The place is Russia, sometime in the late 21st century. Lena Korolev returns from a shopping trip to the home she shares with her brother Alexi, but finds a strange man waiting for her instead. She identifies him as a ‘Sleeper’, but he rejects the derogatory name and insists that the work of the Somnus Foundation is about the awakening of mankind’s potential. He plays back a recorded message in which her brother complains that she’s been smothering him ever since their mother died and he has questions that only Somnus can answer. Lena suspects the group has brainwashed her brother, but he insists Alexi has simply taken a leap of faith and that she is too afraid to join him. He believes that when the human race ascends, the people of Somnus will be the vanguard and those like Lena will be left behind.

Inside the TARDIS, the Doctor is trying to investigate evidence of flux instability but he finds his work is obstructed by Turlough, who was rudely awoken while taking a nap. When the TARDIS begins to behave strangely, Turlough fears it’s another time corridor but the Doctor suggests it’s actually a phase shift, which means the ship has entered a zone of space-time with inherent causal discontinuities. They’ve arrived on Earth and although Turlough wants to go back to sleep, the Doctor insists that what’s happened outside is too dangerous to ignore.

The Doctor is delighted to discover the TARDIS has landed in Red Square, one of the most famous locations in Moscow. Even Turlough recognises their location from Lenin’s tomb. The last time the Doctor was here, it was one of the coldest October’s he’s ever experienced - even the blood on the streets had frozen. Unfortunately they’re stuck here until he can do some recalibrations, so he tells his friend to look out for anything out of the ordinary. Turlough suggests they use an enormous silver tower just behind the Kremlin to get a better vantage point, and the Doctor realises the building is based on a style of architecture that won’t be used by humans for at least another 600 years!

On the planet Ember, Tev orders the half-metal/half-flesh ‘husk’ of one of his people to be prepared. The psi-gate is opening and the displacement is almost complete. He detests humanity’s emotions and if the Migration wasn‘t so important he would have preferred to leave this work to the other custodians. He is sickened by the thought that one day it might be his own essence that is displaced. The process is completed and the ‘husk’ - now containing the mind of Alexi Korolev - cries out in agony, pleading for help. Tev regards him as nothing more than a disgusting animal who should be grateful that he was compatible with their race. Alexi panics when he realises he can’t feel his face, and Tev takes delight in showing him his reflection in the mirror. Alexi screams…

The Doctor and Turlough approach the huge glass building, which looks like a gigantic icicle set down in the middle of the city. It’s obvious that humans of this period wouldn’t have the technology to construct such a tower, so they decide to separate and walk around the perimeter to see what they can find. The Doctor is greeted by the automated voice of Qel, leader of the Somnus Foundation, who offers to answer any of his questions. The voice explains that Somnus knows the future of man. They believe in a manifest destiny for the human species where there are no deities and mankind will become their own gods, walking the stars and taking a form beyond flesh and blood. The Doctor argues that psychic transubstantiation is an extremely delicate business, then asks the voice if it is familiar with the Crystal Towers of Rigel VII, from an Earth Empire colony circa 2620. He remains dubious when Qel denies any knowledge of such a place.

Turlough notices that the Tower has no seams, as if it simply extruded out of somewhere. While he dreams of visiting somewhere tropical with lots of pretty girls, he hears Lena struggling as she is forcibly ejected from a back door of the building. She calls for help and, against his better judgement, he decides to intervene. As the guard threatens Turlough, the Doctor arrives and thanks him for finding their ‘friend’. The guard starts to follow them, but they are rescued by Lena’s friend Pavel Fedorin, who arrives in a delivery van. He very reluctantly agrees to let the two new strangers join them, but as they drive away, he warns Lena not to expect him to allow the strangers access to the ‘secure facility‘. Lena tells the Doctor and Turlough that she believes the Somnus Foundation are monsters!

Qel reads a report from the psi-gate and learns that Seo’s transfer was completed without incident. Her colleague Cord believes this is a sign that the evolution is ready to progress to the next stage and asks if he can soon be granted the honour of a true name, as Alexi Korolev was today. Qel assures him his time will come and acknowledges that he’s proven useful in helping humanity move closer to the point of change. Cord also tells her that Lena managed to penetrate the Tower earlier in the evening but she was apprehended in the Omnihedron Room. Qel asks him to make sure the woman does not draw any more undue attention to them, but this might be difficult as she had assistance from two unknown associates. Qel decides to run a Phase 1 test, this time using Lena’s mental template as a locus. As he’s about to leave, Cord casually mentions that an automated alert had been sent from her laboratory computer system. She is furious with him for not making this information his top priority - she’s been waiting for such a signal trace for years and may now miss her opportunity because of his laxity. She checks the signal and discovers the chronometric pattern is identical to the one she’s been waiting for. The TARDIS has arrived at last!

The Doctor, Turlough and Lena go for a cup of tea, while Pavel prefers to remain in his van as he feels too exposed whenever he goes outside. She thanks them for helping her and warns them they’ve made enemies of the Sleepers, a name she uses because the people from Somnus sleepwalk through their lives. She says they promise a better future, a Utopian Earth, but it’s all lies. She shows them a photograph of her younger brother and their late mother. The Doctor wants to take a look inside the Tower and reminds them that the Somnus Foundation welcome all visitors. Suddenly Lena feels a terrible pressure inside her head…as Qel activates Phase 1 and locks Lena’s aura type into the broadcast system. She orders the Unity Programme to be triggered at one quarter power, but kept localised as they don’t want a repeat of an earlier incident they had with a pack of mad dogs.

As Lena collapses, the birds in the area are driven into a frenzy and start attacking her. The Doctor leads everyone back to Pavel’s van and activates his Molenski Univarius, an all-purpose Time Lord Swiss Army knife, to create a subsonic pitch that causes maximum discomfort to the birds. Pavel tells them this is not the first time there have been attacks from feral cats, dogs and even packs of rodents. The government has been hushing it up, but there are more incidents every week. Pavel wants to take Lena home to receive medical treatment while the Doctor and Turlough return to the Tower. Pavel decides he can trust them now, and passes on the address of his secret bunker - which turns out to be his grandmother‘s basement.

The Doctor and Turlough enter the visitors’ reception area at the Somnus Tower and do their best not to get noticed. The Doctor is particularly intrigued by a ‘future history’ guided tour and he recommends Turlough use the time to find out what colour his aura is. Qel is preparing to evaluate the new group when Cord recognises Turlough from earlier. She suggests he give the boy a reading, so Cord approaches him and explains that the Somnus Foundation believes all humans emit a field of psychic energy and that a reading of that aura holds the key to understanding a person’s timeline, both the past and the future. However, he is confused by Turlough’s unusual readings, so he sends all the other visitors into the Omnihedron Room for refreshments while he restrains the youth.

The Doctor learns more of the Foundation’s predictions and takes delight in informing Qel that they’re off beam on human history by a sizeable amount. For example, their entry on the 49th century doesn’t mention the Fifth World War, and he’s also confused as to whether other entries refer to the Daleks or the Cybermen. Qel claims to be unfamiliar with those names, but at that moment Cord reveals the two visitors were the ones seen earlier with Lena Korolev. They are interrupted by the arrival of another man who introduces himself as Seo, but the Doctor recognises him from Lena’s photograph as her brother Alexi. Seo claims to have embraced a new name and taken his place as an honoured traveller of Somnus, but Turlough notices immediately that he appears to have lost his Russian accent. Seo and Qel argue over what to do with the intruders, but Qel overrules the new arrival, believing that as their questions has been answered satisfactorily they should be allowed to leave. When they are alone, Qel insists Seo stop trying to undermine her authority but he accuses her leadership of being weak. He hopes his arrival has come in time to ensure the safety of the evolution.

The temporal inversion starts to die down, although the Doctor and Turlough are left feeling sick. The effect was much stronger than when the TARDIS first landed, which indicates the problem is getting worse. No one else seems to have noticed anything untoward, but their previous exposure to the time vortex has made them both sensitive to such things. They’re in the midst of a time fracture, the formation of a branch point where history is about to diverge from its natural course. It’s even worse than it sounds - changing Earth’s history now will ripple out into the time stream and have consequences on an intergalactic scale. The Doctor admits he suspected this was happening, which is why he brought them to this place and time.

Qel wonders if she’s slaved away for years on this pitiful wasteland for nothing. Just as her goal is within her grasp, Seo has arrived and the millennium on Ember has clearly made him more arrogant than ever. But however much she hates him, she also realises the evolution would be nothing without him. The Phase 1 experiments have shown a level of success well above her predictions and she’s encouraged by evidence of artron energy within the city limits. Seo demands entry into her private quarters and accuses her of creating a cult of apathetic barbarians while their brethren have remained lost in the future. He examines the data Cord gave her earlier and he recognises the signs of a Time Lord’s presence. He accuses her of withholding this information from him and Qel reveals that the blond haired visitor they met earlier that night is the Doctor in one of his early corporeal incarnations. She knows the Doctor will not be able to resist the temptation to return later to rescue ‘Alexi’, and when he does he will pay a million times over for the Time Lords’ betrayal of their species!

Pavel is checking some underground websites from his basement, but there are no records of anything odd going on except a weird blue box seen in Red Square. He finds no records on their new friends either, although there is a history of different faces using the Doctor’s alias. Just then the Doctor and Turlough arrive and give Lena the bad news about her brother. Pavel explains he was friends with the Korolevs when they were children, but his interest now is in investigating conspiracies and the dark edges of the unknown.

Pavel tells the Doctor he found a report about Somnus that showed every one of their arbiters displays uncommon intelligence and strong personal charisma, but in each case those qualities manifested overnight. The two reporters who compiled the article later died in suspicious circumstances. Pavel suspects the Sleepers bought up all the old KGB technology after the old regime fell. He names Natalia Pushkin as the leader of the Somnus cult, who now goes under the name of Qel, High Priestess of the New Consciousness. The Foundation had originally been a legitimate research group studying sleep disorders and neuro science, but they gradually turned Pushkin’s crackpot visions into a global cult. The rumours say she was conducting secret research into psychic potential on behalf of the military. Eleven years ago there was a huge electrical storm and the Foundation’s clinic was burned to the ground, killing dozens of patients.

Turlough comforts Lena outside. She says she is lonely and disconnected, something Turlough understands. She’d promised her mother she would look after Alexi and she feels she’s broken her word. When they return to the others, Turlough suggests going back to the clinic for more clues…

The ‘real’ Alexi Korolev finds he has been displaced to the barren planet Ember, along with other people whose bodies have been taken by the Somnus. Here, everything that made Alexi what he was is contained within a body of metal and bone, while back on Earth his true form is been used by one of this planet’s original inhabitants. The guard Tev treats the humans with contempt, regarding them only as savages to be exploited as they wish, and keeping them in check with painful stings tapped from his psychic energy. Alexi meets the real Natalia Pushkin who’s been a prisoner for years and is now well versed in briefing new arrivals. In this period of time, Earth is nothing more than ashes. The planet Ember is cold and black and there is now only one surviving star, kept alive by force. This is entropy, the death of the Universe! Even as they speak, Tev is preparing another of his kindred for transition into the body of an innocent man.

The Doctor invites Lena and Pavel to join him and Turlough inside the TARDIS, but as he prepares to take off, the Doctor discovers a distortion grid surrounding the Somnus Tower which prevents them from landing inside the building. Instead, he takes them back eleven years to the night the Foundation clinic was burned down. At first their guests believe it is some sort of trick using holograms, but it slowly dawns on them that they’ve travelled back in time. Lena rushes off in shock and when Turlough goes after her, she reveals that this is the night her mother died. If she can prevent that happening, Alexi will never want to join up with the Somnus in the first place.

As they approach the forbidding Foundation clinic, the Doctor explains that metacognitive imprinting on the brickwork from all the years of negative emotion and mental suffering has caused a sort of psychic stain, which is why people always feel uncomfortable in hospitals. Inside they discover a scene straight out of a Victorian madhouse, with six patients hooked up to electromagnetic resonance projectors and quantum image detectors. Each of the patients has an near identical waveform, suggesting the Sleepers have been deliberately modifying their brain chemistry. This is an early test of Phase 1, intended to adjust organic brains so that the patients’ unique electromagnetic signatures become uniform. In theory this could induce artificial telepathy between them, but the Doctor thinks there’s more to it than that. Earth’s atmosphere has its own signature called the Schuman resonance, and the Sleepers are trying to match human minds to it to create a group consciousness, one single huge psychic entity. This would mean the death of individuality, and the Doctor knows the human race would never be able to survive that. Humans thrive on conflict and struggle, and premature godhood would remove the will to endure and turn the entire race into a singularity!

Turlough and Lena shelter from the rain. She still intends to carry out her plan, despite Turlough’s warning about changing history. He struggles to answer her questions about the moral high ground, but he points out that time doesn’t care about individual people. If she saves her mother, someone else will have to die to balance things out. Lena feels broken inside and accepts that she can’t do it.

Pavel offers to look inside the minds of the poor wretches in the hospital and the Doctor agrees to wire him up to them. Pavel begins to speak with the voice of unity and explains that Pushkin became Qel after she opened the psyche of the Somnus. They have the ability to see all potential probabilities and were seeking compatible minds in order to shift human life from the physical to the metaphor. There will be an evolutionary quantum leap on an astronomical scale, changing flesh and blood to non-corporeal existence in the blink of an eye and creating a singularity with godlike abilities. The Somnus cannot return to Ember, a name the Doctor vaguely remembers, but they knew he would come there eventually and he is to be their catalyst.

The TARDIS returns to Lena and Pavel’s time, but in the secret bunker rather than Red Square to be less conspicuous. As the Doctor uses a dermal regenerator to repair his injury, the group debate whether their trip to the past achieved anything worthwhile or whether history was changed in any way. Lena accuses the Doctor of making more messes than he cleans up and wonders what other disasters throughout history he might be responsible for. She storms out angrily and the Doctor decides to follow her as he feels he owes her an explanation.

Seo mocks Qel for letting the Gallifreyan slip through her fingers for a second time, but she claims she allowed him to walk free from the Tower for a reason. She points out that of the two of them, she was the one working for the last decade in a primitive backward century, but he argues that while she enjoyed the sustenance and comfort of Earth he was shivering in the cold void, trapped in the End Time. At least he was lucky that she found a human subject with a compatible aura type for him - others of their kind have not been so fortunate. They are interrupted by an alert telling her a chronometric particle discharge has been detected in the city, which means the TARDIS has returned, and this time they know precisely where the craft has landed. She orders Cord to assemble a capture team.

Lena telephones the Somnus Foundation and is about to hand over the time travellers in return for her brother when the Doctor catches up with her. He understands her dilemma and knows that families compel people to make choices they never usually would. He too has a family of sorts, and every time one of them leaves he ages a century or so, but he accepts that’s the nature of things. Lena and the Doctor find themselves in a funfair that she and Alexi used to visit every year when they were small. The Doctor asks Lena to tell her more about what happened on the night her mother died and she explains that her mother had cancer and was in a lot of pain. Lena wanted so much to help her that when the storm blacked out the hospital she broke in and turned off the equipment keeping her mother alive. Although Alexi never knew what she did, she feels she can no longer carry the guilt of her memories on her own now that he‘s gone.

Pavel asks Turlough to tell him about alien worlds, but Turlough says things aren’t that much different. Wherever you go there is good and bad, dark and light. Suddenly the alarm sounds and the bunker entrance explodes. Across the square the Doctor and Lena hear the noise and rush to help. Turlough finds himself confronted by Cord and his guards, who secure the TARDIS and prepare to take it away. Cord notes Turlough’s unusual aura and decides to take him with as well, leaving Pavel behind in the ruins of the bunker. Moments later the Doctor and Lena arrive and try to help Pavel out of the rubble, but his injuries are too severe and he dies. As they leave, the remains of the building collapse behind them.

Seo tells Qel that the death of a Time Lord is not pleasant, especially if they have incarnations still unused. Qel is disturbed by the way he relishes the prospect and believes her people have not changed in millennia, it is still their hate that keeps them warm. Seo says hate is all the Time Lords left them with. Qel is concerned that after all this time they’re having the same arguments and the same conflicts. Humans are still decades away from developing the power the Sleepers need to trigger their evolutionary plans, but if she can use Gallifreyan technology, the singularity will rise in hours rather than years. Cord returns with the TARDIS and Turlough and Seo finally realises this was part of Qel’s plans all along.

Qel and Seo watch as a phase array is directed at the TARDIS. Although the ship appears to be in pain, the discharge is insufficient to have any effect, so Qel orders the level to be stepped up. Seo wants to give Turlough the gift of a true name, but Cord is worried there might be complications due to the anomalous factors in his aura scan. He is overruled and the conduit to Ember is opened. Turlough screams in agony…

As the Doctor and Lena cross the city, the Time Lord feels a momentary stab of agony and realises the TARDIS is being tortured. The time fracture is happening again and the Tower starts to glow. Everyone around them is suddenly frozen like statues, indicating that the Sleepers are broadcasting their influence over the city and the singularity is beginning to form. The Doctor realises the Sleepers’ plans are more advanced that he thought - Moscow is now under their control and before long, all life on Earth will share one consciousness. Using his Univarius again to temporarily help Lena by jamming the signal, he explains that if you have enough psyches in close proximity you can pass the point of critical mass; flesh becomes energy, the mind breaks free of matter - instant evolution! Before long humanity will begin colonising other worlds and the race would be spread too thin to create a Singularity. The Sleepers have chosen this time and place very carefully. The Doctor has been able to resist the voices in everyone’s heads so far because his mind is too distinctive to be drawn into the consciousness. He helps Lena down into the Moscow Metro where the automated trains are still running, but she starts to succumb to the voices. Eventually the appeal of joining minds with Alexi becomes too strong for her to resist.

On Ember, Tev is furious at having to administer the repulsive process of displacement once again. Before long, Turlough has been successfully transferred through to the alien planet and his mind now inhabits one of the half-metal/half-flesh ’husks’. The shocked youth resists Tev’s orders and receives an energy sting in response. Alexi helps Turlough to his feet and is pleased to hear news of his sister. They are joined by the real Natalia who tells them they’re on a planet beyond the edge of the Spinward Deeps, trillions of years into their future. Their abductors have abandoned them there with a ring side seat to view the heat death of the Universe. Turlough realises that back in Moscow one of the aliens is now walking around wearing his skin. His new body is weak and feeble, patched together with rusting metal. Although Alexi was only taken a day ago, he’s been on this planet for weeks because time moves differently on Ember, in fits and starts. The laws of causality are decaying, just like everything else. Slowly it dawns on Turlough that the Sleepers have devised a method of dominating human minds…but he’s not human!

The Doctor is subdued before he can attempt any action. Qel taunts him by observing that the most pain she can cause him is making him watch his greatest failure unfold before his eyes. Seo can sense the city is now completely under their control. They will obliterate the future and humankind will thank them for it.

Turlough and his new friends view the desolate, endlessly bleak surface of Ember and are amazed to think that people once lived there. It was outpost once, an observatory from which the Sleepers could watch the galaxies for signs of intelligence. Although they can understand the atrocities committed in the name of survival, they refuse to excuse the Sleepers’ actions. Turlough realises the aliens seed apathy like a virus and most of their fellow abductees have given up, accepting their defeat. When he discovers the aliens find close contact with humans distasteful and are physically repulsed by their thoughts, he suggests they use this fact to make their captors ill. He starts to rally support from the others.

The Doctor tells Qel and Seo that their takeover is already destined to fail and he is only there to minimise any collateral damage. Cord energises the psi-gate and the TARDIS starts to show signs of distress as they siphon off the raw flux from the central column. For the first time, the Sleepers will be able to bring their people across from Ember in one great exodus. Then they plan to join the singularity and help guide it as a godhead. When the Doctor questions their right, they reveal that they are actually human themselves - they are the last descendents of mankind, the final remnants of this planet’s children. They are fleeing entropy and are invading their own planet of origin after they were betrayed and cast out by the Time Lords, who knew that the end of the Universe was coming and opened up a gateway to another realm to save themselves and anyone else they deemed worthy, while abandoning the human race to perish.

Turlough and the others find a chamber full of rusting bodies, people who were killed by multiple stings after showing signs of rebellion. It is one of hundreds of similar chambers used by their captors as receiving stations for displacements like themselves, but controlled from the Core, the last source of energy in the Universe. Turlough believes they must be able to make the trip back if they can operate the right controls. Natalia leads them to the Core, a sickly light that’s not meant to exist in our reality and is difficult for the eyes to focus on. Suddenly Tev arrives and attacks them, but Turlough picks up a metal rod and smashes the Core. Unfortunately, it does not have the effect he expected and all the humans find themselves paralysed, overcome by a powerful noise inside their heads.

The Doctor accuses the Sleepers of attempting vengeance for something that won’t happen for billions of years, but for them it already has happened. Art, culture and knowledge have all disappeared, simply because the Time Lords deemed them undeserving. They always wondered whether the Doctor knew and why he did nothing to warn them - did he always regard humanity as pets, something to amuse himself with? He assures them he would have no part in that and he can’t be held accountable for events that haven’t occurred yet. But they still blame him, and once the singularity is complete, the entire human race will unit to share in the pleasure of punishing him.

Turlough enters the room and the Doctor realises straight away that it isn’t his friend, just another Sleeper using his body. This is Xen, and his role is to monitor the energy projector to maintain the stability of the Shuman resonance. When Qel declares that she will lead the singularity to forge a new future, the Doctor points out that the whole point of a group consciousness is that no individual will be in charge. Their control panel indicates a distortion in the conduit, suggesting there’s a problem back on Ember. Qel tries to compensate and once again Seo challenges her leadership and hints that it may be time for him to overrule her and take a more direct role.

Back on Ember, Tev is enjoying the agony of Turlough and his friends - and then realises that the youth’s mind is somehow different to the others. He moves to kill Turlough, but Natalia intervenes. Suddenly everyone’s minds are filled with the despair from her memories and she focuses it on Tev who is unable to cope with her discord. The Sleepers are so cold they’ve forgotten how to feel pain and passion and they can’t handle the psychic fallout of raw human emotions. Turlough joins in and forces Tev to look into his mind and see all the friends he’s lost, the pain and torment of being torn from his homeworld and family, all the murder and destruction he’s seen… Alexi and the others do the same and eventually Tev dies.

The power Core on Ember is destabilising and the Sleepers foresee their grand plans in ruin. They cannot proceed to Phase 3 totality unless the resonance becomes stable. Seo demands that the psi-gate is opened so that he can merge with the singularity and take direct control from within. Qel refuses to allow it and the Doctor prompts her to take control herself rather than hand over to her rival, even suggesting that Seo may have engineered the problem himself for this very reason. Qel orders Seo to be restrained, but during the confusion the Doctor manages to reach the psi-gate controls and operate it.

The Doctor finds himself within the singularity. He calls out to Turlough, who can hear him in his mind across time and space. Technically everyone is now able to read everyone else’s minds. Alexi Korolev is also with them, as is Natalia and the others, and for the first time Alexi is able to go inside his sister’s thoughts and discover the truth about their mother’s death. The Doctor tells them he has released the Sleepers’ control over the psi-gate and they can follow the sound of his voice to return home. Turlough is able to see the path and leads the others back to reality.

Back in the Somnus Tower, the Sleepers realise the psi-gate is disintegrating and the singularity will not be able to hold. Qel is horrified with the Doctor for destroying her work - and one by one the Sleepers start to hear the voices of their body’s original owners in their heads. Their ancestors, who they’ve callously abused, are about to take back their bodies and return the Sleepers to Ember. Qel wants revenge, and she orders Xen to sever the conduit, destroying the minds of those they have taken and scattering them across the time stream. But Xen starts to struggle against Turlough, who is fighting to return back to his body. Even as their plans collapse around them, Qel and Seo blame each other and start to fight…until Alexi returns to take his body back from Seo.

The Tower is about to blow apart from the energy release of the collapsing psi-gate mechanism, but the Doctor refuses to leave until all the displaced humans have returned to their normal bodies on Earth. Only Natalia is left, but she is unwilling to let Qel escape to freedom back on her home world, even though the planet is dying. She urges the Doctor to escape while she sacrifices herself, holding Qel in the Tower to await both their deaths. Leaving the TARDIS behind, the Doctor joins the others as they flee the building.

The Somnus Tower explodes, showering everyone below with glass and masonry. Alexi Korolev wakes up in a hospital tent, having been knocked out for several hours. Turlough assures him the whole experience was not just an insane dream. In fact, he and the Doctor are now trapped on Earth as the TARDIS was destroyed in the explosion too. Alexi is reunited with a very grateful Lena and, at the Doctor’s request, they agree to look after Pavel’s grandmother. The Doctor and Turlough make their excuses

Moscow 9 News reports that the National Police Directorate have issued a statement saying the Tower was destroyed by an unprovoked terrorist attack from a group opposed to the Somnus religious cult. They also declare that the terrorists released an hallucinogenic compound into the water supply, causing temporary mass hysteria among the population.

The Doctor buys Turlough a cup of tea and they go for a walk. They‘re reassured to see that the city is starting to return to normal and the conversation gets round to what they’re going to do now they‘re stranded. The Doctor reminds his friend that at this time in Earth’s history there are actually dozens of time travellers or aliens scattered around the planet (he even points one out who walks past them), but he has an even bigger surprise for Turlough - the TARDIS materialises in front of them, having escaped its entrapment a split second before the explosion. The ship took a century or two off to recouperate, then came back to pick them up. Turlough wonders why the Doctor bothers to get involved if fate is already cast in stone, but the Time Lord replies that only the broad strokes are laid down. It’s the moments between the ticks of the clock that life truly thrives and where they can make a difference. He’s confident there will be someone to watch over the Sleepers - the last humans - during their final moments.