It begins on a glorious summer afternoon in a traditional suburban street, complete with ice-cream van playing ’Greensleeves’. The snooker is on the television and young Tom Braudy’s Nan is knitting in the corner. She asks Tom what he’s building and he says he’s making a spaceship from Lego. She seems surprised they make Space Lego, but of course it’s not for girls because they only want to make hairdressers and flower shops, not rockets and satellites. Last week Tom built a ship to go to Mars, but today he’s building one for Jupiter because it’s a bigger planet so you need a bigger ship. Suddenly the television fills with static and the snooker is replaced by what appears to be footage from inside a real spaceship. Mrs Braudy tries to change channels, but it’s on every side. The pictures show some kind of disaster taking place, with the astronauts struggling to reach the escape pods before the ship crashes. The snooker returns and Tom wants to see more, but it’s gone now. Tom goes outside to ride his bike and Mrs Braudy reminds him his dinner will be ready in a minute, so he’d better not be long.

The TARDIS materialises and the Doctor, Charley and C’rizz emerge into Mrs Braudy’s living room. They were expecting to be in the countryside, but before they can work out what’s gone wrong, Mrs Braudy asks them to move aside as they’re blocking the television. The Doctor is delighted to find the snooker is on as he’s a fan of players who go for big breaks. Charley apologises for interrupting her viewing and she introduces her companions. They decide to leave, but Mrs Braudy offers them a cup of tea and the Doctor gratefully accepts. C’rizz can’t understand why he wants to stay, but the Doctor points out it would be impolite to turn down an offer of tea - that’s how wars start. It’s happened on at least fourteen occasions if his memory is correct, but Charley challenges him to provide documented evidence when they return to the TARDIS. He admits that maybe it wasn’t quite fourteen. Charley is more interested in why Mrs Braudy doesn’t seem surprised by their arrival - and particularly C’rizz’s appearance. They hear the ice-cream van outside so they decide to pop out.

Outside, the ice-cream van pulls up. The Doctor goes to buy something, but young Tom gets to the front of the queue first and orders a Mr Whippy with a flake. When it’s the Doctor’s turn, the ice-cream man seems surprised as he’s never seen him around here before. He explains that’s he’s visiting Mrs Braudy for a cup of tea, then he orders a Sky Ray lolly. The nearest thing they have to that is a Zoom, but unfortunately it doesn’t come with the trading cards. Charley and C’rizz turn down the offer, but the Doctor persuades them to change their minds. He notices that the ice-cream man doesn’t know much about his own stock and wonders if he’s new at the job, by the man denies this.

As they walk off, Charley comments on how dreary the street looks. All the houses look the same - in fact, they’re all identical, with exactly the same gardens and curtains. The Doctor tells her she’s just not paying enough attention, so she challenges him to point out Mrs Braudy’s house. He thinks this will be easy, but when he takes a closer look he can’t be sure. C’rizz has also noticed that the street is so long, you can’t actually see the end! Things are obviously not normal here, so they decide to head back to the TARDIS … but they all disagree about which direction they came from.

The Doctor, Charley and C’rizz ring the bell of a nearby house and are delighted when Mrs Braudy opens the door. Unfortunately when they tell her they’ve come to collect their police box, she doesn’t know what they’re talking about. She denies having met them before and says she hasn’t seen anyone all day except for her grandson. The Doctor introduces himself and politely asks if he can see inside her house. She doesn’t mind so they go in - but there’s no TARDIS there! Although this house is exactly the same as the one they arrived in, they soon realise this isn’t the same house or the same Mrs Braudy. They ask her whether she knows much about her neighbours, but she doesn’t know them. She offers them a cup of tea, but they gratefully decline and leave.

The travellers decide to split up, so they all chose different parts of the street and ring on the doorbells. In each case, they are greeted by another Mrs Braudy and in each case, the elderly woman denies ever having seen either them or their police box before. The Doctor notices that his Mrs Braudy is watching scenes inside a spaceship on her television. She tells him it’s supposed to be the snooker but it seems to have been replaced by some space adventure programme. She offers him a cup of tea, which he accepts… Neither Charley nor C’rizz are having any luck, but the Doctor has decided to see what’s round the back of his Mrs Braudy’s house. He peers over the garden wall but it backs right on to the next street - where he finds yet another Mrs Braudy in her garden. Frustrated, he returns his attention to the spaceship scene on the television…

C’rizz rings on the next doorbell and Mrs Braudy answers, but before they can talk, another voice calls out from the living room. Mrs Braudy introduces C’rizz to her other visitors, and he’s astonished to discover the other woman is one of the two astronauts who appears in the spaceship footage on the television. Mrs Braudy assumes the woman is an actress and wonders what she might have seen her in before? When she goes to get some biscuits, the astronaut pulls out a strange looking gun and tells C’rizz not to move! She demands he tells her how she can get Tom Braudy out of there, but C’rizz doesn’t even know who Tom is. Frustrated by his lack of co-operation, the astronaut shoots C’rizz and tells the returning Mrs Braudy that he just fainted. She offers to take him home and uses a device that lifts C’rizz off the floor…

Charley rings on the next doorbell and is surprised when Tom Braudy answers. He invites her in and introduces her to his grandmother, Mrs Braudy. Charley is shocked because Tom is clearly far too old to be her grandson, especially when Mrs Braudy tells her she is 66 years old. She claims that Tom is ten, yet it’s obvious to Charley that he’s much older than that. Mrs Braudy invites her to stay for dinner as they’re having fish fingers. As Tom tells Charley he’s building a spaceship to go to Jupiter, the doorbell rings again. It’s the Doctor, which is odd as they both thought the other was on the opposite side of the street. Things get even more exasperating when the Doctor meets Tom again - because as he now recognises him as the second astronaut in the space footage being shown on the TV.

Another version of Mrs Braudy is showing the ice-cream man the TARDIS in her living room. He doesn’t recognise it and she assumes this is because police boxes existed a little bit before his time. She tells him it just appeared, then she offers him a cup of tea. The ice-cream man becomes angry and asks if the police box has anything to do with the new arrivals, but she doesn’t seem particularly interested so he decides to load the box on the back of his van.

The woman astronaut wakes C’rizz up and he finds himself chained up aboard her spaceship. She introduces herself as Kim Krotonska, a commander in the Commonwealth Space Programme, a project that she admits is basically just a lot of British money being spent on firing off rockets from the middle of the Outback. C’rizz assumes this means they’re still on Earth, but Kim points out this was never Earth. She asks him again how she can get Tom out of there, but he still doesn’t know what she’s talking about. She produces the gun and says if he doesn’t help her, she’ll kill him!

C’rizz tells Kim he’s not afraid of dying, but she points out that’s not the same thing as not wanting to die! She warns him not to bother trying to escape as his cuffs are made of bonded polycarbide, but he successfully manages to break free anyway and they struggle for the gun. He disarms her and discovers, to his amazement, that the gun plays the tune ’Greensleeves’ whenever it’s activated. He wants to know where they are and when she seems surprised by his question he admits that they arrived here by accident. She doesn’t know the name of the planet but the aliens who live here are able to change their form at will. She’s been hiding her spaceship in the attic of Mrs Braudy’s house for three months. He finds this hard to believe and she explains that this place can reshape itself. When she tried to warp-jump her way out, she ended up in the attic and the house stretched itself to accommodate the ship. The whole street is a prison cell - try to escape and you just get bounced straight back again! She explains that she’s been transmitting signals into the TV set in the house…

Tom and Charley are too engrossed playing with Lego to watch the repeat of the spaceship footage featuring the two astronauts on the TV set. Charley still wants to know what the Doctor plans to do about the TARDIS and he clarifies that when he said the ice-cream van vanished into the distance, he meant it literally. It didn’t drive out of sight, it reached a certain point then faded away. The ice-cream van is obviously the way in and out of this place so if it comes around again, they might have a chance. Tom shows Charley his toy astronauts - he’s the one in red and the others are called Samuel and Kim. He claims to have made the names up, but the Doctor notices that one of the astronauts on the TV is called Samuel. In the programme, the two astronauts talk about their colleague Samuel who died when he was ripped down the middle by some sort of creature. Charley asks where the pictures are coming from and the Doctor says he doesn’t think they’re watching a science-fiction programme - it’s footage of something that really happened. The ship the astronauts are in is a genuine ion-jet rocket of the 21st century that won’t come into use for another 35 years. The footage also shows something called a Marmadon, a race of foul creatures that live in deep space. Not only is the monster on the screen far too realistic to be CGI, no one on Earth during this time has ever heard of them! He believes the footage is from a black box recording, taken from a genuine space expedition.

The footage is obviously on a loop because the Doctor recognises the next bit, so he explains the whole story to Charley. The crew of the ship went into cryogenic sleep for a mission to Jupiter. There was a systems failure, the ship drifted off course and they didn’t wake up. More than a hundred years later, the Marmadon broke in to loot the ship and then the crew woke up. Two of the astronauts escaped, but unfortunately Samuel wasn’t so lucky…

The ice-cream man, named Lest, reports back to his leader and describes the tall blue box he found in the street. It’s significant because Lest hasn’t seen either it or the other creatures who are roaming around before. His leader, Argot, reminds him that the cell projects creatures from the captive’s imagination all the time, but Lest assures him he hasn’t forgotten that fact, but usually they’re the same people - these ones are new. Argot reminds him that he made similar claims once before, but no evidence was ever found, but Lest is certain he wasn’t wrong on that occasion either. Argot is busy with their accountant, but he promises to deal with the matter when he returns.

The TV shows a recording of the male astronaut broadcasting a warning - he’s apologising for the fact that there’s nothing he can do to stop the ship crashing into a populated area… Then the clip ends and the TV returns to its normal snooker coverage. The Doctor tells Charley that the story concluded when the two astronauts abandoned the ship. The female, Kim, was trying to get back to Earth, which by then was light-years away, while the male astronaut - who is clearly Tom - crashed into another planet. The question is, why is Tom now at his grandmother’s house playing with Lego and acting as though he was ten years old? Mrs Braudy obviously doesn’t realise Tom is the astronaut in the footage on the television because she doesn’t recognise him as a grown man. The Doctor decides to find C’rizz, while Charley and Tom sit down to eat their fish fingers…

C’rizz has also been briefed on the astronauts’ story and he asks Kim if she ever got back to Earth. She says she did eventually - 227 years after she left! By then everyone assumed they were long dead so she became a bit of a celebrity, doing talk shows and game shows, she even had a bit of a pop career. But it was the hardest time she knew as she couldn’t get people to treat her normally. When she realised the ships they were building now were so much faster than in her day, she knew she could return to this planet in a few months rather than a hundred years. She decided to return to find Tom by tracking down the distress signal from his black box, but when she came down to look she became as stuck as he is, only in the attic. Now that she’s here, the ship won’t navigate properly any more. She knows it’s a prison because she’s seen the jailors, although fortunately they don’t know about her yet. The cell is built around Tom’s personal experiences like a virtual reality. Tom thinks he’s a child and he hasn’t aged a day even though he must have been here for decades. Unfortunately he doesn’t recognise her despite her trying to jog his memory by showing the old footage on his TV set. She tried to bring him up to the attic but for some reason he was physically unable to pass through the airlock, even when he was unconscious. She tried to avoid going outside because there’s something in the air. You can’t see it, but it gets inside your head and tries to trap you. It almost got her the first time, but she’s got ‘medical defences’ aboard her ship. C’rizz is worried about Charley and the Doctor as they’ve been exposed for a few hours by now, so Kim offers to help.

Charley and Tom fight over the last remaining fish finger so Mrs Braudy cuts it in half. The phone rings - it’s Charley’s mother telling her to come home! Charley can’t believe it at first, then agrees it’s time to go. Her mother will be waiting for her at the gate, but she’s has forgotten where her home is. Mrs Braudy gently reminds her that it’s the big house at the end of the street. She opens the front door and points to an Edwardian family manor house just across the road. Charley thanks Mrs Braudy for having her and she says it was no trouble - it’s nice for Tom to have some friends his own age!

Charley crosses the road and Lady Louisa Pollard admonishes her for running in a very un-ladylike manner, before proceeding to test her with literary quotations. Charley wants to play outside, but her mother tells her she’s already been gone for hours. When she asks what she’s been up to, Charley can only remember making airships with Tom, but her mother doesn’t think its appropriate for her to be playing with boys until she’s older. Nice as he may be, Tom simply isn’t from their class.

As they leave Mrs Braudy’s house, Kim ties some string to the gate so she knows which one contains her ship. C’rizz spots Charley at the gate of a big house which wasn’t there earlier. Kim recalls that when she started to get absorbed into the cell, she found herself in the flat she shared when she was a student. The only way to snap out of it is for your brain to latch onto something from outside that frame of reference. She was only saved because she was listening to her iPod. They call out to Charley, much to her mother’s indignation. At first Charley doesn’t recognise C’rizz, but this makes her wonder what her house is doing there and she promptly vomits out the stuff that got inside her head. Fortunately it doesn’t taste too bad. Lady Louisa orders them to leave, believing them to be gypsies, but by now Charley has realised her mother is just an illusion. As Lady Louisa returns to the house to call the police, the Doctor joins them, also coughing up - although in his case it’s because a mouthful of tea went down the wrong way. He spots the incongruity of Charley’s home in the middle of a 1930s terrace and Kim suggests they go back to her ship. The Doctor recognises her instantly from the telly!

Tom tells his Nan that his toy spaceship has been held up because of a fault in the auxiliary engine which was discovered during the final round of tests. It’s been set back a week while they run further diagnostics. As Mrs Braudy admires his vivid imagination, Tom assures her it all happened for real.

Kim takes the Doctor and the others back to her ship in the attic of Mrs Braudy’s house. The Doctor asks Charley to stall Kim while he takes a look around unobserved. The Doctor tells C’rizz that he’s owed an apology after his companions mocked him for landing back on Earth (yet again!) instead of their planned destination, the planet Lucentra. The Doctor is convinced that they are indeed on Lucentra, partly because Kim’s flight logs indicate that, but also because he examined the stuff Charley coughed up and discovered the technology is based on nano-forms, tiny limited-intelligence creatures with specific roles hardwired in. These creatures are usually made in their creators’ image and he knows enough about Lucentrans to recognise one. Kim is absolutely right about the prison cells and, in fact, the Doctor’s seen such controversial techniques used before. The prisoner doesn’t even realise he’s a prisoner - he regresses to safe, happy time in his life where he’s docile. Although it may be more humane than locking someone up in a tiny cell, it’s morally wrong to take away a person‘s self-knowledge.

The Doctor starts reprogramming Kim’s iPods with a mix of outside sources to keep their minds active. He’s not sure what to make of Kim yet, but C’rizz thinks she’s judgemental and selfish. He doesn’t think coming here to save Tom wasn’t a noble gesture - her world had changed too much and she hadn’t coped very well. Tom is her only link to her own time and she thinks he’ll be able to help her. The Doctor is intrigued and decides it’s probably not a good idea to let her know the TARDIS is a time machine. But it’s too late. Charley and Kim join them and Charley reveals that she’s already suggested to Kim that it might be possible for them to take her back to her own time. The Doctor argues that it’s complicated and he has to take things like that on a case-by-case basis. In any case, Tom’s captors have already taken the TARDIS away which means the ice-cream man must have been a prison warder on patrol. It was the Doctor’s fault for alerting the guard to their presence by trying to buy an ice cream from him!

The Doctor makes sure everyone is alright. The ship appears to have crashed into one of the houses on the other side of the street. Kim identifies the ship as the one Tom crashed here in, the Led Zeppelin IV (the series of ships was named after a public vote). Kim was actually on the second Led Zeppelin mission to Phobos, before they started using cryogenics. Suddenly she sees Tom and calls out to him.

The ’ten-year old’ version of Tom is delighted to see the crashed spaceship and is baffled when Kim joins him and tries to get him to remember. She prompts him about a secret party they held on board the week before the launch, and the fact that on their journey they kept finding crisp packets everywhere. At first he dismisses the idea of female astronauts, but he slowly starts to accept that she looks familiar. The crashed ship suggests to the Doctor that Tom’s old memories still exist in his head somewhere, he just can’t access them. They decide to take him inside the crashed ship, but in order to placate the prison guards they agree to wait until Kim has sent a message from her own ship warning them what they’re going to do. C’rizz agrees to go with her while the Doctor, Charley and Tom await the arrival of the ice-cream van.

In fact, Argot and Lest have been watching their every move for some time now. They’re satisfied that the new arrivals are not part of the prison programme and recognise the Doctor’s description of his own ship as the tall blue box they collected earlier. Lest assures Argot that he’d already told him that, but his leader doesn’t remember. Perhaps he should have written that bit down…? Argot checks his notes and finds they did have that conversation and he even made a little sketch of the TARDIS to remind him. This proves they’re not part of the cellscape as Lest wouldn’t have been able to take the box outside if it was. The TARDIS can obviously move through the containment barriers somehow and one day Argot would like to take it to bits to examine it. They decide to protect their investment by bringing the captive out and performing a short-notice re-run on him, but to do that they must first sub-divide the cell in order to contain each of the new arrivals in their own bubble without any of them being aware of the others. This should have happened automatically and Lest wonders why it hasn’t already worked. Argot gives orders for the TARDIS to be moved to the vehicle hangar.

Kim and C’rizz ring on a nearby doorbell and Mrs Braudy answers. They claim to be making a television programme and ask permission to do some filming in her lounge. She lets them in and offers to make them a cup of tea. Kim comments on how rude C’rizz is to the old lady, but he reminds her that the woman isn’t real. Kim doesn’t want the guards to know she has her own ship within the cell, so they record a statement inside Mrs Braudy’s house then send it out with tracer dampeners so they don’t know where it’s coming from.

The Doctor takes Charley and Tom inside the crashed Led Zeppelin IV and they note its cramped conditions. The Doctor claims to have armchairs aboard the TARDIS, but Charley has never seen them. Tom still doesn’t recognise anything, but they make their way to the cockpit and debate the subject of speed. According to the Doctor, light-speed is a constant whereas hyper-speed varies depending on local factors, mass ratios and how recently you’ve taken your ship in for a service. Tom suddenly remembers the Marmadon smashing its way aboard, which means someone has taken the trouble to repair the damage. He starts to vomit up the substance in the air, and comments that it tastes like pineapple. He now has his memory back, although he obviously doesn’t recognise the Doctor or Charley. They hear a animal-like roar in the distance…and flee from the Marmadon which appears to still be aboard the ship! The Doctor stumbles and while Charley stops to help him, Tom races through to the hold and locks the door, trapping them on the same side as the monster. Tom goes out onto the street and meets the ice-cream man. He tells him he has to get away and Lest is surprised at how easy it was to lure Tom away from the others.

Kim and C’rizz climb up a ladder into her ship and she deliberately steps on his hand as punishment for pronouncing her name wrong on the video. They receive a message from Argot who tells them their presence in the cell is unauthorised. He adds that they’ve removed the captive as a precautionary measure and he’s currently engaged in other ‘duties‘. He warns them not to venture out of the cellscape as it’s designed to remain stable and serene and any meddling will make it dangerous.

The Doctor receives a message on his ‘mobile’ but as he’s busy trying to open the door, he instructs Charley on how to answer it. It’s Kim on the other end and Charley tells her Tom has gone and they’re currently trying to get away from the Marmadon. Kim can’t believe Tom deliberately locked them in, but she tells them what the prison governor told said in his message. Charley tells Kim and C’rizz to stay where they are, then asks the Doctor what’s shaping this place now that Tom’s been removed. He thinks it will probably stay like this until another person’s memories start influencing it. Charley volunteers to be that person - if she switches off her iPod and let herself be taken over again, everything in the cell will start to shape itself around her life instead of Tom’s.

Lest can’t remember whether he’s given Tom a sedative, but when the astronaut wakes up he realises he hadn’t. Tom remembers all this happening before, over and over again. Lest prepares to place him inside his ship as a reasonably-sized crowd is already starting to form. The leader reaches for his script to help get the crowd in the right mood while Lest goes to deal with the intruders. Argot begins his broadcast to the crowd at Falls Promenade and the audience breaks out into applause. He tells them he’s preparing to reconstruct for their viewing pleasure the first ever arrival of an alien lifeform on their world. He will be their commentator, talking them through the historic event as it unfolds before their eyes. Kim switches off her scanner after watching Argot’s introduction. She and C’rizz both agree that these people seem to be deranged!

Lady Louisa Pollard enters the drawing room looking for her husband and finds a visitor waiting for her. She offers the stranger a drink and wonders why he’s standing there with his hands over his eyes. The Doctor bursts into laughter then introduces himself. He claims this is just a social visit and apologises for his strange behaviour. Lady Louisa tells him she’s just heard the news on the wireless of the Armistice announcement, which the Doctor thinks is odd as the first British radio broadcasts were in 1920, after the Armistice was declared. Nevertheless, she’s delighted as this means her brother, a lieutenant stationed at Ypres for the last two years, will be home soon. The Doctor realises this is supposed to be 1916, which means Charley has created a composite period of time to relive her childhood but without the threat of war hanging over her. Charley enters asking her mother for some ointment after scraping her arm on a tree she was climbing. Lady Louisa rebukes her for not behaving little other little girls, but is pleased she was at least able to climb to the very top. There’s a knock at the door from the rag-and-bone man, but the Doctor recognises him as the ice-cream man. Lest also recognises the Doctor as one of the alien invaders and asks whether he’s responsible for changing the environment within the cell. The Doctor distracts Lest, then steals his horse-drawn cart, promising to return for Charley later.

C’rizz is alerted to the Doctor’s arrival over the spaceship communicator. He explains that he was able to escape from the virtual reality and has found himself in some sort of vehicle bay. The TARDIS is there, together with a dozen of the coffin-shaped escape pods from the Led Zeppelin IV. Kim and C’rizz tell him the prison governor is recreating Tom’s arrival on the planet, which suggests they need to keep Tom a prisoner in order to help them re-stage the event. They tell him it’s taking place at Falls Promenade and the Doctor decides to find the location in the TARDIS and will try get there ahead of Tom.

The commentator Argot tells the crowd that the alien spaceship is just starting to come into view now, through the lower atmosphere. Tom tries to pilot the ship away from any inhabited areas and the crowd applaud the noble instincts of a savage creature. The final descent begins and Argot warns all spectators to stand well clear of the marked area for their own safety. Argot thanks everyone for coming and leaves them all to enjoy First Contact - just as the spaceship crashes to the planet. The crowd are overjoyed! Tom emerges from the wreckage and tells the audience that he comes in peace. The Doctor suddenly arrives in the TARDIS and urges Tom to join him. Argot is delighted with the performance and contacts Lest to go and collect the captive. Unfortunately that won’t be possible as his trans-barrier transport has been stolen. Argot spots the Doctor leading Tom away to safety, but oddly the audience don’t seem to have noticed that this re-enactment was any different from normal. Lest remembers the Doctor promising to return for Charley, so at least they know where he’s going…

Inside the TARDIS the Doctor checks on Tom‘s condition and he says he feels like he’s been beaten up in an alleyway then fallen down a drain into a brutal psychedelic underworld. The Doctor knows what he means - that happened to him once! Tom apologises for leaving him and Charley at the mercy of the Marmadon, but the Doctor accepts that he wasn’t in the best frame of mind. He’s not too keen on going back to the cell and the Doctor says he can stay in the TARDIS if he wants.

The Doctor sets the TARDIS into a perfect flight pattern. The only reason it failed last time was because of the influence of Mawvik’s Doom Triangle, so he plans to spend this journey doing two things: firstly, he’s going to ignore C’rizz’s insults about his bad driving and secondly, he’s going to fix the warp ellipse cut-out. In the meantime, he wants his companions to stop bickering in front of Lest, their guest who they’re returning to his home planet. Lest is very grateful - he thought he’d never escape his life of servitude to the evil Mawvik. He’s getting hungry so the Doctor gives him directions to the TARDIS kitchens. When they’re alone, Charley and C’rizz ask the Doctor how he was able to defeat Mawvik and he explains that every time his enemy activated one of his clay minions, he was using … suddenly the Doctor is interrupted by the faint sound of an ice-cream van playing ‘Greensleeves’ in the distance. His companions didn’t hear anything so the Doctor returns to his explanation - every time his enemy activated one of his clay minions he was using a little piece of his own consciousness…

Lest parks the ice-cream van in the vehicle hangar and Argot greets him. It seems to be settling down inside the Doctor’s ship now. Argot is not so sure as he seems to remember the Doctor being with more than two people. Lest suggests removing Charley from her own bubble and placing her inside the Doctor’s one as this would reduce the demand on their processors, but the leader points out this would make it more difficult to individually remove them from their cells. They need to do this because Tom is still inside the real TARDIS and the door is locked.

Lady Louisa is irritated by Charley humming along to the music on the radio. She tells her daughter that she and her father had a chat last night about possibly taking another trip abroad, so they want to know where Charley would like to go. She wants to go to the jungles of India, or the Great Wall of China, or to see the pyramids in Egypt. She’s so excited she simply can’t decide! Suddenly the radio cuts out and the music is replaced by a recording of Charley’s earlier conversation with Kim in which she explained that the TARDIS was a time machine. Louisa believes this must be a play and she objects to her licence fee going to the author of such nonsense.

Back on her own spaceship, Kim is broadcasting the recording in an attempt to get Charley to remember who she is. C’rizz is sceptical as they already know it didn’t work in Tom’s case. He’s been able to establish that the Doctor is in another cell, although he believes himself to be aboard the TARDIS. Of the two, Charley is definitely the most likely to be distracted by an out-of-place broadcast, so they look for an alternative recording.

The Doctor completes another explanation of when he got Mawvik to activate a whole army of clay minions, and therefore weakened his psychic defences. Lest returns, but before the Doctor can ask him anything, the alien shoots him - much to the shock of the virtual reconstructions of Charley and C’rizz! The Doctor recovers outside and recognises Lest, even though he looks quite different now he’s not pretending to be human. Argot insists that he release the captive from his ship, but he claims he doesn’t know what he’s talking about.

Lady Louisa has been unable to stop the ‘science-fiction’ play so she switches the radio off, hoping that her husband can make it work properly when he returns. She notices that Charley seems a bit distracted, as if she’s just remembered she’d forgotten something. Her mother rebukes her on her poor grammar and wonders whether she herself would be more capable of educating her daughter than the school. They’re expecting her father home in time for supper, but Charley is hungry now so Louisa gives her permission to go to the kitchen and get Edith to make her a sandwich.

Inside the TARDIS, the Doctor remembers Lest again - wasn’t he supposed to be trying to get him home…? Charley calls him over to listen to the engines, which sound as if they’re going to explode. The instruments are giving odd readings and then the Cloister Bell starts ringing. Unfortunately this will delay Lest’s return home, but he doesn’t mind. They all grab onto something and then the entire ship lurches. Charley screams as she is pulled outside the ship. When a deep voices echoes around the room, the Doctor realises he hasn’t destroyed Mawvik at all, he’s simply given him access to the Vortex and he’s now more powerful than ever! At that moment C’rizz is also sucked out of the ship, leaving only the Doctor and Lest behind. Lest takes this opportunity to ask how they can open the TARDIS door, but the Doctor doesn’t understand as they’re already inside the ship. Just then, the Doctor himself is pulled into the Vortex…

As the Doctor recovers, Argot asks Lest what the experience was like, but he says it was over too quickly. Lest tells the Doctor that if he doesn’t reveal how to open the ship, the experience he’s just had will be repeated and repeated and repeated….and every time he’ll believe it was the first time. The Doctor is confident he can take the pressure but is curious why they chose that particular scenario, but they tell him they didn’t chose it - he did! The cell is programmed to create a safe place for the prisoner, all they had to do was make sure that environment was violated. The Doctor realises they are turning his own memories against him, but the two aliens don’t understand. They’ve always believed that the cell uses people’s imaginations rather than memories, because memories aren’t clear enough. The truth finally dawns on the Lucentrans - these humans are able to use their memories much better than they are.

The Doctor accuses them of treating their prisoners badly - Tom doesn’t deserve what’s happening to him, but Argot believes their captive has been happy and in addition, they’ve hugely increased his lifespan and he’s been doing the same thing over and over without even realising it. Argot and Lest demand that the Doctor hand over Tom as he’s their livelihood, and this time it’s the Doctor who finally realises the truth. People on this planet are paying to see Tom crash over and over again, because they can’t remember it sufficiently from the last time. The two warders have re-created the crash using detailed schematics drawn up shortly after it first happened. The more times they watch it, the better they can remember it. After 100 years, they’re starting to remember most of it fairly well. The Doctor wonders whether it wouldn’t just be simpler to watch it on videotape…? They suspect he’s just trying to distract them, so they drug him again and he passes out.

C’rizz tells Kim that the warders have just brought the Doctor back into his cell and they’re about to start the process all over again. However, she’s found something that disturbs her much more - a recording of a conversation C’rizz had with the Doctor earlier in which he called her judgemental and selfish. She calls him unbearable and he retorts by referring to her shrill whining! C’rizz suddenly realises that when a cell has more than one person inside, it splits off into separate bubbles tailored to the person inside and to their desires. But his mind is designed to change like a chameleon to reflect the company he keeps - if the cell tries to get inside his head it’s going to get more than it bargained for… Charley arrives in the family attic and is surprised to find C’rizz and Kim there, standing next to a spaceship! She doesn’t remember seeing them before, but she’d used to being introduced to relatives that she doesn’t know and has got into the habit of pretending to avoid embarrassment.

The Doctor wonders how many times he’s experienced the disaster inside the TARDIS, but Argot refuses to tell him as it’s more disorientating if he doesn’t know. Lest suggests the Doctor should be more worried about the strain all this is putting on his body, but he insists he’s as fit as a fiddle.

C’rizz concentrates on letting the cell get inside his head so that it can shape itself around his desires. The cell starts to act strangely as it triess to satisfy so many different desires at the same time and the wall next to him starts to bend. Charley has a coughing fit and vomits out the substance in the air, instantly regaining her memory. As the cell around them starts to melt, Lady Louisa enters and wonders why everything’s in such a mess and why her daughter is holding hands with two strangers. Has she been letting gypsies stay in the attic again? Charley apologies and tells her mother how good it was to see her again and that she hopes it won’t be so long before they meet again. The room around them, including Louisa, completely melts away, leaving C’rizz, Charley and Kim alone in an empty room, big enough to accommodate Kim’s spaceship. Charley notices the door is wide open…

Argot is getting frustrated with the Doctor, who says the experience was fun and he’d like another go. The door opens and C’rizz, Charley and Kim enter, much to the bemusement of the Lucentrans who can barely remember them. The Doctor congratulates his friends on beating the cell, then everyone faces each other and they exchanges threats and bluffs. The Doctor suggests they calm down and try to come to some sort of arrangement. For example, he thinks the aliens might be quite interested in the black box video footage Kim showed him earlier. She plays it back and Argot and Lest are amazed by the images they see on the screen. The Doctor explains the principle of a visual recording and at first they think it’s a trick. It becomes clear that despite all their advanced technology, the Lucentrans never invented video recorders. They can learn systems and technology, but they’re not very good at remembering specific events. The nano-forms know how to relay an image of something that’s happening right now, but that information is immediately lost and they have no facility for electronic storage. Kim fast-forwards to the end and they watch a recording of the moment Tom crashes onto the planet 100 years earlier. This footage was in Tom’s escape pod the whole time, but the aliens never realised its value. The Doctor admits that it’s not as spectacular as re-enacting the crash itself, but they could sell the technology and the footage. Argot is very keen - providing he’s still allowed to do his commentary.

Tom is still waiting in the TARDIS lounge when the Doctor finally returns. He’s embarrassed when the Doctor reveals he was being tortured while Tom was just sitting there reading a book all the time, but when the Doctor learns the book was “Tender is the Night” by F Scott Fitzgerald, he says he doesn’t mind. Kim greets him and is relieved to find that her old friend finally remembers her. C’rizz tells the Doctor he thinks he let the Lucentrans off a bit easily, but what was he supposed to do? He couldn’t exactly frog-march them down to the police station and in any case, revenge is a dish best left to go cold and then thrown in the kitchen bin. The technology the Doctor has given them should be enough to keep them out of trouble from now on. Charley wonders whether this was bit reckless, but it’s not as reckless as promising to take Kim and Tom back to a time when they were supposed to be dead. Which they’re also about to do…