The unnamed narrator wakes up one morning in his suburban dwelling and finds that his cat, Biggles, has suddenly discovered how to talk. Although he finds it surprising it doesn’t strike him a particularly weird. Getting the cat food out of the kitchen he sees a note he has written to himself on the fridge door, but feels no particular inclination to open it. After a short conversation about the cat’s food preferences Biggles asks the narrator for some help in locating a man called the Doctor. He says that the Doctor doesn’t live anywhere in particular, is very annoying and is known for his ability to fix things. They search together on the internet but are disturbed by a phone call from next door. Hurrying round there the narrator finds that the old lady, Mary, who is his neighbour, has discovered that her dog Sampson can talk, too.

Sampson is busy in the kitchen pulling an old radio apart to make a communication device so that he can get in touch with the Doctor.

Returning to his house the narrator notices an increasing number of cats on the window sills and in the garden of his home. Biggles tells him that he hasn’t found the Doctor yet but knows he must be about somewhere because the TARDIS is up the road. Refusing to explain what the TARDIS is, Biggles says that he needs to sort out a mess with a dimensional glitch. The narrator realises that Biggles is not his cat. Biggles agrees, complaining that body sharing with a feline is inconvenient. He says he has only been in the cat’s body for two weeks. When the narrator enquires how Biggles is aware of events from before that period, such as his name being Dolly as a kitten, he explains that he can read the narrator’s mind.

He goes on to say that he is actually a member of Species 29 and on his home planet his people have been at war for years with Species 7, and would be now if it wasn’t for the intervention of The Ageless. The narrator says that next door’s dog can talk as well and Biggles is furious, saying that Species 7 are such cheats.

The narrator returns to Mary’s house with Biggles in a rucksack to avoid the growing number of dogs outside in the street. Sampson and Biggles begin a hostile conversation about the Doctor during which they discover that each has been inside their host’s body for two weeks. The narrator is surprised to discover that he has brought the note to self with him, and a cylindrical object that he doesn’t recognise.

Sampson and Biggles recount their species’ history of mutual enmity and war. As the war threatened to destroy their entire galaxy a neighbouring race, the Ageless, had intervened, removing the warring species physical bodies. After a thousand years of peace the Ageless had appointed the Doctor as an arbitrator to see whether the species’ could be allowed to have their bodies back. Before the Doctor arrived, however, a dimensional rift opened and the species were sucked away to Earth and into the bodies of cats and dogs. The narrator asks what they want the Doctor to do for them and the cat and dog reply that they want their bodies back so that they can resume the war. If this does not happen they intend to use their psychic powers to begin their war afresh on Earth.

Outside, the cats and dogs are lining up to fight each other. Mary says that she is glad to have the narrator there with her even though she hasn’t known him long. He is surprised, saying he has lived there for years, but Mary points out that he only moved in two weeks earlier. Realising that his note to himself is now, mysteriously, in his hands, he opens it. It says You are the Doctor and he remembers that he is.

Natalie is glorying in having her body back. It has cost her 50,000 credits (three years wages) but she is now slim, toned and athletic. She looks down at the teeming city below, anticipating the glorious life ahead of her, when a heavily armed tortoise drops from the sky and fires a massive laser gun at her.

The TARDIS lands in the streets and sends a herd of beasts on the way to the market into a frenzy. Emerging into their cloud of dust the Doctor and Martha take stock of the situation and head towards the city centre. The Doctor is telling Martha that they are on Fraxinos, some 300,000 years after her time. Just then, Natalie - still in her night dress - comes sprinting towards them. She tells them that a giant, armed tortoise is trying to kill her. The Doctor guesses that it is a Chelonian. The tortoise emerges from an alley and points its blaster at them. It tells the time travellers to step out of the way because it does not want to kill the innocent, which is an improvement on their normal behaviour the Doctor notes. The Doctor uses his sonic screwdriver to freeze the Chelonian’s cybernetic enhancements long enough for them to make a run for it; unfortunately they have to go away from the TARDIS.

As they run the Doctor asks Natalie what she has done to upset the Chelonians, but she replies that she hasn’t had the chance as for the last six months she has been in the body bank. This seems to answer the Doctor’s question. As the tortoise comes back to life they jump into a flying taxi and make their escape. Unfortunately the tortoise takes off in pursuit.

Arriving five minutes later, after a hair-raising pursuit through the city, the Doctor strides into the reception of the Body Bank. Using his psychic paper he is given a guided tour as part of a ‘routine police inspection’. Colly, the owner of the Body Bank, shows them the Exercise Zone where clients regain their old bodies through a relentless exercise regime. They check their minds into the Brain and a consciousness programme is put into the body to get it fit. Colly insists that this procedure is perfectly legal on Fraxinos (but illegal elsewhere, as the Doctor points out). The Doctor accesses a news site on a screen and rewinds to film of a Chelonian Breeding Planet in the Perugorn Sector. Natalie is shown destroying the complex with a bomb and killing thousands of Chelonians. The Doctor speculates that a disembodied mind, a creature with nowhere to go, was in the body bank at the moment of Natalie’s psychic graft and sneaked into her body. It then took her to the planet and committed the crime.

The Doctor tracks down the most recent arrival at the Bank after Natalie was given her body back. It is an overweight man called Baxter. The alien mind is in residence, showing no remorse for its motiveless crime. At this moment the Chelonian bursts in demanding its revenge. It finds Natalie, stuffing éclairs into her mouth in the café. But the Doctor points out that Baxter is the culprit and explains what happened. Baxter tries to flee but dies of a heart attack, killing the alien mind. The Chelonian is eventually convinced by the explanation and leaves, satisfied.

Harry is supposed to be writing a Christmas story in his English composition class but, instead, is writing about a space war between the giant squids (the Xarantharax) and talking cows with snakes growing out of their eyes (the Iska’lanz’rm). His substitute teacher is unimpressed and confiscates his exercise book, locking it in her drawer.

Back at home, several days later, he gets up early on Christmas morning to sneak a look at his Christmas presents. Not because he is curious, more to prepare himself for the inevitable disappointment. Then he discovers an eight foot tall box inside festive wrapping paper. Opening it up he discovers a blue wooden box that feels alive to touch. Then he remembers the previous Saturday.

His mother took Harry and his younger sister to see Santa Claus at a department store. When it was Harry’s turn he was surprised that the Santa knew his name. Not only that but the man in the Santa suit seemed too young and thin and couldn’t keep his false beard in place. Instead of a typical gift, Harry was presented with a key by the Santa, who told him to use his imagination.

Remembering the key, Harry fetches it from his jacket pocket. It fits the lock on the blue box and Harry finds himself in the TARDIS. Realising that it is a time and space ship he determines to fly it, but which button to press…? Then he remembers what happened next on Saturday.

Looking for some cheap perfume to buy his mother he was served by a beautiful dark-skinned girl promoting Aroma perfume. Agreeing with Harry that it smelled pretty nasty she gave him a piece of paper instead and advised him to buy his mum a box of chocolates. Just then they were accosted by a man with a squid’s face. Harry sprayed perfume into the squid’s eyes and it fled into the crowds of shoppers.

Retrieving the paper from his satchel, Harry realises that it is instructions for flying the TARDIS. He follows the instructions and the engines start up. When they stop and the doors open Harry is looking out into space. He sees a space battle being fought and realises that it is the picture he drew to illustrate his story in his English class. The TARDIS then moves on and lands in his school corridor. He walks to his classroom and watches his exercise book being confiscated. He waits for class to finish then enters the room to get his book back. Before he can do so the teacher returns and pulls off her mask to reveal a cows’ face with snakes for eyes. She tells him he must not be allowed to finish his story. Instead of fear Harry feels anger. He pushes the Iska’lanz’rm out of the door and barricades it with the desk. Grabbing his exercise book he looks at the story and realises it is finished. He looks at the picture of the space battle what is missing. He searches for a blue crayon.

Xarantharax and Iska’lanz’rm are battering at the door. The thin Santa (now in a blue pinstriped suit) and Martha elbow their way into the room and give Harry a sonic atomizer filled with cheap perfume. Sprayed by this perfume the aliens dissolve into thin air. Harry wishes he’d imagined a better weapon.

Harry asks what has gone on and Santa tells him that there are some people with imaginations so good that they leave an imprint on the universe. He says that Martha and he couldn’t join in at the end until they had been included in the story but Harry points out that they intervened in the department store. Santa concedes that he cheated a little. When they get back to the TARDIS it is bright orange and Harry says he couldn’t find a blue crayon in time. Santa gives him a blue crayola. And the TARDIS key as a present and tells Harry he will wake up and think it was a dream.

The Doctor and Martha are having morning coffee in the Hotel Splendide and trying to look inconspicuous. The Hotel has only been open a few weeks in the resort of Bramlington-on-Sea but the TARDIS has picked up some odd readings. Just then, Lyn the chambermaid bursts into the lounge area, covered in green slime, saying that something in room 413 attacked her. It told her that everyone in the hotel was going to die before exploding into a mess of slime.

The Doctor uses his psychic paper to gain access to the room but his investigation is interrupted by the manager telling him that a guest has been attacked in the sauna. Before it died it said that it would make the other guests into zombies too. The manager, Mr. Preston, informs the Doctor that since the hotel opened there have been reports of phantom members of staff, ghostly guests and dripping slime. The Doctor heads off to the car park where the TARDIS is waiting, keen to test the slime.

The elderly receptionist confides in Martha. Her name is Margery and she worked at the Ringroad Motel in 1979 when it burned down at Hallowe’en. The Splendide has been built on the same site. She goes to ask someone to take over reception while she speaks to the Doctor but instead finds the long dead Irene Hamilton. She screams and Martha races in to find Margery slumped on the floor, covered in slime.

In the TARDIS the Doctor is looking at maps and x-rays of the hotel. He finds heaps of bodies beneath the foundations. The data bank finds the fire of 1979, too. He immediately sets off for the night in question.

In 1979 Irene Hamilton was the motel manageress. Her black sheep sister, Bunty, had recently returned to take over the kitchens. For the Hallowe’en party Bunty had prepared a spectacular, if disturbingly coloured, feast. Bunty converses with her fiancé Cecil on a futuristic communicator. Cecil is dressing for dinner when the Doctor knocks at his door and asks if he has seen any aliens about. Cecil asks how the Doctor knew and is told that his wig is not concealing his third eye. Cecil heads off to the party, regardless, with the Doctor in pursuit.

In the bar the Doctor is served some ginger pop by a younger Margery. He sniffs at the buffet and asks Bunty what she is feeding the guests and asks her why she is with a rogue Kaftakkrofakian. He warns the guests not to eat but it is already too late; guests are already turning into zombies. The Doctor bundles Margery from the room as the zombie slime works its way into the electrics causing a fire. Cecil strides after them saying that there will be no survivors to tell the tale.

The TARDIS lands on The Great Solar Shield, late in the 21st century. Orbiting the Earth it takes the heat off the planet to ease the effects of global warming. The Doctor and Martha use psychic paper to convince the crew that they have been sent from Earth as morale boosters. The crew explains that due to space radiation storms they have a life expectancy of five years; all of them expect to die on the shield. None of them were told this when they signed up, nor is there a way for them to return to Earth.

Ben is nine years old and has recently moved to the Isle of Wight where he is finding it hard to fit in with the local children. He complains of being bullied to his head teacher but as he is doing so his wristwatch flies off and smashes through her window. At the same time two men repairing electricity pylons find their truck being dragged away from them and are horrified to see the pylons heading in the same direction.

The TARDIS is above the Earth in 1973 when the controls seem to take on a life of their own. The TARDIS lands heavily on Tennyson Downs near a huge metallic structure. A mass of metal made up of anything from cars to music stands is rolling towards them. The Doctor shouts at the metal structure and, surprisingly, activity ceases. The metal ball stands silent in the distance. Martha wonders what horror and death have been caused by its journey.

The Doctor goes into the TARDIS and re-emerges with switches and levers from the console. These are pulled from his grasp and absorbed into the sides of the metal structure. It then addresses the Doctor and Martha. It tells them that it is merely feeding, but it has been careful not to kill or hurt any people because the fleshy stuff clogs its arteries. When it senses their disapproval it reminds them that they only eat things which have been alive, whether animal or plant. Then it thanks the Doctor for the snack he provided and says that should give it enough energy to move on elsewhere. The Doctor looks at the ball of metal nearby and says that it would leave a terrible mess if it was abandoned, so the creature devours it before leaving.

The TARDIS tracks a distress signal to a small spaceship which is burning up as it heads towards the planet Geravalon. Unable to help because the ship’s warp controls are taking it in and out of reality, all the Doctor can do is land before the ship crashes and wait to see what can be done.

They materialise on a muddy bank in the middle of a jungle. Two distant suns give a crimson light. Nearby stands a massive castle. A large lizard lets the Doctor stroke it and then begins to transform itself so that it looks like him. Before it completes the change the sound of the spaceship scares it into the river. There is a trail of fire across the sky and then an explosion nearby. When they reach the crash site Martha realises that there can be no survivors but the Doctor spots an escape pod lying nearby.

By the side of the pod a young woman is helping a badly bleeding man. A crowd of other people arrives from the castle and their leader, an aristocratic figure, tells them that the bleeding man is Prince Rodrique, heir to the premiership of the Majullion Confederation. The Doctor explains that he and Martha followed the ship down to give what aid they could. The man informs them that the girl was a kitchen servant, probably the only survivor of several that would have been on board. He adds that the Prince didn’t seem to mind transporting staff around. The Doctor asks the girl her name and she replies that it is Sastra but when the Doctor asks if she was going to work in the kitchens she collapses.

The man, Padros, leads the crowd back to the castle, carrying Rodrique on a stretcher among them. Martha notices several of the lizards watching them. Padros says that the Castle is the Prince’s retreat, built to the specifications of the ancient fortresses of the Hodranic Line. He says that there have been riots and unrest and the Prince is ‘giving in’ to the servile classes, giving them more rights and the power to vote. Padros says he must accept the prince’s decisions even if he does not agree with them.

In the castle the Doctor and Martha visit Sastra in her sparse quarters. She is very beautiful but lacking in confidence. She tells them that she has to go and work in the kitchens to help the preparations for the celebration to be staged the following night and they leave her.

The next day they are joined for lunch by the prince, much recovered. He talks with them about rumours that he will shortly announce his engagement to be married. He runs through a list of aristocratic candidates before declaring that he doesn’t actually like any of them and that he intends to marry for love. On a whim, Martha asks him if he is going to invite Sastra to the celebration on account of her saving his life. All of this seems news to the prince and he does agree to invite her, much to the distaste of Padros who adds that the girl will have nothing to wear.

The Doctor says he might have something in the TARDIS that will suit the occasion. When they get to Sastra’s room, however, they find the girl suffering such pain in her legs that it seems unlikely that she will be able to attend. Martha is outraged to find that servants are not entitled to medical attention. She is also surprised to find that Sastra claims to have seen the prince in the castle many times when Padros has implied that the servant is new to the place.

The Doctor finds a stunning crimson gown and a bottle of painkillers for Sastra. He tells her that the painkillers are digital and will wear off exactly on the stroke of midnight. At the ball she is in too much discomfort to do anything other than sit but she draws admiring glances from many people, not least the prince. When the prince comes to ask her to dance it is apparent that he does not recognise her. She dances with him but her agony is so great that there are tears in her eyes.

At midnight the clock strikes and Sastra stumbles from the room in pain leaving a shoe behind. Martha tries to tell the prince that Sastra hurt her legs in the crash but the Doctor says there is more to it than that. He leads Martha and Rodrique to a shadowy corridor where they find the girl lying on the floor. Her legs are green and scaly and stuck together like a forked tail. Martha realises that Sastra is a jungle lizard. The Doctor says that the lizard probably tried to help the prince by licking his wounds and infected itself with human DNA. She is dying. The Doctor says she needs more genetic material from the same source. When the prince kisses her she revives and reverts to her human form.

When Martha steps out of the TARDIS it appears that they have landed underwater at the bottom of a tropical sea. The Doctor tells her that they are in a biodome; the apex is impossibly high above them. Turning away from the ocean view they see a huge futuristic city is housed in the dome. The Doctor looks perturbed. After two hours of exploring at ground level the Doctor suggests that they go up one of the fifty storey tower blocks. By chance they notice that the lift they ride up in does not want to visit the twenty second floor. The Doctor uses his screwdriver to get off on this floor which is full of empty offices. Or rather, all are empty but one. In this room they are horrified to see a man suffocating to death while they try without success to help him.

After the man dies the door opens normally. His wallet tells them he is Leonard Farnham. The terminal he seemed to have been working on is blank. Then the words ‘Get in the lift’ appear on the screen. The Doctor and Martha head to the lift as two robots arrive to take the corpse of Farnham away. The lift takes them to an elegant chamber. A very old man sits behind a large desk and welcomes them to Subaqua One on the planet Miletus. He introduces himself as the controller of the city.

From the windows there is a spectacular view of the ocean, until the Doctor reaches over and presses a button that changes the view to London, then outer space, then a dusty wasteland traversed by storms. He declares that this is the real world outside the dome. Only the old man knows that this is the truth. Martha asks what happened and the controller tells her that there was a terrible war.

The war occurred first on the old Earth colony Sarpedon. It was a desperately overpopulated planet so the government relocated people to Miletus. No sooner had they begun transmatting than the war obliterated Sarpedon and the exterior of Miletus. The first inhabitants arrived to an illusion created by the scientists that built the dome and ever since then, for sixty eight years, the population has believed that they live under water. The illusion maintains a sense of optimism that preserves a peaceful and orderly society. Unfortunately, once in a while, someone questions the truth, someone like Farnham, and the controller kills them in cold blood.

The controller asks the Doctor what made him suspect that the ocean was an illusion. The Doctor tells him that it is impossible to terraform an Earth-like ocean so accurately on a planet half way across the galaxy. The Doctor says that the illusion is holding back the colonists. If they knew the truth they could use their resourcefulness to combat the adversities of the planet. He demands that the controller switches off the illusion for everyone like the Doctor did for the controller.

The controller refuses but a voice from behind them says that he will do it. They turn to see a young man holding a gun. The Doctor introduces him as Leonard Farnham’s son, Dan and says that he sent the lift back down to fetch him. Dan shoots the controller, rendering him unconscious. Then he tells the Doctor of his father’s suspicions and investigations. When he found out what his father was doing he came to make sure his father was alright. Now he is determined to show the true nature of the planet to the population.

It is 2025, South East London, and the Doctor and Donna are in a theme park based on the works of children’s author Aunty Winnie. The Doctor had expressed his love of the works of Beatrix Potter to Donna and she responded to her childhood delight in the stories of Aunty Winnie so he found this place for her. As they explore the Doctor is amazed at the orderly queuing and good behavior. That is, until a father sneaks a child onto a ride without paying and a giant rabbit punches him in the mouth. The Doctor steps in to help but the rabbit turns on him.

In the fairytale palace at the heart of the park the manager, Roger, bemoans this latest disaster. He is further dismayed to find that the giant bunny was immobilized by a visitor with a sonic device. He demands that Donna and the Doctor be brought to him.

The Doctor is scraping a blue jelly from the rabbit’s insides when a party of elves arrives to escort him to Roger’s office. Roger explains that the park is a living memorial to the golden childhood worlds created by Aunty Winnie. He says that he believes everyone yearns for the simpler values of childhood. He is interrupted when Donna catches sight of Mr. Tinkle ramming the park gates in his little blue car. He thunders onto the main street outside and tries to run down a jay-walker.

The Doctor, Donna and Roger set off in pursuit but Mr. Tinkle evades them. Roger lets slip that this is the latest in a line of unfortunate happenings but when the Doctor asks if it is related to the blue jelly Roger acts as if he doesn’t understand. As they return to the theme park they find that the pixies have started to slap people. Donna escorts him to the control room and asks him to switch off the magical creatures but Roger says that would leave him there alone. Since his aunty died he has had no friends in the world. Donna is amazed that he is the real nephew of Aunty Winnie and that she brought him up after his parents were killed in a freak fairground accident. Suddenly a giant teddy bear and two fairies launch an assault on the control room. Meanwhile, the Doctor has taken the blue jelly to the TARDIS for analysis. It seems to be alive. He hops the TARDIS in front of the still rampaging Mr. Tinkle and traps him in a force field. Mr. Tinkle melts into a puddle of blue jelly.

Roger tells Donna that when he was a child he was spoken to by a blue jelly. It was Borace Gamnetyaac from the Magenta Spool Galaxy and it had fallen by accident through a rent in time and space. It fed off imagination and once Roger introduced it to Aunty Winnie it helped her become the successful children’s author that everyone knew and loved.

The Doctor leaves the blue jelly in the TARDIS and races back to the theme park where the situation has deteriorated. The creatures are melting into jelly and joining up to form a larger entity. A pony in its last stages tells the Doctor that all they wanted was to create a magical and happy place like their home world but Aunty Winnie is spoiling it.

Donna is taken into the heart of the palace and finds that Aunty Winnie is still alive (albeit consisting of a few brain cells, an eye, a hand and a foot all attached to a life support machine. The hand types out words onto an old fashioned typewriter and these are instantaneously broadcast aloud. She says that Roger has prolonged her life (she is 160 years old) against her will. The Doctor bursts in pursued by the blue jelly. He says that the chaos has all been created by Aunty Winnie herself; she wanted to end the world that Roger created for her so that he would let her die.

The TARDIS lands in Coral City on the leisure planet Splendorosa. Or rather, it lands where the city ought to be but stepping out of the TARDIS doors Donna spots the city floating several hundred feet off the ground. They get a ride on a service transporter and start to explore the city, starting at Jellop’s Tourist Information Centre.

Jellop shows them round his exhibits, a few dusty suits of armour, and then gives them a brief and amateurish explanation of how Coral City suddenly launched itself into the air a few years earlier, due to the reversal in polarity of the strontilite in the soil beneath the city. When this explanation fails to convince the Doctor, Jellop refers him to Geocorp who carried out the survey. The Doctor leaves Donna testing the vibro-massage chairs in Jellop’s while he goes in search of Geocorp.

Bursting into the CEO’s office at Geocorp, the Doctor encounters Trefgar, a rather shifty man who refuses to explain his company’s findings and has security eject the Doctor. He gets back to Jellop’s just as one of the massage chairs is adopting human shape and attacking Donna. Suits of armour appear to come to life and join in the attack. The Doctor realises that the chair and armour use strontilite in their construction and uses the sonic screwdriver to boost their resonations until they shake to pieces.

Donna is given the task of getting a job in Geocorp’s offices. Once inside she finds that the company was founded one day before the city suddenly took off from the ground. Just as she relays this information to the Doctor she is apprehended by security. The Doctor races in to help but finds Donna tied to a chair. Trefgar strides in and the three of them are suddenly transported to the bridge of an alien spaceship. The Doctor recognises the pug-faced aliens as Sarriflex. He realises that the Sarriflex wanted the strontilite for their weapons in an on-going war and have decided that the easiest way to get it is to take the whole planet of Splendorosa across space to their own location. Trefgar admits that the first attempt to do this was what launched the city – a regrettable mistake – but now they are ready to steal the whole planet. While this explanation is going on the Doctor has freed Donna from her ropes and she punches Trefgar in the face. Using this diversion the Doctor teleports himself and Donna back to the planet.

When they get back they find the city has lurched over to a 45 degree angle. The plan to steal the planet is in operation. The Doctor races to Jellop’s and converts one of the massage chairs to send out a massive electromagnetic pulse and sonic blast. He takes it back to Trefgar’s office and teleports it back to the Sarriflex ship. The alien’s systems are disrupted and the ship starts to drift towards

In the Arctic Circle Professor Renfrew’s expedition has run into trouble. His young accomplices Juliet and Max are doubting the wisdom of what he is trying to achieve. They have ascertained that Spanish Flu spread this far in 1918 and are looking for the corpses of tem miners in the permafrost. So far they have only found eight but they were not deep enough to suit the professor’s purposes. The professor has taken to looking for the remaining two bodies on his own, leaving Max and Juliet at the camp. A scream takes Max out to a cave where he finds the professor lying next to a hole in the ice and, next to him, an Ice warrior.

The TARDIS lands near the camp, looking for the source of a distress signal. Juliet goes out and meets the Doctor and Donna. Max’s shouts attract their attention and they run to the cave. They see the professor’s corpse and the Ice Warrior pointing a weapon at Max. The Doctor engages the Martian in conversation and soon learns that it is Commander Issaxyr of the Imperial Bio-weaponry division. The Doctor notices the gash in Issaxyr’s side and the blood flowing out of it. The Martian refuses offers of aid and insists that the four people facing it are its prisoners.

The Doctor continues to probe for answers and the Commander tells him that after the Great War ended in 1918 the Martians decided that the time was right for an invasion. They released the flu pandemic to weaken Earth further but their ship crashed in the Arctic Circle. The local miners overwhelmed the Ice Warriors and Issaxyr was shot with a harpoon. The Doctor points out that 98 years have passed since then and their invasion was obviously cancelled, and not because a single ship crashed. Issaxyr steps aside to reveal an army of Ice Warriors in cryogenic stasis behind him. He announces that the invasion is about to begin. Unfortunately the controls that Issaxyr uses do not activate the army. The Doctor points out that the Ice Warriors were impregnated with the Spanish flu virus to make them into biological weapons. The virus has mutated and wiped out the Martians.

Donna is trying to withdraw her life savings (150 pounds) from a cash machine but finds that her money has vanished. The Doctor is apathetic about this but at last uses his screwdriver to see where the money was withdrawn. He discovers that enormous amounts of money were transferred simultaneously. This looks like alien technology at work to him but his efforts to discover more are thwarted when the cash point screen apologises that further information is not available. However, the Doctor can remember the numbers that flashed by on the screen shortly before the apology. He returns to the TARDIS with a plan.

When they dematerialize they are both surprised to find themselves on a railway station concourse. They hear a number of over-effusive apologies, about delayed trains, on the tannoy system. The Doctor thinks that the voice is mechanical but seems self-aware, technology not due on Earth for another 50 years. Looking above the concourse the Doctor spots a woman at a window; she seems to be shouting for help.

The time travellers run up to an office but can’t get in through the metallic door. A screen in the wall shows them the woman trapped on the inside. On a table by the woman they see a small grey box which is apologizing to the woman for keeping her prisoner. The woman inside explains that a year earlier she was working for the Pharos Institute, a scientific research facility. She introduces herself as Professor Sonia Blandford and her speciality is artificial intelligence. She says that she used components from a restricted file that came from an alien spacecraft, but because of professional jealousy she left the institute and took her findings with her. She created the most powerful computer on Earth and sold it to British Rail to monitor the entire rail network. Then, that very morning, the computer started to apologise. When she tried to turn it off it started to use the internet to talk to other computers and locked her in.

The Doctor uses the intercom to talk to the computer. It tells him it started robbing banks to overcome the inequality of the world. The Doctor asks to enter the office but the computer has researched him on the internet. It apologises if this upsets him but it feels he might be a threat. Seizing on the computer’s heightened sense of sorrow and injustice, Donna makes up a sob story about having her life savings stolen, a sick auntie and a missed train. The computer agrees to let her into the room.

Once inside, Donna realises that she hasn’t got a plan. Unfortunately the computer has; it intends to reduce the amount of suffering in the world by reducing the population and to that end has taken control of all the military computers. In seven minutes it will launch a series of nuclear strikes. The Doctor tries to make the computer feel guilty for what it is about to do and Donna joins in saying that if there were only two people left alive on the planet they would still manage to inconvenience each other. The computer realises the impossibility of its task and starts to feel sorry for itself and the thankless role it has been given. It tells them to take the planet and ‘shove it’ before starting to cry.

On board the Argo Jason and thirty five heroes are seeking the Golden Fleece when the TARDIs lands in the sea near the ship. It is hauled aboard in a net and the Doctor and Donna step out to introduce themselves. After a celebratory feast they all awake the next morning to the sight of land and a mass of storm clouds. As the seas rise up a wailing shriek is heard that starts to drive the crew mad. Some leap into the sea in terror. Donna suggests that they all plug their ears with cheese to block the noise. The Doctor uses his screwdriver to locate the source of the noise, declaring that it is alien. The ship is wrecked on the rocks around the land and the crew find themselves washed ashore. Donna tells Jason that they are on the Isle of Capri.

A Cyclops emerges from a forest by the beach but the Doctor points out that, strictly speaking, it is a Castelathuron from the planet Thuron. The crew pursues the alien through the forest, gradually becoming separated into smaller groups. The Doctor, Donna, Jason and the heroine Atalanta arrive at a cave. Inside they find a Sphinx (from the planet Satroz): a winged lion with a woman’s head. Before a fight can start the Sphinx is shot dead by three aliens, man-shaped apart from ugly fish heads. They say that they are Parthenope prison guards whose ship has crashed. They add that the sphinx and Cyclops escaped through a hole in the hull and now they have stunned the sphinx in order to return it to the ship. Jason points out to the Doctor that the sphinx is dead and the Doctor agrees but suggests they keep it quiet that they know.

The Parthenopes have detected the sonic screwdriver and ask the Doctor to help them repair their ship. The ship is in the middle of a clearing. The Doctor notes that it is a Castelathuron prison ship. The Cyclops launches a sudden attack on the Parthenopes and is killed, too. Examination of the ship reveals a few things: there is no hole in the hull for the prisoners to have escaped from; Atalanta wonders why the Parthenopes are using a Castelathuron prison ship; the ship is damaged beyond repair. This latter does not worry the Parthenopes – they simply demand the TARDIS as their means of escape. At a signal from the Doctor Atalanta, Jason and Donna stuff cheese into their ears as the Doctor sends out a pulse of noise like the one heard in the storm (obviously a siren to warn of escaped prisoners and warn anyone away)

In the museum housing the Bayeux Tapestry the Doctor is annoying people by going the wrong way round the display. Something is wrong with the time line and he is looking for the solution. There is no sign of Donna and the attendant is speaking Spanish. Suddenly the Doctor finds the point where everything changed.

In a school classroom Alex is learning about the Tapestry from his teacher, Mr. Peters, when a pellet is flicked at him. Alex calls out in alarm and is sent to the headmaster. On his way through the quiet corridors he is confused to see the TARDIS landing and the Doctor greet him by name. The Doctor insists that Alex joins him in the TARDIS. Inside the control room the Doctor tells Alex that there has been a divergence in the timeline and the Norman Conquest of 1066 never happened. The consequences of this include Donna Noble being wiped out of existence. Alex, he says, is the key to the problem.

They land in France, 1064 and are immediately set upon by two soldiers who capture the Doctor and are set to execute him for poaching. Alex distracts them with his mobile phone’s ringtones. At first the soldiers think it is witchcraft but when Alex reveals himself they laugh, assuming that the Doctor and Alex are travelling conjurers and suddenly become more friendly.

Two riders approach, messengers from the court of Duke William. They dismount and the Doctor addresses Alex as Turold and tells him to hold the horses. There is a bright flash and a crack so loud that the horses rear in terror. Alex holds tight to the horses and suddenly sees Donna standing on the track nearby.

Mr. Warner is a year 6 schoolteacher, watching the school Christmas show. He notices that a strange man is filming the show which contravenes school policy. He approaches the man who shows him a note, apparently from the headmaster, giving permission to film. Mr. Warner is perplexed by the note which says ‘Happy Christmas’ but when he looks again it says ‘Happy Hanukkah’.

At the end of the play the hall is emptying but the mysterious man carries on filming the stage. Mr. Warner is intrigued and strikes up a conversation. The man introduces himself as The Doctor and says that he is using the camera (with his sonic screwdriver) to look for an alien puplet from Alluren. He plays back some of his film and Mr. Warner sees a creature with black and white fur, clearly visible on the stage set in the film but invisible to the naked eye.

Three kids, Deena, Colin and Stewart, come onto the stage looking for a bag of lost clothes. Mr. Warner is surprised that they can see the alien and have called it Jess (after Postman Pat’s cat). The Doctor explains that the innocence of childhood is what lets them see the alien with their own eyes. The kids explain that they saw the creature a week earlier on the school roof and put it in the boiler room to keep warm.

They decide that the creature must like heights because they always find it high up. They need to put it somewhere safe until its parents arrive. With the school breaking up for two weeks they decide that up in one of the fluorescent light fittings is the best hiding place. They then set up a rota to come into the school to feed the puplet. Mr. Warner turns up every day for the first week of the holidays to let the children into the school. As the days pass he finds himself more and more impressed by these children. Previously he had thought of them as self-absorbed and rather stupid, but the puplet seems to have brought out a sense of resourcefulness and dedication that he hadn’t suspected.

Donna asks the Doctor to show her the Great Wall of China but when they get there the wall is still being built. They are in the Qin Dynasty, circa 200 B.C. and Donna’s attempt to take some photographs sees the time travellers arrested and carted to the court of Emperor Qin Shi Huang. The Doctor says the mystery that surrounds the Emperor is his death and overnight disappearance. When their cart arrives near the Emperor’s palace they are tipped into a pit and attacked by a ceramic robot wielding a sword. The Doctor tells Donna to use her mobile phone and the signal disrupts the robot’s, causing it to fall lifeless.

After defeating the ‘Immortal Warrior’ they are taken to the palace where they pass the Terracotta Army. The Doctor is led to the Emperor who is half human, half terra cotta. Hearing that the emperor is searching for the elixir of life, the Doctor tells him that he has the secret to immortality.

Meanwhile Donna is led away by the emperor’s advisor, Meng Tian, who transforms into a ferocious alien. He points a futuristic gun at her and claims that she has been sent by the Star Council to bring him to justice.

The Doctor finds that the emperor’s throne stands before a warp convertor. The emperor informs him that it came from Meng Tian’s celestial chariot which crashed to Earth decades earlier. Qin saved Meng Tian from the wreckage and was rewarded with the knowledge to unite China’s warring states and ascended to the position of emperor as a result. The alien also built him an indestructible body.

A total eclipse is due in six hours time, over Houston, and the Heart leaves Earth’s orbit, spreading its solar sails. The ion engines adjust their velocity and then there is an explosion in the engine room.

On board the ship there is a furious disagreement between two of the four crew members. Captain Jacobs is trying to communicate with Mission Control while Arnold is complaining bitterly about the Chinese-provided ion engines. Jacobs has sealed off the engine rooms so any repair will necessitate a space walk. Mission Control checks the diagnostics and decides a repair is possible. They also report a mass anomaly in the arms locker.

This is where the TARDIS has landed. The Doctor is busy breaking open the weapons and sniffing the powder from the bullets. He identifies the year as around 2070, the beginning of the Unified Earth. A young woman enters behind him and points a gun at him. He smiles and produces his psychic paper to identify him as working for UNIT.

Captain Jacobs and Elena make their way across the hull to the engine rooms. The Captain is desperate to meet the launch window in four hours time.

Inside the ship Danielle is leading the Doctor through the corridors. They are discussing the ships mission – twenty six light years in six hours to reach a new colony on Centauri Beta where a new Earth will be started. The Doctor is perplexed; he knows that hyperdrives won’t be developed until after the Mars and Europa colonies are established. Danielle tells him that the reason why the war ended was due to the hope afforded by the Heart and its mission, a united goal to start again. Something about the Doctor’s objections makes her think that the Doctor is not who he is saying but he deflects the conversation by asking to see the newborns that will be used to populate the planet. Danielle shows him five hundred blank embryos that will be implanted with genetic information a week after the ship arrives at its destination.

Jacobs and Elena make the repairs in the engine room. They are horrified to see that the hull is bent outwards, at the point of impact, ruling out a meteorite strike. As soon as the repairs are done the Captain begins to engage the remote ignition. Over the radio the word ‘engage’ can be heard. Unfortunately it is Arnold shouting, ‘Do not engage!’ as the Captain turns the wheel there is a flash and Elena is killed. The Captain stares in horror as the young woman’s body drops towards him and then he too is burnt away.

The ship begins to spin alarmingly. The Doctor makes it to the control room and manages to reset the orbit while Arnold tells Danielle that the Captain and Elena have been vapourised. Danielle tells him that the Doctor is from UNIT and Arnold asks him to use his authority to abort the mission. In reply, the Doctor finds a news channel on the view screens and shows them scenes of celebration on Earth. He says that the fact that there is only good news on Earth is bad news for the mission.

He goes on to expound on the ship’s impracticality. Taken individually each component looks perfect but anyone with a complete overview it soon becomes apparent that the mission is doomed to fail: the embryos are too old for genetic implants to have any effect; there are too many of them for such a small crew to look after. In response to this, Arnold points his gun at the Doctor.

He says he has known all along that the so-called hyper drive engines are nothing more than a large bomb. When it explodes the people of Earth will think it has jumped into another part of the galaxy. It will be thirty years before anyone realises the truth and by then a unified Earth won’t even care.

When radio contact is re-established with Houston, Danni tries to tell them that Captain Jacobs is dead and that the mission is a fake. The controller ignores her, feigning an ongoing communication problem, and gives an emotional and pre-planned speech about the new hope that the mission is giving to Earth. Meanwhile, in the engine room, the Doctor is trying to persuade Arnold to leave the ship with him and Danni in the TARDIS. Arnold refuses because the ship is pointing in the wrong direction; if it ‘launches‘ while facing the wrong way everyone on Earth will know that the mission failed and the violence will resume.

Suddenly, the hyperdrive coil begins to rotate. Arnold orders the Doctor to return to the cockpit and programme the coordinates while he stays in the engine room to complete the repairs. The Doctor tries to argue but Arnold uses his gun to drive the Doctor out. Arnold clearly wants the Doctor and Danni to escape before the explosion. Reluctantly, the Doctor departs.

The Heart rounds the moon and engages hyperdrive in a cascade of light. The watching people on Earth cheer as a chain of explosions shimmer along the hull and then the ship is gone. In Houston the celebrations begin but the controller announces his retirement and calls his wife.

When the Doctor arrives in a small English town in the early twenty-first century he is perplexed to see a bright green cat. Following the sounds of laughter and excitement he reaches the high street and sees a beautiful rainbow that comes to Earth just outside a greengrocer’s shop. A crowd of laughing people is looking at the fruit displayed outside the shop; they have become vividly exotic in colour and not at all the colours one might expect. As the crowd jostles closer the greengrocer tries to fend people away from the rainbow but an old woman is pushed into the light. As the Doctor forces his way through the crowd he sees the woman’s hands turn violet. The shopkeeper asks the Doctor to lead her into the shop’s interior where he finds a bright yellow man, two green schoolgirls and a variety of other people in assorted vivid shades.

They tell the Doctor that the rainbow arrived ten minutes earlier. When each one touched it they felt it was more than light, describing it variously as ‘solid’, ‘fizzy’ or ‘fuzzy’. Everybody then turned the same colour as the first stripe of the rainbow that they touched. Just then the old lady and a violet policeman collapse unconscious. The Doctor ascertains that they are still alive when a noise from outside attracts his attention. The base of the rainbow is spreading in pools across the pavement and s it catches the feet of the now-fleeing crowd they begin to soak up the colours. The red pool spreads into the shop but has no effect on the yellow man as it passes under his feet. Nevertheless, the Doctor starts to drag the unconscious policeman away from the pool when the officer suddenly vanishes.

The people in the shop back away into a storeroom to avoid the pool and as they do so the indigo people fall unconscious and the violet old lady vanishes. The Doctor climbs up some shelves to get away from the spreading pool, announcing that he intends to sort things out. One of the schoolgirls helpfully points out that the people passing out are doing so in the reverse order of the rainbow. The Doctor times the incidents that follow. Ten seconds after the indigo people vanish the blue people collapse. He reckons it took ten minutes between the people collapsing and their disappearing. Jumping into the red pool, which by his logic should make him the last to go, he reckons he has half an hour to solve the mystery.

He runs out into the street and starts to climb the arc of the rainbow (spotting his green TARDIS far below). When he reaches the highest point he slides down the rainbow through the roof of a high-rise building, then through the attic and a series of bathrooms until he lands in a beige bedroom where a girl is screaming at his sudden arrival.

While the girl clams down the Doctor notices that the rainbow is emanating from a cracked rock perched on a table. Various objects in the room are unnaturally coloured in bright shades. The girl introduces herself as Bobby and assumes from the Doctor’s bright red colour that the rock is his. When he denies this she tells him that she found it in the park. When she picked it up it shot out a blue beam and turned a daffodil blue. By pressing other parts of the rock she found that it sent out other colours. She took it home and tested it on other things around her room. Her intention was to use it to change the colour of her red hair – the Doctor interjects that he always wanted to be ginger – but before she could do so she noticed that the rock was cracked. The crack widened and a rainbow shot out through the ceiling.

The Doctor tells her that the rock is a device used by a race called the Filbiks to help them classify and collect things. They colour code different objects according to type, then a sedative kicks in before the animal or object is transported to their ship. The Doctor uses his sonic screwdriver to close the crack in the rock before realising with alarm that his time is almost up. He tells Bobby that it is up to her to contact the Filbiks and explain what has been happening and then he promptly passes out.

Dennis Bridger wakes up in a hotel in Cheltenham with all the symptoms of a hangover, except, unusually for him, he had not been drinking the night before. He is the resident psychic on a television show where the team tries to track down ghosts in supposedly haunted locations. For years he has feigned being possessed, basing his performances on information secretly slipped to him by his assistant, Tonya. However, he has recently started to experience disturbing dreams of a yawning chasm and voices and is beginning to wonder if he truly has supernatural abilities. As he dresses he remembers, with horror, that the reason why he is in Cheltenham is because tonight is the live show from Ratchett Abbey.

Corynne Fletcher, the presenter of Scared Stiff for the last five years, breaks off from briefing witnesses to the ghostly happenings at the Abbey. She talks to one of the crew, Simon, about Dennis’s drinking. This is not her biggest worry. There is a new threat to the show’s popularity: a man called Preston Gilchrist.

Gilchrist is a plump, rather old fashioned man with a gift for magic tricks and an encyclopedic knowledge of spiritualism. After amusing Tonya with some card tricks he feigns a ‘possession’ and tells her some messages from her deceased Uncle George. After he laughingly reveals the ease with which he performed the cold reading Tonya begs him not to show Dennis up again as he did on the previous show. Gilchrist merely shrugs.

In the Abbey crypt a skeleton emitting a blue glow shuffles up some steps. After it has gone, the TARDIS materialises.

As the audience of three hundred people settles into their seats in the Abbey, Corynne reflects on the positives for the show. It is a cold Halloween night and there have been many sightings of skeletons in the Abbey. Even Dennis seems steeled to fight off Gilchrist’s on-air skepticism. While the threat of the show being cancelled after five years still hangs in the air she is confident that a good performance tonight will see their contract renewed.

Gilchrist saunters through the corridors of the Abbey. He is planning beyond this evening’s humiliation of Dennis to the show of his own that will inevitably transpire. As he whistles the opening bars of a tune he is composing for his show a skeletal hand reaches out and snaps his neck.

As a consequence, when the show gets under way, Gilchrist does not make his dramatic entrance through the arch in the Abbey. Corynne is left floundering for a few seconds until ‘Doctor John Smith’ emerges in his place and announces that the show needs to be stopped.

The blue skeleton stands next to Gilchrist’s body. Blue smoke wreathes from its mouth into the corpse which stands up and sets out in search of friends. Opening up the tombs in the crypt he calls to his brothers and sisters.

The Doctor tells Corynne that Gilchrist has been delayed and he is filling in. a voice in her earpiece tells Corynne to go with it. She explains the various visions that have been seen recently and while a video is being shown of some recent sightings the Doctor takes the opportunity to say that this is a weak point in space and time and that something is forcing its way through. After a cut to the adverts the Doctor demands that the show be stopped and relates how he found Gilchrist’s body. As he does so he is distracted by a monitor showing one of the Abbey’s rooms. A blue, ghostly figure is swirling in the darkness, groaning ‘Pity the Gelth.’ The Doctor says he detected a tiny rift into another dimension and that the Gelth are trying to get through before it closes.

His explanation is cut short by the arrival on set of Dennis Bridger, Gilchrist’s corpse and six skeletons containing blue lights in their ribcages. The Doctor again demands that the show is taken off the air just as they are told that it is going live again, but Corynne refuses. This is too big a scoop to pass over.

Dennis is overwhelmingly pleased that he truly has a psychic gift. He can hear the Gelth speaking through him. The Doctor recognises what is happening – Dennis is keeping the rift open with his abilities – and tries to distract him. He pretends that Dennis has been ‘Freaked Out’ by a rival show as part of a Halloween spoof. Corynne joins in, adding that Freaked Out is a new ITV3 show. As doubt sets in Dennis loses control of his powers and the skeletons collapse to the floor. Gilchrist’s corpse falls, too, and the blue ghosts depart.

One wet Wednesday afternoon, on the colony world of Lindis, marauding space Vikings load ‘suitable subjects’ into the hold and set sail in flying longships for Asgard. Among the subjects is the Doctor. He has got himself captured, deliberately, along with a villager, Bjorn. Bjorn has told him that the Space Vikings only kidnap men and have been doing so for four years. A month earlier, Bjorn’s brother Sven was taken.

When the ships land the Doctor and Bjorn hide until the prisoners are unloaded. As they sneak off the ship, the Doctor is puzzled to see they are in Valhalla, at the Halls of Asgard, and wonders why somebody is recreating Norse myth. Bjorn spots his brother, dressed as a Viking. The Doctor mentions that the real Vikings did not have horns on their helmets, so the headgear of the Space Vikings must contain mind-control antennae. Bjorn rips off his brother’s helmet, killing him instantly, but the Doctor adds that his mind had been overwritten by implants and he would never have become his true self.

Sixteen year old Harvey wakes up lying on a floor but with no memory. He also has the Doctor kneeling on his chest and shining a blue light into his eyes. After some gentle reminding on the Doctor’s part, Harvey remembers that it is three days after Skylab crashed to Earth and that aliens have invaded. The Doctor tells him that they are on a train heading for Sydney.

Harvey lives on a farm near Esperance, Western Australia. The Doctor reminds him of events of a few days earlier…

Harvey, an only child whose mother has died, helps out on his father’s farm. Harvey spends a lot of time stargazing and is particularly excited when he hears that Skylab may fall on Western Australia. On the night in question a huge fireball streaks over the house and small, hot objects fall onto the roof. Harvey’s dad decides that whatever fell might be worth some salvage money and they set off into the bush.

They park the ute and find two metallic cylinders, one of which is open at one end. They are distracted from their search by the sudden arrival of a ferocious, blank-eyed kangaroo and then by the Doctor. Harvey tries to warn off the Doctor, saying the cylinders belong to him. It is then that his dad arrives from the bush, wearing sunglasses despite the darkness, and loads the cylinders into the ute and drives off, barely giving Harvey time to scramble aboard.

After a night of dreaming about men in brown suits and zombie kangaroos, Harvey wakes to find his dad still wearing his sunglasses and an item on the news offering twenty thousand dollars to the finders of any Skylab wreckage. Harvey suggests that they take the cylinders to Sydney to claim the reward but his dad tells him to be quiet. Then Harvey sees the Doctor poking about in the yard.

Harvey checks the barn and finds the two cylinders, still warm, on the workbench. He wonders how his dad didn’t burn himself carrying them the night before. His dad arrives and tells him to leave them alone, knocking Harvey to the floor in the process. The Doctor appears and points his screwdriver at Harvey’s dad. It causes a green gas to pour from his head and the Doctor uses the screwdriver to open the intact cylinder and the gas floods in. the Doctor mentions something about Zalphons, incomprehensible to Harvey. He goes on to explain that something crashed into Skylab the night before as it fell from the sky. He was parked in orbit and saw the whole thing. The cylinders are Zalphon escape pods and there was one Zalphon in each (though there are now two in the single intact cylinder). Zalphons are parasitic mind-skippers, he adds. Just then, a car pulls up and three men in sunglasses get out. The Doctor says they are a Zalphon recovery team and barricades the door. Harvey, still disbelieving, forces a loose plank away from the back of the barn and grabs the cylinders. He runs off with them, out into the bush.

Back on the train, Harvey remembers that he made it to Perth and stowed away on the Indian Pacific for a three day journey to Sydney. On the third day the train hit some cattle on the track and the cylinder falls to the floor. Gas escapes and Harvey is possessed. Fortunately, the Doctor was on hand to save him. This explains how he came to wake up on the floor of the train with a hole in his memory.

Once in Sydney, Harvey is surprised when the Doctor says they should go to the Morning Globe to collect their reward. A van roars up and two men bundle them inside. One of them is Wade Johnson, editor of the Morning Globe. He thanks them for retrieving his two Zalphon colleagues. He tells them that there was an accident on board the Skylab, which the Zalphons were using to locate every human on Earth so that they could more easily infect them with Zalphons stored aboard the mother ship.

They are taken to a chamber in a huge building. It is full of green, glowing containers. As the cylinder is opened to let the Zalphons infect the Doctor and Harvey the young boy hears the sonic screwdriver. Their captives clutch their heads as the gas escapes and the Doctor tells Harvey to get the two men into a lift. Giant rockets ignite deep below them, but the Doctor adjusts a control panel. He tells Harvey he is sending the mother ship to the Antarctic where it is too cold for the Zalphons to survive.

Rosie creeps into her sister Lola’s bed, terrified that the man in the chair is back. Lola sighs as she cuddles her sister. She warns her not to wake the others in the dormitory. A pile of girls’ dresses on the chair vaguely resemble the figure of a man. Lola promises Rosie that monsters aren’t real just as the shape on the chair comes to life. It lurches to their bed, sniffs and Rosie screams. The two girls dash to the locked door. The monster wrenches Rosie away and starts to swallow her. The Doctor arrives, as if from nowhere, and helps Lola pull Rosie back out but the door opens, throwing them off balance and the monster swallows Rosie whole.

Mrs. Hatchet surveys the scene, a pile of dresses fluttering to the floor, demanding to know who the Doctor is. He gives his name as Doctor John Smith, and produces his psychic paper, showing that he is an inspector from the Crabtree Trust, deciding whether to make a grant available. Mrs. Hatchet becomes very welcoming at the mention of money and allows him to examine everything.

Lola accompanies him on his search. She explains that her parents were explorers, lost at sea on their way home from Egypt. The Doctor promises to find Rosie for her.

Agatha, the kitchen maid, says that lots of girls have disappeared over the years. She says she can hear them in the walls, crying. She also says that staff members are always leaving because of things moving that ought not. One girl lost two fingers in a mangle. She says she was born there and is scared of the outside world. If she wasn’t so scared she would leave, too. The Doctor hands his stethoscope to Lola and tells her to listen to the walls. Faintly, she hears the distant crying of girls. Rosie’s voice, louder than the others, calls for Lola.

At that moment the furnace arrives from the cellar, its grating like a blazing mouth, and gobbles down Agatha. The Doctor puts it out by using a washing line to lasso a pan of gruel and dump it on the furnace. (He claims to have been Kansas Rodeo Champion three years running: 1804, 1840 and 1859).as they go down to the cellar the Doctor notices a green crystal in the brickwork. Before he can remember where he saw it before Rosie’s voice calls out. Lola runs towards it into an open doorway. The door slams behind her.

By the time the Doctor gets there the door has gone and he hits a blank wall. He stretches his arms along the wall and realises with horror that he can feel the walls on either side. They are closing in on him. Despite his best efforts they close around him until he is being crushed in a tiny space. Despair fills him and as it does the crystal in the wall glows brightly. He remembers where he has seen it before and what he must do.

Lola, too, is trapped in a dark space and something is slithering towards her. Before she can scream the bricks part, the Doctor reaches in and pulls her to safety. He hurries through the corridors of the orphanage, explaining that the crystal was used by Lucidians to power their stardrives. It fed on their desire to explore and carried them across the galaxy. He guesses that a Lucidian ship crashed or landed on Earth and that the stone for the orphanage was quarried from the crash site. Now it magnifies the emotions of everyone in the orphanage.

The Doctor finds Mrs. Hatchet, drunk, in her parlour. He tells her that the grant has been refused because of the terrible atmosphere in the orphanage. He says her unhappiness scares the children; they become withdrawn which she takes as ungratefulness, this makes her angry and the vicious circle goes on. She shouts that it was the children that drove her husband to an early grave; he built the orphanage from nothing. As she rails against him the walls around her glow a vivid green. The Doctor points out that her husband must have loved the children, but she screams at him for mentioning her husband. The emotional impact blasts the Doctor backwards, knocking him out. Lola flings her arms round the woman, saying she knows how it feels to be alone. As it dawns on Mrs. Hatchet that the girl is telling the truth she starts to feel less alone and a white light bathes the room. The walls become insubstantial and the missing children climb down from them. Rosie jumps into her sister’s arms from a painting above the mantelpiece.

Mary and Tommy make their way home from the music hall. They stop off for a quick drink in the pub, and then Tommy takes Mary through a gap in a fence so that they can share a moment of passion in a junkyard. The yard is full of hundreds of doors and Tommy leans back against one. It opens and he falls into the void beyond. As it slams shut again Mary scrambles through the fence into the alley just as the TARDIS materialises in front of her. As the Doctor steps out she flees for her life, back to 256 Beaton Square and in at the servants’ entrance. Scoggins, the butler, is set to scold her but she collapses and he reaches out to catch her.

The Doctor strides around the junkyard. He knows that alien interlopers are about (for one the TARDIS detected them, for another he can hear them squeaking). He walks down the bank of the Thames to lure them out. After a while, and still unaccosted, he turns back. Passing under an archway he sees an ornate door. He peers through the letterbox and sees a swirling pink vortex. A second door on castors is trundling towards him. Delighted, the Doctor heads towards it but it turns and speeds off. He returns to the first door but it, too, has gone.

256 Beaton Square is the residence of the Home Secretary, Jeffrey Fairbairn. The house is in uproar as a dinner has been arranged at short notice for important diplomatic visitors.

The Doctor returns to the junkyard. A shabby green door approaches him. It tells him that it alone of its race has mastered human language and that many of its brothers are hibernating after a long journey. It tells him that it has spoken to the Prime Minister and arranged a dinner for that evening. The Doctor asks if the door has a name and when it replies in the negative he calls it John Henry after the inventor of the doorbell. The door has no idea what a doorbell is so the Doctor offers to find him one. John Henry asks for the Doctor’s help brokering a lasting peace between Britain and the alien doors. Their conversation is cut off by a scream. The Doctor turns to find they are being watched by a very pretty girl in a maid’s uniform; Mary has returned to the place where Tommy vanished. John Henry is perplexed, wondering how a young man could have gone through one of the doors. He asks the Doctor to accompany the door delegation to the dinner that night.

Naturally, the Doctor is delighted to find himself among the extravagantly dressed humans. When a furniture van turns up outside and the doors wheel themselves into the house on Beaton Square the delegates are too polite to mention that they are doors. John Henry translates their knockings and flapping as flattery about the city. The Doctor can see a greedy glint in the Prime Minister’s eye as the leader speculates on ways to exploit the alien visitors.

A junior minister excuses himself and leaves the room. He is followed by a door and, in turn, by the Doctor. The Doctor sees the young man making a phone call, oblivious to the approaching door which swallows him up. Then it turns to face the Doctor. The Doctor races back to the dining room and demands to know what the aliens are playing at. He warns the Prime Minister that an invasion is under way. The ministers chuckle until their leader is swallowed up. John Henry translates a message, saying that the cabinet will be dispatched before breaking down into a wail of disbelief at the way he has been betrayed.

John Henry storms out, followed by the Doctor. He grabs Mary by the hand and takes her out to the furniture van where the disconsolate translator is waiting. He claims that he was an innocent party and the Doctor expresses his belief. The Doctor takes the van and heads back to the TARDIS to keep his door friend safe. As they set off the other doors come after them. They take off and fly after the horse-drawn van. As they tear through the streets the Doctor says that the doors are planning to take over the world by swallowing the leaders and then, probably, the rest of the population. Doors descend on the van and swallow the horses. The van careers to a halt and is immediately surrounded. The Doctor warns them that if they return the missing people he will forgive them, but if not…

The doors close in. the Doctor rings John Henry’s bell and raises his sonic screwdriver. The sound is magnified immensely. After it fades the doors stand in silence, deafened. With no communication they are thwarted. He knocks on the leader. It collapses, followed by the others. The Doctor opens a door and there is no alien dimension beyond.

The Doctor is piloting the TARDIS alone, talking to himself. On a screen he sees temporal fluctuations, spatial drift and timelines going in the wrong direction. Somebody is messing with time. He lands the TARDIS and steps into a modern Earth city. He is in the east of England, 2180 and has no idea what the city is. A passing old man tells him it is Haldenmor. Screams from a nearby building alert the Doctor and he runs into the reception area of a skyscraper. A security guard, female and pretty, asks him to wait outside. Instead he shows her his psychic paper and asks her name. She is Carla and she thinks he is a building inspector. She tells him that the fire alarms have sounded on the third floor and people say they have seen ghosts coming out of the walls. Together they enter the lift while Carla tells him that the building is full of accountancy offices. They exit the lift into a large, open-plan office. One of the walls in front of them shimmers and becomes an earthen wall with a flaming torch. The carpet becomes sawdust. A spark from the torch sets fire to a piece of paper. Carla looks at it in puzzlement and twenty men dressed as Viking warriors appear out of thin air. They walk across the sawdust but vanish again when they meet the modern carpet. The earthen wall shimmers and returns to normal.

Carla accuses the Doctor of lying about his identity; his lack of fear gave him away. He points out that Carla didn’t exactly run away but she shows him her gun. He introduces himself as the Doctor and says he can sort out the problem.

They run down the street, following a signal. A shop turns into a mud shack and more Vikings appear intent on attacking the startled shoppers. Carla distracts them by offering to fight them all. Suddenly, the Doctor and Carla are being chased through the now-deserted shopping mall. They divert into a sports shop and arm themselves with protective cricket gear and bats, then charge at the warriors. Carla drives back the warriors with a variety of martial arts moves until they suddenly shimmer and vanish. The Doctor leads her off now to the nearest library.

He looks up the history of Viking Haldenmor and finds that the settlers in the region in 900 claim to have won their land by fighting off demons from stone towers. Carla recognises the description as being her city in 2180: they are seeing the Vikings as ghosts but the same is true for the Vikings. The Doctor is alarmed by the book’s story of Viking victory in a major battle – a lot of people are going to be killed. He says he needs to find out what is causing the problem and Carla suggests they try the Theoretical Physics Research and Development Centre a few streets away. On their way they see a Viking long ship tumble from a nearby building and vanish before it hits the road.

At the research centre his psychic paper introduces the Doctor as a surprise inspector. The manager, Jerry Monroe, asks what he is there to inspect and is taken aback when the Doctor mentions time travel. He is taken to a room where a blackboard full of equations shows him that the researchers have made a clumsy but palpable breakthrough. Unfortunately, he tells Monroe, their experiments over the next few years will cause ripples in space time leading to the Viking apparitions. He orders Monroe to stop the research. When the manager goes to check the Doctor’s credentials Carla is amazed to see her new friend wiping the equations from the board and erasing all the computer files with his screwdriver.

Carla realises that the Vikings will never fight their battle, never gain the dominance the victory earned them and therefore never found her city. Her life is going to vanish. The Doctor tells her not to worry; she will be born elsewhere into a different life. He says he already knows that she will be fantastic at whatever she ends up doing. She says she has enjoyed meeting him and wishes they could have been friends. She asks him to look her up in her other life; if she is never born she asks him to remember her. The Doctor presses the erase key on the computer and finds himself in a field with the TARDIS a few hundred yards away.