The Defectors ( audio story ) Publisher ' s summary . Jo Grant is shocked to find most of her colleagues are missing . Then she discovers that the Doctor has inexplicably changed . But there ' s little time to worry about it all , as she and her misplaced Time Lord friend are whisked to the mysterious Delphin Isle on a matter of national security . There , they encounter a disturbingly odd form of local hospitality and learn of a highly classified incident that took place during the Cold War . Why exactly have they been brought here ? And what is the truth concerning the bodies in the harbour and the vast project being undertaken under a cloak of secrecy ? Plot . Part one . Jo Grant watches from a window at UNIT HQ as a helicopter lands . Thinking it might be the Brigadier , she calls out to the Doctor , who is in his laboratory . Upon hearing odd sounds from the TARDIS , she assumes that he is busy working on it . Jo notices a lot of soldier s coming out of the helicopter . As she still can ' t get any response from the Doctor , she decides to go talk to Mike Yates , who is standing in for the Brigadier , while he is in Geneva . However , upon reaching his office , Jo is surprised to find Mike gone , and a Captain Cornelius in his place . Cornelius explains that Mike has been relieved of duty , and is now at a top level security briefing in London . All UNIT personnel have been evacuated from UNIT HQ and Cornelius has orders to take the Doctor and Jo to a secure location . As Jo proclaims that there ' s no way that they ' ll convince the Doctor to go along with it , she opens the door to leave the room , only to find a stranger outside the room . The man greets Jo , stating that he is not quite the Doctor she was expecting . Meanwhile , at an unknown location , Shedgerton is standing in some sort of daze , mumbling to himself . A group of soldiers approach him , led by Commander Wingford , who convinces the dazed and confused Shedgerton to return to the base with him , for a matter of national security . Back at UNIT HQ , Jo questions the Doctor on what is going on . But , he is just as confused as she is , having no idea what has just happened . Jo suspects that it might be another incident , like the one where she met the First and Second Doctors , but now she ' s meeting a fourth Doctor . The Doctor reveals he is the seventh incarnation , and that none of his other selves are here . He has no idea what is going on , not even if it ' s interference from the Time Lord s . Jo is suspicious now , questioning whether this strange man in front of her really is the Doctor . Cornelius joins the conversation , somehow recognising the Seventh Doctor . He tells the Doctor that he and Jo will be moved to a secure location . The Doctor asks Jo what is going on , but she has no idea . When the Doctor tries to object to being taken away , Cornelius ' soldiers aim their guns at the duo , leaving them with no choice but to go along to the helicopter . As the two are taken away to the helicopter , Cornelius goes and confirms the location of the TARDIS . The Doctor is curious what took Cornelius so long to join them in the helicopter , but he gets no answers . As the helicopter lifts off , Jo notices a lorry arriving at UNIT HQ . Upon question Cornelius , he decides it ' s time for hoods to be put on the two , so they can ' t see anything further . Meanwhile , Shedgerton , still confused and dazed , is in his room at the base , when he is visited by Wingford . Wingford recommends for Shedgerton to go to Level Zero - One . Back in the helicopter , three - and - a - half hours later , the Doctor wakes up Jo , who fell asleep . He predicts that they ' re about to land . His prediction is proven correct , as the helicopter lands a minute later . Jo is still suspicious of the Doctor , as he hasn ' t explained anything about his presence , but the Doctor has no explanation to give . The hoods are removed from their heads , revealing that they are now on an island , somewhere . Cornelius leads them to a village on the island , where the two will spend the night at the pub called The Delphin Arms , before coming to the base the following morning . The Doctor finds this all suspicious , since he and Jo were urgently required to come to the island , but now their time is being wasted at a pub . Cornelius just states he ' s following Commander Wingford ' s orders . Inside the pub , the Doctor reveals that he noticed that Cornelius was wearing makeup . The pub ' s owners , Claire and Jeremiah , welcome the two , having been expecting them . They reveal that the island is Delphin Isle , before getting the two some beer . Meanwhile , Cornelius is contacted by Wingford , who wants to know if the Doctor and Jo are happy . Cornelius reveals that the Doctor is suspicious of them , but Wingford is convinced that they ' ll be happier by tomorrow . Cornelius asks Wingford about what is going on in London , and Wingford reveals that all security protocols are still active and that they shouldn ' t have any trouble before they are ready . Wingford then asks for Cornelius to keep an eye on the pub . Back in the pub , the Doctor and Jo find that the beer tastes horrible , and that the food is nothing more than canned food , that hasn ' t been heated properly . They pretend to enjoy it to keep the pub owners at ease . After the meal , the two are taken upstairs to their bedroom s by Claire , who surprises them by referring to them by name , even though she didn ' t know their names earlier . The Doctor goes into his room , but Jo lingers outside for a little longer , having noticed that the bar has gone silent . Once inside her room , she pulls out a transceiver that she had concealed , and contacts Mike . Meanwhile , Cornelius reports in to Wingford , who is monitoring the conversation between Jo and Mike . Mike has no idea what ' s going on , as he ' s been unable to get any answers , nor has he been able to contact the Brigadier . Before Jo can tell Mike much of anything , Wingford jams the signal . He ' s not worried , as he ' s sure the Doctor and Jo will adjust to being there . Back in her room , Jo tries and fails to reestablish contact with Mike . The Doctor walks in , revealing that they were talking loud enough for him to hear from his room . Jo decides to question the Doctor on his identity and tests him . He answers all her questions correctly , but she is still not fully convinced . The Doctor and Jo leave the room to go investigate a few places . Their investigation of the pub reveals that the food was indeed canned food , and that the beer was years old and would ' ve probably killed them if they had drank the full pint they had been given . The two head to the harbour , to investigate the boat s there . They sneak past the soldier standing guard outside the pub , but they notice he is acting oddly , just staring at nothing . Upon reaching the boats , they find something in the water . Looking closely , they realise that there are bodies in the water , the bodies of the people who were in the pub , all of them dead . Part two . The Doctor and Jo quickly rush to pull the body of Jeremiah out of the water . The Doctor checks his pulse and confirms he is dead . The Doctor also notices an odd detail . The bodies of the people are blue , too blue than what would be expected of drowned bodies . The soldier from the pub arrives and pulls his gun on the duo , somehow not seeing the dead bodies . Cornelius arrives and takes charge of the situation . When the Doctor and Jo point out the dead bodies , Cornelius notices them , and is horrified . He quickly orders the soldier to go get some help . Cornelius proclaims that he ' ll inform the local police officer , who will then get help from the mainland . When asked by Jo exactly where the help will come from , he refuses to answer , proclaiming it to be top secret . He assures them that a full investigation will occur , but help won ' t be able to arrive on the island until Thursday , which is five days from now . He promises to see if they can get help to arrive sooner than that . The soldier from before returns with other soldiers . Cornelius orders them to get the bodies out of the water and to a hospital , where they might be saved . Jo is perplexed by that , as the people in the water are likely beyond saving at this point . The Doctor is curious how the locals are able to cope with all of this , but Cornelius tells him that they all agreed to this . The people and the village are here as camouflage for the base . The Doctor notices that no one has come out of any of the houses to see what is going on , but Cornelius states that the villagers know not to ask questions . Cornelius decides it ' s time for the Doctor and Jo to go to the base . As the two are being taken away , the Doctor notices one more thing , now that the sun has come up . The boats are old , rotten , and falling apart , which means no one has been using them for a long time . Meanwhile , a soldier at the base knocks on the door of Shedgerton ' s room , who ' s locked himself in , refusing to go to Level Zero - One . The soldier leaves to go get a passkey to get into the room . Shedgerton continues the mumble to himself . In his office , Wingford receives a call from an unknown individual . Wingford assures his caller that a vital component will soon arrive from the mainland . He also assures the caller that the security protocols that he had activated are still active and unquestioned , and that the Doctor and Jo are being brought to the base right now . He is then instructed to have all nonessential personnel wear security masks . He admits that the Doctor and Jo are becoming suspicious , but there ' s nothing the two could do now to ruin things . The Doctor and Jo are brought to a pool of water and get on a boat . The boat is rowed to a specific area of the pool . Cornelius contacts the base and tells them to activate it . The water suddenly starts lowering , revealing the pool to be a secret water elevator . The soldier returns to Shedgerton ' s room and opens the door , only to find that Shedgerton has disappeared . He contacts Level Zero - One and confirms that Shedgerton didn ' t go there . The Doctor and Jo are brought into the base , and Cornelius leads them towards Wingford ' s office . Watching them from the shadows is Shedgerton , who mumbles to himself about how the Doctor and Jo are new people who haven ' t defected yet . The Doctor notices the workers wearing anti - radiation gear . Cornelius tells them it ' s to protect them from radiation , but doesn ' t say what kind or where it ' s coming from . Back in his office , Wingford receives another call . It ' s the soldier , telling him that Shedgerton has disappeared . Wingford orders he soldier to find him and make sure he goes to Level Zero - One . A knock on the door forces him to hang up . Cornelius enters the room with the Doctor and Jo . Wingford welcomes the two to the base . He offers to have some tea made , but the duo jokingly respond that would rather have sour beer and lukewarm canned food , which confuses Wingford . He expresses his sympathies for what they experienced at the harbour , with discovering the dead bodies . The Doctor asks him if anything like this has happened before . Wingford assures him that nothing of the sort has ever happened . Jo asks if the police have been informed about the bodies , to which Cornelius says that they have . Jo then asks when he informed them , as he was with the two of them the entire time . Cornelius quickly states that he told his sergeant to take care of it . Jo invokes her security clearance as a member of UNIT and asks that she and the Doctor be told what ' s going on in the base . Wingford surprisingly agrees . He arranges for Jo to be taken on a tour of the facility , while the Doctor is to remain with him , as he has much to discuss with him . The Doctor states he wants to also go on the tour , but Wingford wants the Doctor to look over some things in the office , before joining Jo on the tour . Jo would rather have the Doctor come along with her , but Cornelius tells her that the Brigadier is anxious to see her . The duo are surprised to hear that the Brigadier is on the island , when he should be in Geneva . According to Wingford and Cornelius , he arrived shortly before they did . The Doctor asks to speak with the Brigadier . Wingford agrees and Cornelius calls Level Zero - One , asking a worker there to put the Brigadier on the line . Cornelius apologises for the static , as the signal in the base isn ' t good in the lower levels . The Doctor talks to the Brigadier , who apparently recognises the voice of the Seventh Doctor , but the signal cuts out . The Doctor suggests that Jo stay here with him , but Cornelius is against it , as there is a tight schedule to follow . Jo questions that , as their time was wasted by going to the pub . Wingford promises that the duo will get their answers and insists that Jo go with Cornelius to see the Brigadier , while the Doctor remains with him . The Doctor finally agrees , stating that he doesn ' t believe they have a choice . The Doctor asks Jo to pass a message to the Brigadier , apparently a joke between the two of them . Wingford is confused at the idea of a joke for a moment , but then proclaims that the joke was amusing . He then begins to tell the Doctor about the base . As they walk along , Jo asks Cornelius how long he ' s been working on the island . Cornelius tells her he ' s been working there for a long time , and that ' s all he ' ll tell her . However , he has now been authorised to tell her about the base . The base was established back during the Cold War , as a top secret debriefing safe haven for high ranking defectors , the kind of high ranking defectors they wanted the Soviet Union to think had vanished or died . An island no one knew existed was the perfect place to hide them . Cornelius leads Jo to an elevator , which they take down to Level Zero - One . Back in Wingford ' s office , he continues to tell the Doctor about the base . Back in 1951 , an experimental Soviet craft crash landed in the sea , just off the island . They recovered the craft and pilot , who was a defector . According to Wingford , that defector is still alive and on the island . He is helping Wingford and the others to repair his craft , which the Doctor finds odd , considering that 1951 was years ago . The pilot is old now , and on life support down at Level Zero . According to the medics , he doesn ' t have long to live . The Doctor realises he was brought here to help repair the craft . The Doctor wonders why all this secrecy was used , instead of them asking him directly . Wingford says that he wanted the Doctor to be comfortable . The Doctor calls that into question , bringing up the poisonous beer and the horrible food at the pub . A pub whose owners along with all of their customers end up dead in the harbour . Wingford is confused about the beer and food , and states that what happened to the people was most regrettable . The Doctor asks him whether he believes it was mass suicide or mass murder , but Wingford doesn ' t have an opinion on the matter , and is strangely focused only on the task at hand . The Doctor asks him how experimental the crashed Soviet craft is . Wingford tells him that its drive mechanisms are unique on this planet . Jo and Cornelius arrive at Level Zero - One . Cornelius guides Jo to an airtight door , to which he tells her will lead to the room that the Brigadier is in . Jo can hear his voice through the wall , and goes into the room , only to find it ' s an empty chamber . Cornelius suddenly closes the door behind her and locks it , trapping her inside . As she bangs on the door , demanding to be let out , a sticky , blue liquid starts pouring into the room . Wingford shows the Doctor the drawings they made of the craft ' s drive systems . The Doctor notices how highly advanced those systems are . At that time , another call comes in for Wingford . It ' s Cornelius , reporting that Jo is with the Brigadier now . Back in the chamber , Jo fights to stay above the liquid filling the room . A hatch on the ceiling suddenly opens , revealing Shedgerton , who pulls Jo to safety in an air duct . They watch as the chamber fills the rest of the way . Jo wonders what ' s going on and where the Brigadier is . Shedgerton reveals that the Brigadier was never here . Jo and the Doctor were being tricked by recordings . Shedgerton examines Jo and determines that none of the liquid got into her body . Jo notices that Shedgerton ' s skin is completely blue . Shedgerton points out that the blueness is beginning to fade , but that it will take a while to completely fade away . Jo wants to know why Cornelius locked her in that chamber . Shedgerton proclaims that everyone is a defector , everyone on the island and in the base . However , the blue liquid has been losing effect as time has gone by , to the point in which Shedgerton ' s mind began to reassert itself , enough for him to avoid one of his scheduled submersions in the liquid . Upon avoiding that submersion , he found his memories and identity beginning to come back to him . However , his body hasn ' t fully purged the effects of the liquid yet , so he is still getting bouts of confusion . When he saw Jo and the Doctor arrive , he knew he had to stop them from being turned into defectors . Shedgerton decides to show Jo everything that ' s going on . Back in Wingford ' s office , the Doctor has studied the drawings and has noticed that the drawings aren ' t quite drawings at all , and that the paper is a very odd material . He ' s also noticed that the craft is more advanced than any sort of jet airplane . Back in the ducts , Shedgerton leads Jo to a panel . With her help , he is able to remove it . He gestures for her to look down into the room below . She can see the workers in there , no longer wearing the anti - radiation equipment . They were wearing it before to hide their blue skin . To Jo ' s shock she recognises two of the workers as Claire and Jeremiah , but that ' s impossible , as she knows the two are dead . Part three . Shedgerton pulls Jo back , making sure they aren ' t seen by the passing workers . Once they ' re gone , he puts the panel back in place . He reveals to Jo that the people in the water weren ' t dead , only sleeping . Jo finds that hard to believe , as the people in the water weren ' t breathing , and their skin was blue . Shedgerton points out that everyone on the island has blue skin . Jo remembers the Doctor ' s observation of the makeup on Cornelius and realises that he and Wingford are both wearing makeup to hide their blue skin . She then asks what the point of the blue liquid is . Shedgerton tells her it ' s to make everyone compliant . Jo asks where the blue liquid comes from . Shedgerton is afraid of the liquid and remarks how nothing has been the same since " they " arrived . He remembers that it was a bright , sunny day , a long time ago . A blue craft was pulled ashore from the water , where it had crashed . Jo asks if it was a Russian plane , but Shedgerton remarks that it wasn ' t a plane at all . Before he can comment further , an alarm goes off . Jo is afraid that it means that they have been found . In Wingford ' s office , the Doctor hears the alarm and asks about it . Wingford tells him it ' s just the alarm for a shift change in the lower levels . The Doctor looks back at the drawings and compliments the drive system , revealing that he understands how it works , as he ' s figured out that Wingford wants to reactivate it . The Doctor states that he ' ll need to see the documentation of all the work done so far . He goes over to the file cabinet , the likely place for the documents . He goes through the files and finds a photograph from 1951 , featuring Wingford , and he looks exactly the same then as he does now . He finds another photo with Cornelius , Claire , and Jeremiah , and they also looks exactly the same today , as they did in 1951 . Wingford tells him the documents are in the next drawer down and the Doctor goes there . Back in the duct , Jo asks why they haven ' t be captured yet . Shedgerton realises the alarm wasn ' t for them , but for the workers . They watch as the workers go to the chamber and enter , allowing themselves to be submerged in the blue liquid . Jo asks Shedgerton where the liquid comes from . He remembers that there is a pipeline , so all they have to do is follow it to its source . The two climb out of the duct and start looking for the pipeline . Back in Wingford ' s office , the Doctor sees that the workers have successfully reconstructed the drive system . All that ' s left is for the power couplings to be aligned and the energy from the fuel stacks needs to be initialised . The Doctor offers to make the calculations for the coupling alignment , but warns that it will take a while . Wingford asks him to start immediately . There is a knock on the door . It ' s Cornelius , who ' s nervous because Jo is missing . The Doctor proclaims that she has most likely sneaked off somewhere with the Brigadier to have tea . He asks if his joke was passed on to the Brigadier . Cornelius tells him that he did , and that the Brigadier found it most amusing . Cornelius asks to have a word in private with Wingford , so the two walk off , leaving the Doctor to ponder over Jo ' s escape , expressing pride at her for doing so . Jo and Shedgerton locate the pipeline , and realise that it leads downward , to Level Zero . Shedgerton can ' t remember what ' s on Level Zero , but knows that it ' s something terrible . Jo proclaims that they need to find out what ' s on that level . Wingford is convinced there is a connection between the disappearance of Jo and the disappearance of Shedgerton . He has found out that Shedgerton found a way to avoid the submersions . He was free when the Doctor and Jo entered the base . Cornelius isn ' t worried , as there ' s nothing they can do to disrupt them . But , he thinks they should waste no more time with the Doctor and have him submerged . Wingford is against it , as he believes they need the Doctor ' s mind intact . Cornelius objects , believing the Doctor is a danger to them . He obviously knows more than he lets on . Wingford is willing to take the risk of not having the Doctor submerged , as they need him to make the alignment calculations . Suddenly , the Doctor enters the room . Apparently , he heard raised voices and came to see if he could help . Wingford asks him if he has finished his calculations . When the Doctor says he hasn ' t , Cornelius claims that he is procrastinating , and trying to trick them . He then roughly grabs the Doctor . Wingford calls Cornelius off . Cornelius asks the Doctor if he can fix the plane or not . The Doctor says he can finish his calculations , but supplying the power needed to activate the drive system is something else entirely . The Doctor decides to stop fooling around and calls them out on the fact the craft isn ' t a plane at all , but an alien ship . Noting their confusion to his statement , he wonders if they didn ' t even know that they ' ve been working on repairing an alien ship , but realises there is some sort of perception barrier at work here . Cornelius recommends again that the Doctor should be submerged . The Doctor brings up the bodies in the water , with their blue skin . He asks them if their skin is blue under the makeup . Wingford asks him again , if he will complete the calculations . The Doctor says he might or might not . It depends on where the pilot of the ship is . He wonders if the pilot is the one controlling the people here . Suddenly , Wingford is speaking with another voice , making the Doctor realise he is now talking to the one controlling the people . The aliens tell him that the humans captured them and tortured them . They had to protect themselves , somehow , and chose to subjugate the humans . They have reached the limit of raw materials and expertise on the island that they could use to repair their ship . So , they accessed UNIT ' s files , and found out about the Doctor . They discovered that the Doctor was an alien , and thus believed that he would understand their suffering . While the Doctor understands , he doesn ' t condone their choice of subjugating the humans . They proclaim that they didn ' t harm any of the humans . The bodies in the water weren ' t dead , merely resting , being preserved by the cold water . The Doctor wonders why he should believe the aliens . They tell him that all they want to do is leave the planet and resume their voyage . The Doctor asks them to tell him about the voyage , but they are interrupted by a phone call . Wingford , now himself again , answers the phone . It ' s from the soldiers who were assigned to bring the special component to the island . Cornelius activates a monitor screen , allowing them to see the boat arriving , and allowing the Doctor to see the " component " and thus realise why the lorry was at UNIT HQ . The aliens have had the TARDIS brought to the island . Jo and Shedgerton have almost reached Level Zero , via climbing down . Jo asks why they didn ' t take the lift . Shedgerton tells her that doing so would have alerted whatever is down their to their impending arrival . However , he still can ' t remember what ' s on Level Zero , and Jo speculates that he may have been forced to forget via the blue liquid . The Doctor asks what happens now . Wingford tells him that he will complete the calculations . The Doctor asks him how he can be so sure that the Doctor will complete the calculations , now that he knows they ' ve stolen his TARDIS . Wingford proclaims they haven ' t stolen it , and instead have brought it to the Doctor . The Doctor realises they want him to use the TARDIS as the power source for their ship . Wingford states that they did everything they could to make him comfortable . The alien take control again and apologises for the bad food and drink , as they have little understanding of human ways , even though they ' ve been there since 1951 . The Doctor wonders why the aliens have to talk through humans . He wonders they don ' t just come out and speak to him directly . The Doctor admits that he knows the Brigadier wasn ' t really here . He knew something was wrong the moment Cornelius recognised him as the Doctor back at UNIT HQ . The Brigadier recognising his voice added to that . After all , the Doctor that ' s supposed to be there is the Third Doctor , not the Seventh Doctor . The aliens are confused at that . They know the Seventh Doctor is an alien , and must therefore be the Doctor . Cornelius asks him to finish the calculations . After that , he will be taken to the TARDIS . The Doctor refuses , not willing to comply until he knows that Jo is safe . Cornelius pulls out his gun and threatens the Doctor . The Doctor agrees to finish the calculations . Meanwhile , Jo and Shedgerton make it to Level Zero . Jo can ' t see anything , as it ' s very dark on this level . They hear the sound of the pipeline and follow it to its source , one of the aliens . As more of them arrive , Jo and Shedgerton make a run for it and begin heading up . Shedgerton wants to go all the way to the surface , in order to escape , but Jo wants to stay and find the Doctor . Shedgerton is consumed with escaping and thus runs off . Jo has no choice but to follow him . The aliens in Level Zero talk to each other and comment on how ugly humans are . The leader orders one of the others to chase after the two and kill them , before they can remind the other humans that they exist . The Doctor finishes the calculations and the alien thanks him for his help . The phone rings . Wingford , back in control , answers it . The TARDIS is now ashore , and both Wingford and Cornelius will take the Doctor to the TARDIS . The three leave the office . Shedgerton begins to remember more about that day in 1951 . The people pulled the ship out of the water and opened it up . Upon seeing the aliens , the humans reacted in fear and shot some of them . The surviving aliens were captured and experimented on . At some point , the aliens managed to get the upper hand and subjugated the humans . Jo hears a noise , which causes Shedgerton to remember that the aliens can fly . The two keep running , until they reach the water elevator . They get into the boat and trigger the elevator . As they start to rise , the alien following them emerges from the rising water , proclaiming that they can ' t escape and must die . Part four . The Doctor , Wingford , and Cornelius arrive at the water elevator and realise it ' s in use . Cornelius reverses the water flow , pulling the alien back down . Jo and Shedgerton manage to escape the water , before they can be pulled down . Cornelius opens the door , revealing the alien . Wingford and Cornelius are shocked at the sight , while the Doctor greets the alien . The Doctor notes the fact the alien can swim and fly , and then notes that he alien is now walking , meaning it ' s from a very adaptable species . The alien can ' t stand the sight of the Doctor , as he looks just like the ugly humans . The Doctor thinks the aliens just have a fear of human . The alien proclaims that fear is justified and tells the Doctor what the humans did to them . They had no choice but to subdue them . The blue liquid they used is a secretion they used back on their home world in order to control their food . When the Doctor comments on the fact that they turned the humans blue and kept them as young as they were in 1951 , the alien is confused . They didn ' t notice that the humans weren ' t ageing , as they did what they could to avoid looking at them . Jo and Shedgerton successfully climb out of the water elevator shaft and into a cave . Shedgerton has been feeling weaker as time has gone on , and Jo notices that most of the blue in his skin has faded away . Jo pulls out her transceiver and tries to contact Mike again , but fails to do so . The two head for the cave ' s exit . The alien leader informs the alien with the trio that the Doctor ' s calculations worked , and the power couplings have been aligned . The leader orders the other alien to escort the Doctor to the TARDIS . The alien orders Wingford and Cornelius to retrieve the boat . The Doctor notices how the secretion prevents Wingford and Cornelius from truly seeing and hearing the alien . The alien points out that these two were turned into prime units , with a stronger control over them . However , the secretion has been losing strength over time . Some of the workers are now barely compliant . The two soldiers force the Doctor to get into the boat . Jo and Shedgerton exit the cave and are now back on the surface . Jo tries again to contact Mike . Shedgerton suddenly collapses , having become weaker . The blue in his skin is almost completely gone now . His memories have now fully come back , and remembers the events occurred in 1951 , almost thirty years ago . The reason why Shedgerton is feeling weak is because he ' s started ageing . At that moment , Mike contacts Jo . Jo tells him about the aliens , but has to stop , because she can hear the sound of the elevator . The Doctor and his group have reached the top of the shaft and row to shore . Jo quickly tells Mike an invasion may soon happen . Mike tells Jo that he will bring soldiers to the island , to fight off the aliens . Jo notices that something is happening , and cuts off her communication with Mike . The Doctor wants the alien to tell him where they came from and where they plan to go . Otherwise , he won ' t help them . The aliens are from Europa , one of Jupiter ' s moons . The Doctor is surprised , as he didn ' t think there was life there . The Europan admits that there is probably no life there anymore , and this group of them is likely to be the last of their species . They tried surviving on Europa , but the conditions on it changed too much for them to handle , so they had to evacuate . The ship developed a fault as it passed by Earth , and thus crashed on it . The Europans never meant to come to Earth at all . They were planning to leave the solar system to find a new home world . They want to continue their journey , because they are sick of being on Earth . Jo and Shedgerton join them , with Jo questioning the Doctor on whether he can actually believe they are telling the truth . The alien proclaims they have no need to kill any humans . They just want the power so they can leave . The Doctor agrees to help them , despite Jo ' s protests . Meanwhile , Mike has gathered an army to take with him to Delphin Isle . He ' s prepared to fight against the alien invasion . The Doctor and the others arrive at the TARDIS . The Doctor has been wondering why he ' s been transplanted into an earlier part of his timeline . Maybe he was supposed to do something last time , when he was the Third Doctor , something he didn ' t do before . This may be a second chance for him . However , he ' s worried , as he lost his memories of these events after he arrived . Jo notices that the TARDIS is glowing . The Doctor realises that the Europans have tried to take the energy they need from the TARDIS , but have failed . The only way they can get the energy is with the Doctor ' s help . The Doctor points out a lot of suffering could ' ve been avoided if they had simply asked him for help , in the first place . Jo points out the he doesn ' t know what they plan to do with the power , and the Doctor agrees . For all he knows , they may plan to use the energy as a weapon for revenge against the humans . The Europan has had enough and orders Wingford and Cornelius to restrain Jo . Shedgerton attacks them and Jo breaks free . The Doctor speaks to the two soldiers , telling them to really look at Shedgerton and see what is happening to him . He points out that perhaps Shedgerton is already dead , having died years ago , along with everyone else on the island , including the two soldiers . The effect of the secretion is wearing off on them , and they ' re beginning to remember . The Doctor tells them to look at the alien . The two are finally able to perceive the alien . The Doctor opens the TARDIS door and everyone runs in , leaving the Europan outside . Inside the TARDIS , the Doctor closes the doors and ponders his options . The Europans contact the Doctor , telling him that their fate is in his hands now . Jo is convinced that the Doctor won ' t give them the power and reveals that UNIT is on the way here , much to the Doctor ' s horror . Jo calls out the Europans on their treatment of the humans on the island , but the Europans defend themselves . Their actions were only to insure that their species were to survive , as they are the last of their kind . Their mission was to find a new home world , which Jo takes to mean that Earth is their target . The Doctor disagrees , realising that the Europans are telling the truth . The Doctor tells Jo to contact Mike and call off the attack . She tries , but is unable to get through to him . Mike does notice Jo ' s attempts to communicate with him , but is unable to contact her . He takes it to mean that Jo and the Doctor are in trouble . The Doctor prepares to initiate the power transfer . Jo points out that if the ship were to take off , it would destroy the island , killing everyone still on it . Shedgerton points out that everyone may have died years ago , their bodies only still working now because of the secretion . Jo thinks sacrificing them to save the aliens is an inhuman thing to do . The Doctor agrees , it ' s just as inhuman as what the people on the island did to the Europans . Jo can ' t believe the Doctor is going to go through with this , as the Third Doctor never would make such a sacrifice . The Seventh Doctor points out that maybe that ' s why he ' s here now . They don ' t have time to evacuate any of the people , as UNIT is on the way . Jo tries to contact Mike again , but fails . The power signal from the Europan ship is blocking the transmission , meaning Jo will not be able to contact Mike . The Europans can ' t shut it down , as their ignition sequence is primed and ready . They need the Doctor to transfer the power now . It ' s their only chance of survival . The Doctor activates the power transfer , despite Jo ' s protests . Shedgerton draws Jo ' s attention to Wingford and Cornelius . Both are dead , having aged to death . Most of the people are probably dead by now . Shedgerton is only still alive now , because he was the youngest person on the island . However , he feels he doesn ' t have much time left . As far as he ' s concerned , the Doctor is doing the right thing . This is their punishment for what they did to the Europans . The Doctor realises he ' s made a mistake . He forgot that he is using the Third Doctor ' s TARDIS , which is missing certain modifications his own TARDIS has . The TARDIS can ' t regenerate her own energy fast enough to match the power transfer . The Europans are going to take every last bit of power , killing the TARDIS . Jo proclaims he can ' t let that happen , as the TARDIS is too important . The Doctor questions that , asking whether the TARDIS really is more important than saving the Europans . The Doctor is now more convinced that he was brought here to change a decision he made before , but he has no idea whether the one responsible is an ally or an enemy . If he knew that , he would know exactly what to do . The Europans contact the Doctor again , thanking him for his help . The Doctor wishes them luck . The Doctor sadly says goodbye to the TARDIS . Jo can ' t believe that the Doctor will let the TARDIS die and points out a problem . If the TARDIS dies here and now , then what will happen to the Seventh Doctor ? Will he even exist at all ? The Doctor agrees that this may change his timeline , or put it on the right track . Maybe he was brought here to repair his own history . Jo refuses to accept this , and quickly moves to the controls and shuts off the power transfer . An explosion rocks the island , knocking everyone to the floor . Jo recovers , wondering what has happened . She notices that the Doctor is no longer in the control room . Shedgerton tells her he went outside . She goes outside and sees that the island is falling apart . Jo was right about what would happen to the island . The Doctor tells her that when she cut off the power , it caused an engine imbalance , destroying the Europan ship . The Europans had weakened the structure of the island by mining all of the minerals from it . Jo apologises for what she did , only doing what she did to protect the Doctor and the TARDIS , and thinking about what the Third Doctor would ' ve done . The Doctor forgives her , as this was an impossible situation , with no right course of action . Jo asks him what will happen to him now . The Doctor doesn ' t know , but if things do go back to normal , and the timelines reset , then everyone will forget the Seventh Doctor was ever here , including Jo . Suddenly , they are confronted by the Europans , who escaped the ship before it blew up . The aliens are angry at what has happened and have decided that if they are going to die , then the Doctor and Jo will die with them . Before they can kill them , the Europans are killed by Mike and UNIT , who have arrived at the island , covering the Doctor and Jo in blue liquid . Jo quickly recovers and goes to locate the Doctor , being joined by Mike . She finds him laying on the ground in the liquid . However , it isn ' t the Seventh Doctor laying there . Instead it ' s the Third Doctor , but as far as Jo is concerned , nothing is wrong . The Seventh Doctor was right about the timelines resetting , and Jo no longer recalls the Seventh Doctor ever being there . Shedgerton joins them , having survived his ageing . He looks at the Third Doctor and asks who he is . Jo tells him it ' s the Doctor , confused about why Shedgerton doesn ' t recognise him . For a moment , Shedgerton is confused , but then his memories finish adjusting to the reset timeline , and he no longer recalls the Seventh Doctor either .