The Defectors (audio story)

 was the 198th story in Big Finish Productions' Doctor Who monthly range. The beginning of the "Locum Doctors" trilogy, it partnered the Seventh Doctor with Third Doctor companion Jo Grant.

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?

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 soldiers 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 the Doctor outside the room. However, instead of it being the Third Doctor, the Seventh Doctor is the one who is standing there.

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, the Doctor 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 Lords. Jo is suspicious now, questioning whether this strange man in front of her really is the Doctor.

Cornelius joins the conversation, somehow recognizing 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 Island, 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. They pretend to enjoy it to keep the pub owners at ease. After the meal, the two are taken upstairs to their bedrooms 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 boats 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 realize 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 recognizes 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 their files 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 recognized him as the Doctor back at UNIT HQ. The Brigadier recognizing 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 aging, 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, having escaped the boat when the water flow was reversed. 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 pints 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 aging. 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 Island. 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 in the TARDIS 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 even here, including Jo.

Suddenly, they are confronted by the Europans, who escaped the ship before it blew. 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 aging. 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.

Cast

 * The Doctor - Sylvester McCoy
 * Jo Grant - Katy Manning
 * Captain Yates - Richard Franklin
 * Captain Cornelius - Neil Roberts
 * Commander Wingford - Barnaby Edwards
 * Shedgerton - David Graham
 * Europan Leader - Rachel Bavidge
 * Europan - Jez Fielder

Uncredited

 * Brigadier Lethbridge-Stewart - Nicholas Courtney (archive recording)

Continuity

 * Jo tests the Doctor by asking him why his first three incarnations were brought together. (TV: The Three Doctors) She also tests him by asking him on which planet did she pretend to be a princess. (TV: The Curse of Peladon)