The message is that all parties must meet to ratify the decision . The message is really from David who is planning an ambush . The Doctor eavesdrops on Ash and the Master ' s conversation . The Master says the appeal will fail unless of special circumstances like a discovery that the site has significant historical interests . Ash Mentions the ruins of the Primitives . The Master asks for more information . The colonists spread out and discover that Norton is missing . Alec goes to look for him . Norton tries to contact the IMC workers but is interrupted by Alec . He sees the radio and the two fight . Alex is shot but the radio is destroyed . Norton returns to the colonists and takes his positions . As the IMC workers enter , Norton screams out that it is a trap . David kills Norton and a fire fight ensues with deaths on both sides . The Doctor runs forward with every intention of stopping the fight but the Master stops him . He pulls out a gun and tells the Doctor and Jo that they are about to fall victim to stray bullets from the gun fight . Episode five . Ash interrupts the Master and implores him to stop the fight . David captures Dent and forces the surrender of the IMC workers who are to be kept under guard . Ash rails against David for his actions . David says he wants the Master to be accompanied back to his ship to go back to Earth . The Master says that they need him to adjudicate with Earth . He goes on to explain how impressed he is with the colonists and their plea that the planet has historical interest . He wishes to see the Primitive city . The Doctor tells Ash that he is not the real adjudicator . The Master says that they can check his credentials with Earth and then asks for the Doctor ' s credentials before he excuses himself with Ash saying they shouldn ' t trust the Doctor with their secrets . The Doctor tells Jo that they need evidence on the Master and says they should go and look in his TARDIS . The Doctor says that he still has the key that he stole when the Master first came to Earth . David takes the IMC workers back to their ship and orders them to leave the planet and that the adjudicator is now on their side . When left alone Dent orders the adjudicator ' s details should be checked with Earth . David recontacts the ship and says they have placed explosives under the ship that will go off if they do not leave immediately . Morgan thinks that they are bluffing but Dent is spooked . The Doctor and Jo enter the Master ' s TARDIS - first circumnavigating an alarm beam . The IMC ship hovers over Uxarieus . They receive a message from Earth with a picture of the real adjudicator . Dent orders they go back into landing orbit . The Doctor finds a mineralogical survey of Uxuarieus and a range of other planets ; the Master must be looking for something . Jo also finds the real adjudicator ' s credentials . The Doctor wants to find out why the Master is so bothered with this planet . The Master checks a device that shows footage inside his TARDIS and sees the Doctor and Jo snooping around . He is interrupted by Ash . He hides the device but presses a button on it . A gas is released in the TARDIS and the door is closed . Both the Doctor and Jo drop to the ground . Ash shows the Master the chartered areas around the Primitive city but says that the Doctor is the first person to go there and return . The Master says he will go and get the Doctor . The IMC ship lands on the other side of a range of hills . They intend to go and and surprise the colonists . Caldwell is unsure . The Master wakes the Doctor and says that he needs him as a guide . He intends on using Jo as a hostage . David is concerned that he can find neither the Master nor the Doctor . David implores Ash to hand the IMC ' s guns around to the colonists but Ash says that there is no need . David disagrees . The guards around the main dome are disarmed by IMC guards and the main dome is infiltrated . They storm Ash ' s room and take him hostage . They take their guns back . David finds the guards unconscious and a fire fight ensues . Ash is led into the fracas as a hostage of the IMC . The colonists surrender . They are imprisoned and Dent says that Ash and David need to be kept safe in preparation for trial . The Master has stored the Doctor and Jo in cubicles overnight . He frees the Doctor and shows him a device where he can release lethal gas into Jo ' s cubicle remotely . As he leads the Doctor out , the Doctor drops the key on the ground . Dent opens the trial of Ash and David . They are being tried for destroying property and equipment belonging to the Interplanetary Mining Corporation , assault and murder of IMC personnel , trespass on a planet lawfully allocated to IMC , and armed rebellion against the lawful representatives of the Earth ' s government . David is furious and says that he wished he had killed the IMC workers when he had the chance . Ash asks why the adjudicator is not present . Dent says he doesn ' t need the adjudicator as he is now the legal ruler of Uxarieus . He states that three of the crimes they have committed are punishable by life imprisonment and the other two by death . He passes judgement that their executions are to be suspended on the proviso that they leave the planet immediately . Ash says that the ship will not survive takeoff but Dent is unmoved . The Primitives see the Master and the Doctor approaching the city by car . They are stopped by an irrigation pipe in the road . As the Doctor goes to move it the Primitives cause an avalanche which knocks the car over . The Doctor warns the Master that he is to be attacked by a Primitive . The Master kills it . They continue their approach to the city on foot . Mary radioes Dent ' s orders to the rest of the colonists . Caldwell says that the ship is not in the best condition . Mary begs Caldwell to show mercy . Morgan can ' t find the Master and that the hatches on his ship are sealed . Dent tells Morgan to take Caldwell to the ship and use explosives if needs be . Caldwell tells Dent that the colonists ' ship could explode on the ground . Dent orders all IMC workers inside on blastoff . The Doctor leads the Master to the entrance but doesn ' t know how to get in . The Master threatens him . Caldwell and Morgan give up and are about to blow the door off when they find the key . They go in and find Jo but they have triggered the alarm . The Master sees what has happened and goes to press the button . Episode six . The Doctor uses Venusian Karate to disarm the Master but their altercation is broken up by the Primitives who lead them into the city . Morgan and Caldwell manage to free Jo who tells them of the Master ' s plans and where he has gone . The Doctor and the Master are led to where the Doctor was held previously . The Master offers to help the Primitives but they leave without heeding him . The Doctor shows the Master the pictorial history . Jo has explained to Caldwell the history of the Master but Dent interrupts and says that Jo is to join the colonists on their ship . Caldwell seems to enforce the message but hides Jo under tarpaulin in a buggy . The Master is impressed with the pictorial history . He explains that this planet used to be the centre of a great civilisation of a super race of which the small white creatures used to be a ruling race . This super race developed a Doomsday weapon but ended up becoming priests that worshipped technology and couldn ' t bear to be destroyed by it . The Doctor explains that they are to be sacrificed to this technology unless they do something . The Master says he wants to use this weapon to hold the galaxy to ransom . As the Primitives enter , the Master shows the Doctor a gas mask and canister . As soon as the Primitives enter , he deploys it and he and the Doctor escape . Morgan checks the list of names aboard the colonists ' ship and questions why David ' s name is checked off . Mary insists he is aboard . Ash says he is ready to go . He tries one last time to convinced Dent . He says he is the only qualified pilot and asks what Dent would do if he refused to leave . Dent says that he would guard the door and kill anyone that left the ship . As Ash heads off Dent orders a guard to keep , watch of the ship at all times . The Doctor and the Master are looking for the Doomsday Weapon . The Master thinks they are nearly there . Morgan sees Ash and Mary aboard the ship . Dent is turning the colonist base into an IMC base . Unbeknownst to him , David is watching over him . A security guard watches the ship . Dent checks on the guard by radio . David sneaks up and knocks the guard out after a prolonged fight . Dent and Morgan are restless as to why the ship hasn ' t taken off . They get the colonists ' ship on video link . Ash explains their is an electrical fault regarding their life support . He says it will soon be fixed and that the countdown will begin in a few moments . Caldwell and Jo come across the Doctor and the Master ' s upturned buggy . They watch as the Colonist ' ship takes off and explodes . Caldwell is emotional . The Master and the Doctor have arrived at the heart of the Doomsday Weapon - a weapon that stretches miles around them . The Master says that the weapon has the capacity to blow up the Sun - in fact its prototype created the Crab Nebula . Caldwell and Jo arrive at the entrance to the Primitive City but can ' t get in . They are at the point of giving up when the door opens . A Primitive exits as Caldwell hides . As it approaches Jo , Caldwell jumps out and knocks him over . He holds the door opens and the two go in . The Master says that the Doctor could come in with him , saying that the Doctor could reign benevolently and end war , suffering and disease . The Doctor turns him down and says that absolute power is evil . The Master tempts him again and says that he is offering a half share in the universe . Caldwell and Jo are looking for the Doctor and the Master but Jo has to admit she is lost . Dent wants to know the whereabouts of Caldwell and says that Morgan should go and look for him . Morgan is worried about the trouble from Earth after the death of the colonists . Dent says he has fabricated a document saying that the colonists refused help with their ship . The Master begs the Doctor to see reason but he refuses . The Master tries to turn him against the Time Lords but the Doctor says he would rather see the universe rather than rule it . The Master is infuriated and goes to kill him but the leader of the Primitives emerges from the wall and demands to know why the Doctor has returned . The Master says he has come to offer a plan that will restore the city and planet to its former glory . The Doctor begs the leader not to listen . The Master says that the planet oils be the centre of a mighty empire . The Doctor asks if the weapon has ever brought any good to the planet . The leader says that it was the radiation from the weapon that polluted the soil of their planet and led to their downfall . The Doctor says that that is why the weapon should be destroyed . The Master begs the leader and says they could be gods . The leader says the Master shouldn ' t be a god . The Master tries to kill the leader but he uses his telekinesis to remove the weapon from his hands . The leader tells the Doctor that there is a self destruction mechanism on the weapon and asks the Doctor to activate it . The Doctor operates the lever with the help of the leader . The leader tells the Doctor to leave at once or he will be destroyed with the city . The Doctor runs while the city starts to crumble . As he leaves the Doctor finds Jo and Caldwell . As they head off they find the Master and ask for his map to help them leave . He refuses but Caldwell pulls his gun and forces him . They leave just as the city explodes . As soon as they leave the Master tries to disarm Caldwell but fails . Soon all four of them are surrounded by IMC workers . Morgan orders Caldwell away from the other three . The Master tries to take control of the situation but is rejected by Morgan as an imposter . The Master then sides with the Doctor . Morgan goes to kill them but Caldwell tells him to stop . Morgan turns to him and says that he is lucky to not be dying too . This momentary distraction allows a group of colonists to surprise the IMC workers . As a fire fight ensues , the Master steals a buggy and flees . David forces the surviving IMC workers to surrender . Jo realises that the Master has left . They take a buggy and pursue him . The Master arrives in his TARDIS and sees the Doctor and Jo pursue him on the scanner . As the Doctor and Jo arrive they see the Master ' s TARDIS dematerialise . Later , the Doctor explains to David that now the weapon is gone the crops will grow . Jo asks how the colonists survive . David explains that , once the guard was knocked out , the rest of the colonists left apart from Ash who sacrificed himself to create a decoy to lull the IMC workers into a false sense of security . The colonists interrupt to say they have found the Doctor ' s TARDIS in one of the Primitive dwellings . Caldwell is now working with the colonists and tells them that a real adjudicator is on his way . As they talk the TARDIS dematerialises behind them . The TARDIS returns on Earth the exact moment it left . The Brigadier sarcastically congratulates the Doctor on his short trip . Jo tries to explain but the Doctor says there is no point as the Brigadier wouldn ' t understand . Home video and audio releases . DVD release . The commentary was recorded in January 2011 , and the DVD was released on the 24th of October , 2011 . Digital releases . This story is available : VHS releases . This story was released as " Doctor Who : Colony in Space . " Released :