In the Valley of the Kings in Egypt, archaeologist Howard Carter oversees the excavation of a previously undisturbed tomb. He believes it belongs to an overseer of the Fields of Amun and is sure it’ll contain many interesting artefacts, possibly even a mummy or two. As his team pull on a rope attached to the huge boulder that’s blocking the entrance, Carter’s assistant Jane Templeton urges the young student Robert Charles to put more effort into it. Robert hopes the tomb isn’t cursed, but Carter rebukes him and says there’s no such thing. Eventually the boulder breaks up and crumbles, showering the group in dust. Carter checks that everyone’s alright, but Robert is disturbed by a strange sensation which felt like someone had just walked over his grave. Carter reminds him the tomb has been sealed for 3,000 years and thinks it was just a minor earth tremor caused by the displacement of ancient air. The three archaeologists collect their lanterns and prepare to see what’s inside.

In the TARDIS, the Doctor, Ace and Hex are buffeted around the control room as the ship passes through a spot of time disruption and is literally wrenched out of the Vortex. The Doctor attempts a rather tricky manoeuvre and ends up with singed fingertips. He directs Ace to hit one of the buttons and before long the TARDIS returns to normal…but Hex is disturbed by a strange sensation and hears a voice whispering the words “remember Thoth”. The Doctor says it’s probably just a residual time echo conveyed through the TARDIS’s telepathic circuits. He discovers they’ve landed in Thebes in Egypt in the year 1902, so they decide to find out if this is where the time disruption came from.

At the excavation site, Robert is frustrated by delays caused by the collapsed roof and flood damage, but Carter tells him he must learn to be patient. Jane rushes over to them excitedly and shows them a miraculously preserved artefact. It’s a small wooden box, covered with hieroglyphics and containing what Robert thinks are ’toy soldiers’. Jane tells him they’re shabti figures, placed there to act as servants in the afterlife. The number of figures a person had was based on their status and the Egyptian Kings had hundreds of them, but this box contains only 45. Jane takes the box to the supply tent where they’re keeping all the other artefacts.

Carter is furious to see the Doctor, Ace and Hex arrive at the scene and he tells them the area is out of bound to sight-seers and civilians. The Doctor agrees whole heartedly and when Carter demands to see copies of their authorisation, he points out that Carter himself, as the Chief Inspector of Antiquities, is the right man to grant such authorisation. The Doctor claims to be a colleague of Professor Petrie from University College and introduces Ace and Hex as his students, then he deflects any further unwanted questions by sending Ace and Robert to make some tea for everyone. The Doctor deduces that they’re on the far side of the East Valley, which makes this site KV 45 (although he has to quickly stop himself when he realises Carter hasn’t called it that yet). After Carter agrees to take them on a guided tour of the dig, Hex confirms with the Doctor that this is the man who in 20 years time will discover Tutankhamun's tomb. The Doctor suspects Hex might be particularly sensitive to the effects of whatever latched onto them in the TARDIS, so he asks him to keep his senses attuned for anything unusual.

In the kitchen tent, Robert warns Ace that the tea here is rather noxious. She asks him about the tomb and learns that it belongs to Userhat, a servant of Amun, one of the principle Egyptian Gods known as the Hidden One. Jane joins them and adds that Amun’s true identity and appearance could never be revealed, but he was able to resurrect himself by shedding his skin. Ace says that reminds her of a friend of hers, which Jane finds curious. When she learns about the Doctor, she doesn’t seem to share Robert’s enthusiasm for having another archaeologist around.

As they explore the tomb, Hex admits that he’s a bit creeped out by all the mummies. The Doctor assures him they can’t hurt them, but Hex can’t forget that the husks were people once and he says it’s really weird to think they could pop back in the TARDIS and see their Christening, wedding and funeral all on the same day. They catch up with Carter and Hex hears faint voices, but when he mentions it to the others he discovers no one else heard anything.

Robert goes to the supply tent to collect sugar for the tea. He thinks he can see some of the workmen inside the tent, but as he pulls back the flaps he discovers there’s no one there. He calls out a warning in case there are intruders hiding somewhere, but then he starts to hear faint voices in the air. Then he screams in absolute agony…

Ace thinks she heard something, but when she asks Jane to listen, there’s only total silence. In fact, all the noise outside the tent has stopped and Jane is angry to think the workmen have downed their tools again. They open up the flaps, but the landscape has totally changed and the dig has completely disappeared, leaving nothing but sand for miles around. Ace goes out to explore, but she immediately cries out in pain and races back inside the tent. Incredibly, the sun has burned her hands so much they’re blistering. Jane tries to ease her pain with a wet cloth and when Ace tells her the sun was an angry red colour, Jane realises there must be something wrong with the ozone layer. They smell burning and discover the tent itself is catching fire. Ace tells Jane they’ve been projected forward in time to a point where there’s no escape from the sun’s radiation. They cover themselves with blankets and prepare to race towards the site of the dig, praying that even this far in the future, the tomb won’t have been filled in.

Carter takes the Doctor and Hex to the supply tent to show them the shabti box, but when they go inside they discover a body. Hex says the man’s been dead for years, possibly even centuries, but Carter recognises the clothes and identifies it as Robert Charles. The Doctor realises he must have been caught on the outside edge of a localised time field, but when he tracks down the epicentre, he discovers the kitchen tent that used to be on that spot has disappeared - along with Ace! Hex says someone has taken the figures out of the shabti box and when he counts them, there are only 44 left. Carter is furious and becomes suspicious of the Doctor, accusing him of vandalism and demanding once again to see his credentials. The Doctor reveals that he’s a Time Lord and says he came here on the trail of a disturbance in space-time. He wonders what’s happened to the missing shabti figure…

Ace and Jane race towards the tomb entrance and are relieved to discover it’s still there. They reach the shelter of the entrance just as the blankets they were using to cover their heads catch fire, but to their horror they discover the gates are locked and they can’t get in. The sun is still rising and they won’t be shielded for long, but there’s nowhere else they can go. Suddenly a huge robot appears and confronts them, claiming their presence here is unauthorised. Ace identifies the robot as a security droid, but it orders her not to speak unless asked a direct question. It says it has the power to neutralise them unless they comply with its orders and it demonstrates its power by shooting at some nearby rocks.

Carter is worried about what he’s going to tell Robert’s father, but Hex points out that they’ll probably be next unless they can work out what’s causing the time disruption. The Doctor asks Carter to translate the hieroglyphics on the box and he says it tells the story of Geb (the sky) and Nut (the earth), who argued with Ra (the sun) and unbalanced the world’s orbit. Ra was tricked into changing his position in the sky by Thoth (the diva of time and magic), which altered the angle of the Earth in relation to the sun. Carter notes that ancient calendars do indeed show the sun rising and setting in a different place. The Doctor realises the myth relates to a shift in the Earth’s axial rotation, but he’s not sure yet what it all means. They’re interrupted by a commotion from outside and when they go to investigate they’re confronted by a huge creature, like a cross between a hyena and a bear. They watch as the monster attacks and kills some of the Egyptian workers, then it sees the Doctor’s group and heads towards them. The Doctor identifies it as a creodont, the largest mammalian predator ever to walk on this planet - and it’s been extinct for 20 million years!

In the far future, the robot discovers Ace and Jane have not been equipped with authorisation chips. Although Ace claims they’re just tourists, it believes they must be heritage raiders and says they must be subject to the ultimate jurisdiction. As it prepared to neutralise them, Jane says she has something in her satchel that will prove their credentials. She produces a key and the missing shabti figure, but the robot is even more convinced they’re heritage raiders and it opens fire on them. Jane drops the two items as they both dive for cover, then she calls out to Ace and tells her to place the key inside the shabti figure’s mouth. As she does so, Ace is amazed to hear the sound of the TARDIS’s engines. She’s even more surprised when Jane reveals that this isn’t the Doctor’s TARDIS, but her own. She opens the door and they race inside as the robot opens fire on them again…

The Doctor leads Carter and Hex back inside the tomb, confident the creodont will be too large to get through the door. Unfortunately the stones are old and brittle and the creature’s attacks are causing the doorway to crumble around them. The Doctor promises Hex he’ll think of something, but he’ll have to be quick as the creodont is close to breaking through…

Inside the other TARDIS, it’s Jane’s turn to be surprised when she discovers Ace is also a time traveller. As Jane sets the controls, she reveals to Ace that she’s a trainee Time Lord, although she suspects she’s missed her graduation day by now.

To Carter’s horror, Hex starts to throw various priceless artefacts at the creodont in an attempt to deter it. It has little effect and the Doctor says they have no choice but to go deeper into the tomb and squeeze themselves into the smallest spaces they can find. Carter points out that the creature will still get them eventually, but the Doctor says the temporal field is unstable and the creodont could vanish just as suddenly as it appeared. Then, as the creature is about the break through, they hear the sound of the TARDIS engines and a police box materialises in front of them. Hex is impressed, but the Doctor admits it has nothing to do with him. The door opens to reveal Ace and the Doctor congratulates her on her timely intervention. They decide to leave the explanations until they’re all safely inside.

Bringing an incredulous Carter with them, the Doctor and Hex join Ace and Jane inside the TARDIS and close the doors, then they watch on the scanner as the creodont fades from view, just as the Doctor said it would. Hex asks the women how they managed to pilot the ship, but Ace tells him this isn’t their TARDIS, but Jane’s. It looks identical to the Doctor’s ship because it time-linked itself to his TARDIS in order to stay alive. The Doctor knows this ship is dying, but he says it should have been put to sleep long ago as it sounds like it‘s been suffering for centuries. He believes it’s become dangerous and is beyond repair, but Jane tells him it’s the only way she can get home.

Jane reveals that she’s a student from Year 45 and she came to Earth centuries ago on a field trip during Academy History Module 101 to study Assyrian cosmic influence. She had a colleague with her named Antak, but there was a freak surge in the Vortex and their TARDIS was damaged by a time spike. When they materialised they discovered they’d lost their time signature and with it their route map home. They tried to integrate themselves into the local populace, but their arrival had been observed and they found themselves being worshipped as gods. The people re-named Antak as Amun and Jane became Thoth. For a while everything was fine, but one year the crops failed and there was an uprising. Jane escaped into the Sudan, but Antak didn’t make it. The chameleon circuit disguised their TARDIS as a shabti figure, but it was stolen by Userhat and Jane has spent a dozen lifetimes since then searching for his tomb. When her TARDIS started to break down from decay and neglect, it began calling to her and she was able to follow its trail to the Valley of the Kings. Carter realises this is why Jane first approached him and suggested he dig at this site.

The Doctor tells Jane she has to kill her TARDIS by piloting it into the heart of a star. He offers to track her in his own TARDIS, materialise it inside hers and pull her to safety a split second before it’s destroyed. Jane isn’t keen to be taken back to Gallifrey to face the consequences, but he tells her she has no choice and he avoids her questions about what they‘ll do to her. By setting themselves up as gods, she and Antak committed a class 2 intervention and she knows the penalty is vaporisation.

Carter is still completely baffled as to what’s going on, but when Ace tells him he’s about to travel into space, he remembers Professor Petrie telling him to treat life as an adventure and grasp it with both hands. The Doctor takes Carter and his companions into his TARDIS and they make contact with Jane inside hers. The two Time Lords synchronise their ship’s co-ordinates and the Doctor begins a countdown. Then the scanner becomes affected by interference and the Doctor warns Jane that her temporal stabiliser is slipping. She tells the Doctor she’s sorry and he suddenly realises what she’s planning to do. He pleads with her to stop and tells the others she’s slipping back through time. The Doctor desperately tries to keep up with her, but she keeps slipping time tracks. He tells Jane he can speak on her behalf to the Time Lords and promises it’s not like it was in the old days, but it’s too late. Just before her image disappears from the scanner, she tells them to “remember Thoth”. The Doctor’s TARDIS is now too close to the sun, but even as explosions rip through the control room, the Doctor continues his attempt to save her.

On the island of Mendolovinia, the Doctor, Ace and Hex battle through the torrential rain and the mud and approach the front door of a large house. Their knocks are answered by an elderly lady, Mrs Crisp, but when the Doctor tries to introduce himself, she slams the door firmly in his face. Hex suggests they go back to the TARDIS, but the Doctor says he can’t. He calls through the letterbox and tells the woman he wants to talk to Dr Verryman as he has important information for him about “the code“. Eventually Mrs Crisp opens the door again and the Doctor explains that he picked the information up on his communication channel and he believes he can help.

Reluctantly, Mrs Crisp allows them to enter - much to Hex’s relief as they were all getting soaked. The Doctor sympathises as the island is a little off the beaten track, but Mrs Crisp frostily says Dr Verryman came here so he could work in peace. She takes them to a living room while she goes to consult with her master. The house has stone flooring and is lit with oil lamps, so Hex is surprised to learn that the year is 3380. Verryman is retired now, but he was once one of the foremost authorities on bio-engineering and although the Doctor’s never met him, he has read his books. This island is part of the Sphere of Influence, a planet almost completely devoted to the advancement of knowledge, and Verryman was one of its founders. Ace wonders why he’s sending out mysterious requests for help in triple-ciphered code on multiple frequencies. The Doctor regards himself as a genius twice over, possibly even three times, so he’s confident he’s can find the solution.

They decide to have a bit of a snoop around. The Doctor is sure he can feel a vibration, like the ghost of something mechanical, so they decide to try upstairs - which is a relief to Hex as he hates basements. Suddenly a door bursts open and an elderly man greets them in an exaggerated eccentric manner. The strange man introduces himself as Dr Verryman and asks the Doctor whether he’s solved the code, but before the Doctor can answer, Verryman bellows loudly for his housekeeper. Mrs Crisp arrives and he implores her to pop the kettle on. The Doctor asks Hex to go with her, and Hex is devastated when she tells him the kitchen is in the basement!

Wasting no more time, Verryman orders the Doctor and Ace to accompany him to his laboratory, which contains equipment that reminds Ace of a hospital scanner, but which the Doctor says is an Inductor. The patient is strapped inside and a series of probes identify the medical problem and begin treatment. The surgery is done with energy pulses and gravity manipulation, so there are no scalpels and no mess. But as the Doctor examines the equipment, he realises the settings make no sense. Verryman tells him the Inductor has been modified and it’s no longer intended merely to cure, but to restructure the human brain to suppress primitive desires and enhance the intellect. Ace asks why the machine is linked up to the antennas on the roof and Verryman admits that his plan is to broadcast improving pulses across the ether to benefit countless billions of people in an instant. By beaming out a unilateral brain operation across the Universe, he plans to augment and extend the mental capacities of the entire human race. Verryman proudly declares himself to be a genius, but Ace is determined to stop him. The Doctor isn’t sure they can as the process has already begun and they don’t know the code…

In the kitchen, Hex discovers there’s no sugar, no milk and no biscuits, but Mrs Crisp tells him she and Dr Verryman devote all their energies to his work and they don’t cater for visitors. She says she’s not a fool and she knows the Doctor didn’t send him here to help her make the tea. Hex has already realised she’s more than just a housekeeper. She tells him he has no need of answers if the Doctor’s solved the code, but if he hasn’t, then he might care to look at what’s in the third bedroom on the third floor. Then she leaves Hex and heads back to Dr Verryman with the tray of tea.

In the laboratory, Dr Verryman reveals that he was the guinea pig in his own first experiment. When he entered the Inductor it began to rearrange his neurons and re-order the structure of his brain and he could actually feel his own mind expanding. For a time, the doors of perception were flung wide open and he transcended genius, becoming the cleverest man who ever lived. But within hours he experienced a clouding of his consciousness and it became hard for him to reason or even to perform the most basic of autonomic functions. To counteract it, he entered the Inductor again, then again and again after that. Just 30 minutes ago he was nothing more than a simpleton, unable to tie his own shoelaces. Thanks to the intervention of Mrs Crisp, he was restored to the state he’s in now, but in another 22 minutes and 41 seconds the regression will begin again. The effect is accelerating and in a few short weeks it’ll become permanent. Ace isn’t sympathetic and says he brought it upon himself, but the Doctor isn’t sure the equipment is to blame.

Ace wonders what all this has to do with the code and Verryman points out that she seems to have all the answers, while the Doctor seems to be finding it harder and harder to think. Verryman suggests the Inductor might have activated something dormant in his mind, a malign presence which feeds off the intellect, like a pernicious virus. Unchecked it could result in the regression of any infected human brain down to the level of homo erectus, a base savage with an average IQ of just 45. Even the greatest genius that ever lived couldn’t hope to cure such a virus between interludes of idiocy. The Doctor starts to stumble over his words and he appears increasingly confused. Verryman says he translated the virus into a code, a series of data statements that give a mathematical description of its structure, then he used the Inductor to broadcast the code in the form of a puzzle. Ace realises he set a trap for the Doctor, who was compelled to come here. The truth suddenly dawns on him - everyone who reads the code becomes infected, which means he too now has the virus.

Hex slowly makes his way to the third bedroom on the third floor. He finds the door is bolted, which isn’t a very encouraging sign. He opens the door and peers inside, but it’s completely dark. He calls out and hears a low inhuman voice. Suddenly the door slams shut behind him and he hears the bolts being slid back into place. He bangs on the door and demands to be released, but Mrs Crisp calls back to him and says she trust he’ll find the answers he was looking for. Hex hears a second inhuman voice and the clanking of chains. As he becomes accustomed to the darkness, he discovers he’s sharing the cell with two ape-creatures like hominid cavemen…

Ace asks how a code could rot someone’s brain and Verryman explains that it’s a sequence of instructions designed to set up a chain reaction in the victim’s neural pathways. The Doctor is now mumbling incoherently and struggling to make any kind of sense. Ace slaps him to snap him out of it, and for a moment it seems to work. He accuses Verryman of being completely irresponsible and endangering all intelligent life in the Universe. Verryman says he didn’t create the virus and he’s as much a victim as the Doctor and now he needs the Doctor’s help to save them both and preserve his genius. The Doctor admits that he doesn’t have the answer, but Ace reminds him he’s supposed to be a genius three times over. The Doctor says they’re running out of time and the only way he can solve the code is to enter the Inductor himself and enhance his own intelligence.

Mrs Crisp arrives with the tea and casually asks how the work is going. Ace asks her where Hex is and she tells her he’s dying. Ace is furious and races out of the laboratory, but when the Doctor goes to follow her, Mrs Crisp holds him back. When she locks the door and orders him to climb inside the Inductor, the Doctor realises she’s more than just a housekeeper. Dr Verryman assures the Doctor there’ll be no pain involved in the enhancement procedure, but the Doctor is now so confused he can only respond with gratitude. Mrs Crisp tells him he’s the progenitor they’ve been looking for and reveals that Verryman failed in his task, just as the others did. She explains that a Professor Caldeer and his student previously answered their call for help, but the process was too much for them. Verryman asked what happened to them and she tells him they’re being kept in the third bedroom on the third floor.

Ace runs through the house, calling for Hex. Eventually she arrives outside the bedroom and hears Hex on the other side of the door. She opens the door and peers inside, and she too is horrified to see the two chained cavemen. Hex assures her they won’t attack so long as she remains calm. From what she’s already learned, she tells Hex the two ape-creatures are homo erectus who have an IQ of just 45. Just then the door slams shut behind them and with no door handle on this side, they’re now both trapped inside. Ace tells Hex that the code is a virus that infects anyone who reads it and causes them to regress into cavemen. One of the creatures reacts to her words and starts repeating Dr Verryman’s name. Ace realises they still have a remnant of their original memories left, which just makes her even angrier. The two cavemen begin to get aggressive and struggle against their chains and with the help of Ace and Hex, they pull the chains away from the wall…

In the laboratory, the Inductor programme starts to respond to the Doctor’s brain patterns and Verryman is confident it won’t take much longer. He tells the Doctor he intends to isolate his neural network within a telepathic projection field, and although any enhancement will only be temporary, the Doctor hopes it’ll be long enough to enable him to find a solution. Verryman begins downloading the programme and sparks of energy pour through the connections leading into the Doctor’s brain. Suddenly his eyes snap open and he tells Verryman they’ve both been tricked. He now knows that the solution to the code isn’t a cure after all, it’s a conversion programme that changes energy into projected matter. The virus uses technology as a carrier to help spread itself, so solving the code will only release the virus and make it airborne.

The Doctor demands to know what Mrs Crisp’s part in all this is and she reveals that she’s a member of the Order of Simplicity, who exist to destroy the corruption of technology. They feel life should be simple and pure, as nature intended, and they believe technology smothers natural impulses. She accuses the Doctor and people like him of denying reality, but he argues that progress and intelligence are all part of that natural order. Verryman points out that for a group that rejects all technology, his Inductor seems to play a large part in whatever they’re planning. The Doctor agrees and says hypocritical maniacs are always the worst.

Mrs Crisp says the Order of Simplicity heard about Verryman’s machine and they feared it would push mankind too far towards enlightenment, so she came here under the guise of a simple housekeeper. All this time they’ve been waiting for Verryman to succeed, then she programmed the virus into the Inductor to deliberate infect him. The alien virus has been in their possession for many years, and although its origins are unknown to them, they don’t mind as they believe ignorance is bliss. When Verryman broadcast the code, he unwittingly showed them its true potential and they now plan to regress all intelligent life in one go forever. The Doctor points out that if he refuses to find the solution, the virus can never be released, and he says he’d rather regress to an IQ of 45 than infect everyone with the plague. Mrs Crisp is convinced that once he becomes fully enhanced, he won’t be able to resist the temptation of solving the code, which proves her point that intelligence itself is the real virus.

Suddenly the door bursts open and the two cavemen charge into the laboratory, followed by Ace and Hex. Verryman is horrified to see the scientists have become mindless animals, but Mrs Crisp admires them as pure and uncomplicated. She orders Verryman to increase the power to the Inductor so that the Doctor’s hungry mind will be unable to resist releasing the virus. The Doctor agrees and urges Verryman to do it quickly. Mrs Crisp is delighted and believes the Doctor’s intelligence is already feeding his own destruction, but then her attention is taken by the advancing cavemen. Even as the ape-creatures pummel her to death, she gives praise to the age of purity that she believes is coming. Ace and Hex watch in horror, but Verryman is satisfied she got what she deserved. Hex thought the creatures were after the machine, but in fact they’re now just standing there, as if waiting.

The Doctor warns everyone to stay back as it could be dangerous, but they notice he’s speaking to them without moving his lips. Verryman explains that they’re hearing his thoughts through the telepathic amplification field. The Doctor tells them he’s going to think himself down to an IQ level of 45, then he blacks out as the ape-creatures howl in agony. As the laboratory equipment starts exploding, Hex rushes to release the Doctor from the Inductor. With Ace’s help they free him just as the room begins to collapse around them. The two cavemen attack the now empty Inductor and although the Doctor weakly mumbles that they must save them, the others realise they need to get away before it’s too late. The entire house erupts in flames and they hear the screams of the creatures as the ceiling finally caves in.

In a back-street London pub, two of the patrons approach their friend Joey Carlisle and try to persuade him to buy them a drink. They’ve seen him flashing his cash around, but then they tease him because now the war has ended, there’ll be no more need for a black market and he’ll have to get himself a proper job. Joey laughs and says he’s sure the rationing will be around for a long while yet. He’s approached by the local constable PC Ernie Miller, who grabs him and throws him through the door and into the gutter. The officer asks him where he was on Tuesday night when a van overturned just off Clapham Common and the driver was left for dead while someone made off with the cash. Joey denies all knowledge, but PC Miller says they have a witness who’s down the station right now giving them a statement. He goes to handcuff Joey, but notices an expensive looking bracelet on his wrist. Joey laughs and says it’s no ordinary bracelet. He presses a button and PC Miller immediately staggers from a headache. Then, oddly, the officer starts to reveal incriminating facts about his gambling habit. Joey threatens to reveal Miller’s secret, but they both come to an agreement to keep quiet. Joey switches off the bracelet and sends the policeman on his way, warning him not to try bothering him again. He’s delighted with his new-found power. Everyone has secrets, but they can’t keep them from Joey Carlisle any more…

The TARDIS materialises and the Doctor, Ace and Hex emerge to find themselves outside the London pub. Ace is far from pleased as she recognises ‘The Four Barrels’ and knows exactly where they are. This is Streatham and her mum grew up not far from here. The pub used to be her local and she remembers the place being very quiet, yet tonight it’s obviously doing a roaring trade. The Doctor reveals that it’s 9 May 1945 - otherwise known as VE Day, which signifies the end of the Second World War. The Doctor uses a detector to search for psionic energy and picks up a powerful but erratic signal. They head off in the direction it’s coming from…

In one of the nearby houses, May Carlisle prepares a drink from powdered milk for the young girl in her care. She hopes her son Joey will be back soon with some condensed milk, after which they can get Audrey back to her mother. To her horror, she finds the three-year old girl hiding in the sideboard, so she quickly pulls her out and warns her not to go in there again. Audrey starts to cry, so May explains that Joey keeps all sorts of stuff in there and he doesn’t like anyone messing with it. Before she has a chance to tidy up, Joey returns home and discovers what’s happened. He becomes angry and threatens to punish Audrey, but May demands to know why he’s been keeping electrical goods hidden away in her house. He tells her it’s none of her business and denies that the goods are stolen, claiming he bought them off some sailors down by the dock. He keeps looking out the window and May wonders if someone’s after him.

The Doctor’s detector leads them to Old Terrace. He deduces that the origin of the trace has been in motion recently, but it’s stopped now, right by one particular house. Ace assumes this must be some sort of joke on the Doctor’s part as the house is next door to the one where her own mother lived as a young child towards the end of the war. If this really is 1945, Kathleen and Audrey are probably in there right now. The Doctor assures her it’s nothing more than an unforeseen complication and suggests they quickly investigate the matter and be on their way. He knocks on the door.

May peers through the curtains, but Joey tell her not to let the visitors in. When she realises he thinks they might be the police - or worse - she realises she was right all the time about her son being a thief. He tells her to stay away from the window, but it’s too late as Hex saw the curtains twitch. The Doctor calls through the letterbox and says he needs to speak to them on a very important matter. The door opens and May asks them what they want. The Doctor introduces himself and his friends, but May tells them her son Joey isn’t at home so they’ll have to come back later. The Doctor’s detector starts activating again, so they push past the old lady and enter the house, warning her she could be in great danger. Hex quickly searches the house and discovers their prey has escaped via the back door. The Doctor and Hex chase after him and ask Ace to stay behind to see what she can find out about Joey. Once they’re alone, May tells Ace she has no right to barge in. Then she looks at Ace more closely and wonders where she knows her from. Just then, Audrey enters the room and when Ace sees her, she becomes worried about the girl’s health. When she realises how hot the girl is, she says she wants the Doctor to take a look at her.

The Doctor and Hex arrive at a nearby café and order tea for themselves and offer an open invitation for Joey, who’s hiding in the corner behind a newspaper, to order whatever he wants. As they sit at his table, Hex rebukes Joey for smoking and tells him he probably could have outrun them if it wasn‘t for his habit. The Doctor produces a flashing low-band psionic detector and tells Joey it reveals that he‘s in a lot of danger. Joey thinks he knows who the Doctor and Hex are working for and asks them to pass on the message that “she’s” wasting her time and that he doesn‘t know anything.

May sends Audrey to bed and tells Ace she’s had six children and knows what’s best for them. They both agree that Audrey and her mother Kathleen are lovely, but May is curious about how Ace knows so much about them. Ace claims they met at the War Office, and this seems to satisfy May as she knows Kathleen doesn’t talk about her work. While May goes to make a cup of tea, Ace decides to snoop around the living room, and when May returns she finds Ace has discovered Joey’s secret stash of electrical goods. The old woman insists her son isn’t involved in anything illegal, but Ace reveals that the goods are actually alien in origin. May assumes she means they’re foreign and says that’s OK as it means they haven’t been robbed from anyone local. Ace promises she’s not here to hand Joey over to the police, but warns that the electrical goods have travelled a lot further than just across the Channel.

In the café, the Doctor and Hex are celebrating VE Day with cakes. Joey asks them what Miss Merchant has been saying about him and adds that she’s been telling people he was seen near a van that crashed. The Doctor is intrigued and asks more about the van and Joey reveals that the goods inside were the property of the Forge. The Doctor is horrified and warns Joey not to get mixed up with them. Hex remembers the Doctor mentioning the Forge once before, but the Doctor obviously doesn’t want to go into more detail. Joey denies any involvement in the robbery, but the noise from the psionic detector suggests otherwise. It points towards Joey’s bracelet, and when the Doctor and Hex ask him to hand it over, Joey reacts instantly by hurling the table into the air, knocking them off their chairs and sending plates and cups flying. Joey flees into the night and the Doctor tells Hex that the bracelet must be damaged as the psionic reading is increasing. They need to retrieve it before it does any real harm…

May is worried that her son is in trouble, but Ace assures her that’s not why she’s here. Nevertheless, the old woman tries to bribe her with some of Joey’s stolen petrol coupons. Just then a van pulls up in the street outside and a mysterious woman, accompanied by three security guards, heads straight for the Carlisle house. Ace whispers to May to go upstairs and barricade herself and Audrey in, then she answers the front door. The woman says her informant has directed her to this address and if she’s allowed to collect the item she wants, it’ll spare them all a lot of trouble. Ace says she doesn’t know what she’s talking about, but the woman has her own flashing psionic energy detector. She orders her guards to ransack the house and when Ace tries to stop them, a fight breaks out…

Joey hurries down the back streets, not looking where he’s going, and bumps straight into the two friends he met earlier in the pub. They tell him they’re heading up to Trafalgar Square to see the fireworks and invite him to join them, but Joey angrily tries to push past them. They see the expensive looking bracelet on his wrist, so Joey decides to demonstrate its powers. He switches it on to full blast and the two friends cry out in pain…

May slowly moves downstairs to find out what’s going on and finds Ace unconscious in the hallway. As she recovers, Ace discovers she’s got a bloody nose and tells May the mysterious woman had a mean right hook. The woman and her men drove off a few minutes ago and it looks like they’ve taken all of Joey’s stolen goods with them. May is mortified, but Ace tells her it’s probably for the best. She just hopes the Doctor and Hex catch up with Joey before the woman does, because it’ll take more than TCP to fix what she has planned for him…

The Doctor and Hex have lost Joey in the back streets and they’re unable to trace him using the psionic energy detector because there’s been a large outpouring of energy in the vicinity recently. They encounter Joey’s friends who are both sitting in the gutter, looking vacant and considering the hopelessness of their existence. Hex tells them they’re after a man who came this way recently and the friends immediately identify the man as Joey Carlisle. The Doctor realises the bracelet must be a Truthsayer, devices that belong to the Deons, law keepers from the Anurine Protectorate. They’re space police and the Truthsayer bracelets force their captives to reveal the truth. Hex tests the theory by asking the friends which way Joey went and they point them in the direction of a warehouse next to a nearby railway. The Doctor and Hex race off…

When they arrive at the warehouse, Hex says it looks like a bomb hit the building…then he remembers where and when they are and realises that’s exactly what happened. They shout out Joey‘s name and he immediately calls back from the shadows and tells them to leave him alone. The Doctor says they need to deactivate his bracelet as it’s damaged and is hurting people. Joey refuses to hand it over, then he switches on the device and starts asking his pursuers questions. Unable to resist its power, the Doctor reveals that the Forge is a secret organisation that collects alien technology that they plan to use to take control. Joey starts to get suspicious when Hex reveals that the three-year old girl from next door is Ace’s mother. He asks Hex what his relationship is to Ace, but he gets his answer straight away just by looking at Hex’s eyes - he’s not her boyfriend, but he wants to be. Given that Ace’s parentage is so convoluted, Joey casually asks about Hex’s background…and the Doctor is forced to reveal that Hex’s mother is -

Before he can continue, they’re interrupted by the arrival of the mysterious woman from the Forge, together with her security guards. The woman fires at Joey with a laser pistol and he screams in agony. Released from the power of the bracelet, Hex rushes over to administer first aid, but he’s horrified by the sight that greets him. The Doctor rebukes the woman and tells him there was no need for that, but she tells him Joey stole from them and lied to her. She believes losing a hand is a fitting punishment for his crimes. The Doctor reveals that he knows Miss Merchant’s identity and that she owns a psionic detector. She finds him curious and says it’s a shame the bracelet is now too damaged to use on him. Hex says Joey has gone into shock and the Doctor asks him if he remembers the van and the bracelet. Joey admits stealing it and also reveals a string of previous crimes and robberies that he and his friend committed in the past and plan to commit in the future. Miss Merchant explains that the psionic leakage has permanently damaged him and turned him into a thief who’s unable to lie. The Doctor tries to stop her leaving, but Hex says their priority is getting Joey to a hospital. Miss Merchant turns to them with one final word of advice - not to bother trying to tell the truth about what happened here as no one will believe them.

In the house on Old Terrace, Joey’s mother screams uncontrollably when the Doctor breaks the bad news about what’s happened to her son. Ace asks if Joey’s going to be alright, but Hex says that although he’ll live, he’ll never be the same again. Ace isn’t sure that’s a bad thing and Hex adds that at least he’ll have his mum to look after him. Audrey is asleep, but Kathleen is due back any time now, so Ace wants to leave immediately. Hex suggests she say goodbye to Audrey before they go and reluctantly she goes upstairs. Once they’re alone, Hex asks the Doctor what he was going to say about his mother back at the warehouse. The Doctor is about to reveal everything when Hex interrupts and says he realises the Doctor was lying all along, but he‘s curious to know how he was able to do it while under the influence of the Truthsayer. The Doctor simply explains that they all have their secrets.

The Doctor, Ace and Hex are being interrogated by a hostile officer, Captain James Hurst, inside a maximum security military bunker. No one could have got in without clearance, so he demands to know how they did it and who they’re working for. Not for the first time, Ace explains who they are, and Hex insists they’re good guys, but the Captain doesn’t appreciate being taken for an idiot. The three of them arrived ten minutes after a delegate was murdered here and he doesn’t believe in coincidences. Hex wonders why they always blunder into a murder investigation rather than a party and Ace suspects the TARDIS is programmed to hone in on trouble. Captain Hurst repeats his questions again and reminds them they’re in an extremely precarious position.

The Doctor is surprised to discover they’re in the Ranulph Fiennes Bunker in Antarctica. Captain Hurst explains that the year is 2045 and the Doctor realises they’re in the middle of some top secret peace talks at the height of the second Cold War. He tells the Captain to stop wasting time questioning them and find out who really committed the murder before the whole planet goes into nuclear meltdown. Before Hurst can react, the door opens and Commander Claire Spencer enters and tells him to wait outside. As soon as she’s alone with the travellers, she welcomes the Doctor wholeheartedly and explains that although he doesn’t know her, she knows him very well by reputation. She’s in charge of this facility and is one of just 34 people on the planet with access to the UN files about him. She tells him time is of the essence and then she pulls rank to re-draft him back into his former position of chief scientific advisor.

She explains that the murder victim was Alexander von Gratton, the American consul to the Far East. He was found shot dead in his room about half an hour ago and as the world is politically volatile at the moment, the accusations are already flying. She needs to find out who killed him fast, but there are no suspects and the whole situation appears to be impossible. As this is one of the most secure facilities on Earth, everything is monitored by state-of-the-art systems and the only thing that could get away with murder here is a ghost. The Doctor refuses to rule anything out (even a ghost with a gun) but first he needs Claire to tell him everything there is to know about this bunker.

They head for the control centre and Hex describes the place as a cross between Buckingham Palace and the Death Star. Security is paramount here and the monitoring arrays can tell where everyone is at any time of the day or night. Claire takes them into a lift which starts to descend and Hex is relieved to discover they’re not going to the basement. The bunker is 450 miles from civilisation and any movement in a 200 mile radius is investigated via satellite. The Doctor is impressed and asks whether one of the delegates themselves could have brought something unpleasant into the bunker. Claire says that with all the scans, checks and fail-safes here, they‘d have spotted anything unusual. In fact, the delegates don’t even wear their own clothes while on site and things like phones, computers and even writing materials are all banned. There’s only one book in the entire facility - the Bunker Protocol Guide. Ace wonders how the base can remain top secret and private if they do all this recording and monitoring and Claire explains that they wipe and re-boot the entire system every 45 hours. No data is ever stored here and apart from the distress signal (which can alert all the military forces off the coast of Antarctica) there are no transmitters. It’s a complete information dead zone. Unfortunately the distress signal has already been activated because of the incident, which means every nation is scrambling to collect their delegates right now. They have three quarters of an hour before they arrive and then they’ll have whole armies accusing each other of murder.

It doesn’t take the Doctor long to get to grips with the bunker’s comprehensive systems. Hex flicks through the Bunker Protocol Guide and finds Section 4.5 which refers to ’Managing Security in the Laundry Department’. Ace contacts them via walkie-talkie and says that with a bit of arm twisting, she and Captain Hurst have convinced the delegates to go over to the TARDIS. Hurst has told the delegates the ship is a highly sophisticated panic room, but now that they’re approaching it, it looks more like a wooden box to him. He also mentions that the delegates are starting to wonder why they don’t need their translators any more. Commander Spencer promises to get back to him with some answers soon, but tells him to hurry up and get the people inside so they’ll be free to solve the mystery.

The Doctor asks the computer to show him the last recorded movements of Alexander von Gratton. They watch the CCTV footage as von Gratton left the bar, walked down corridor 4 towards room 5, which was guarded by two soldiers. Claire is unhappy when she sees that one of the soldiers, Private Fenton, was preoccupied telling jokes to his colleague and didn’t see von Gratton until he was right next to him. The delegate then went inside his private room and they lose the CCTV footage of him exactly 4.5 seconds later. Then they hear a noise from inside the room and watch as the two guards rushed inside to investigate, but found the room was empty apart from von Gratton, who was already dead, having been shot in the forehead and the heart. Apart from von Gratton himself, no one entered or left the room that day prior to his death. The Doctor has a strange idea that something important is happening, but he can’t quite grasp it. He asks the computer to play back random short dialogue recordings from the last 24 hours and they listen to a series of short clips taken from all over the base. Claire wonders if the Doctor is just hoping to get lucky, but he reminds her not to confuse complexity with chaos. He’s got the strangest feeling the answer has been under their noses the whole time.

The Doctor suddenly leaps at one particular extract which mentions the number 45. He realises this is what’s been eluding him. He asks the computer to play back every extract in which that number, or any of its numerical of linguistic composites, appears. They sit back and listen as the computer bombards them with clip after clip containing the number 45. Hex thinks it must be a coincidence, but the Doctor learns there’s been one recorded use of those words every four minutes and fifty seconds and the total number of instances is 4,545. Suddenly the Doctor realises it’s an energy signature. He explains that there are countless billions of dimensions and some of them are incomprehensibly different to our own. Beings from these distant dimensions obey very different laws of physics and they’re never meant to come here. He asks the computer to search for any phrase or short linguistic structure that’s been repeated 4.5 times in the last 45 minutes and it finds just one example - Private Fenton’s joke from the CCTV recording. The Doctor says it‘s actually a complex linguistic structure using a chameleon meme to disguise itself as a joke. In this case, the joke is a spaceship, like a non-physical TARDIS (he calls it a CORDIS - a Conveyance of Repeating Dialogue in Space-Time) and the 45s they’ve been hearing are the pulses of its engines.

Ace contacts them again on the walkie-talkie once the delegates are all safely inside the TARDIS. The Doctor tells her to look underneath the console for a small red switch near the central column. She finds it, but is unable to press it because it’s protected by a welded panel. The Doctor is angry with himself when he remembers he sealed it up himself. He tells her she’ll have to find a way to get the panel off - but before she can respond there’s an enormous explosion of light inside the TARDIS and a man suddenly appears from nowhere. Captain Hurst challenges the man as the delegates back away in fear, but the new arrival has a gun too and the control room is filled with the sound of laser fire. Ace is horrified to discover the man has shot dead six people!

She demands to know who he is and he nonchalantly tells her he‘s Nobody. She repeats her question and he tells her again that his name is Nobody No-One, otherwise known as the Word Lord. He says he’s a renegade from a reality 45 billion dimensions away. He assures her he’s not insane, but she’s not the first person to think he is. He wonders if he’d get a better reaction if he changed his hair style. Ace tells him these people are under her protection and she orders him to leave, and he‘s greatly impressed by her pluckiness. It’s been so long since anyone‘s told him what to do, he’s actually missed it. He invites her to tell him not to shoot anyone. Captain Hurst has heard enough and he opens fire on the strange man, but his gun fails to work. Nobody points out that while they‘re inside the TARDIS the soldiers are subject to the law of temporal grace, but those laws don’t apply to him. He demonstrates by murdering Captain Hurst in front of the delegates. Then he invites Ace to tell him not to shoot anyone else. Furiously she charges towards him, but be knocks her to the ground without any effort.

The Doctor‘s voice calls out to Ace over the walkie-talkie and Nobody No-One decides it’s time for a proper visit. In the bunker, the Doctor realises Ace needs help, so he sends Hex and gives him a thermo-spanner to use on the panel under the TARDIS console. The Doctor tells Claire they’re up against a Word Lord, a being from a dimension made of language and communication, not matter and energy like ours. He asks the computer to play back any recordings made recently containing the words ‘nobody’ or ’no-one’. They listen to several of the examples (which includes Captain Hurst saying nobody could get into the bunker without clearance, and the Doctor saying nobody can get inside the TARDIS) and they realise that just saying those words is enough to make them reality for a Word Lord. As soon as somebody says nobody or no one could do something, then that’s exactly what the alien is able to do. Suddenly there’s a flash of light and Nobody No-One appears in the room with them. He explains that he’s a linguistic entity and says his CORDIS can project to him any tools or weapons he happens to need. It also makes him indestructible, like an alternative version of the Doctor but one who’s a bit more ‘God’ and a bit less ‘gnome‘.

Hex arrives at the TARDIS and rushes in to check on Ace. He finds her recovering on the floor and tells her the survivors from the bunker are in the corridor outside the control room. She assures him she’s fine and refuses to let him check her for damage. He shows her the thermo-spanner and tells her it should release the panel under the control console - but then he realises he doesn’t know how to operate it!

Commander Spencer holds Nobody No-One at gunpoint and tells him to stay where he is. The Doctor warns her that it won’t do any good and even Nobody is getting tired of reminding people that he’s immune to their weapons. Claire reveals to the Doctor that she lied when she told him she didn’t know him. She met him once, years ago when she was in Special Forces, but she doubts he’ll remember it as he was older then. It was a really rough situation and she was scared out of her wits, but he told her it was good to be scared and not being scared was something to be scared of. The Doctor appreciates what she‘s told him and he gently persuades her to lower the gun. He turns to Nobody No-One and asks why he‘s been following him. He now realises he’s been encountering references to 45 for several weeks now, long before they arrived here. Nobody admits that his CORDIS is old and he kept missing the Doctor, but it was worth the wait. He reveals that he‘s a bounty hunter and he has a list of the most powerful, resourceful and dangerous beings in the entire multiverse. He’s happy to track them down and sell them on, but although there’s a fantastic reward on the Doctor‘s head, it’s not the money that matters to him. His reward will be the satisfaction of seeing the Dalek Supreme’s eye-stalk light up when he hands the Doctor over…dead. The Cybermen have also put up a reward for the Doctor, but they only want his brain, so Nobody is planning to take his brain out and meld the head back together so everyone gets what they want. He’s even had a couple of offers for Ace and Hex, although disappointingly the reward for Hex was very small.

The Doctor stands firm and announces that he’s not going to let Nobody harm anyone else. Nobody points out that the Doctor is used to shouting at people with guns and never getting shot, which has made him over-confident. The Doctor laughs and reveals that all he’s been doing is keeping Nobody talking while his friends get ready to act. He whips out the walkie-talkie and orders Hex to flick the switch under the console now! Unfortunately he gets no reply and Nobody says this confirms what he was saying about the Doctor being over-confident. He raises his weapon and opens fire…

In the TARDIS, Hex is struggling to get the thermo-spanner to work and Ace is no help. Eventually it occurs to him that the device needs to be changed to setting 45. It works and they start to remove the panel covering the switch.

As the Doctor comforts the dying Commander, Nobody No-One says he can’t understand why she stepped in the way of his laser. With her last breath, Claire tells the Doctor she did it to buy him the time he needed. Nobody shrugs indifferently and raises his weapon again to shoot the Doctor. Suddenly Hex’s voice comes over the walkie-talkie and tells the Doctor they’ve managed to get to the switch. The Doctor reveals that the switch controls the TARDIS’s translation unit and he shouts to Hex to press the button immediately. Nobody realises he’s been beaten, but as he tries to taunt his nemesis, his words become completely incomprehensible.

Later, the Doctor, Hex and Ace watch in amusement as the international delegates celebrate their release back at the bunker. Thanks to their recent brush with death and a few bottles of brandy, they’re acting as though they’ve always been the best of friends. Hex admits that he’s still confused about what happened, and the Doctor explains that once the TARDIS’s translation unit was set to reverse, it began translating the words and thoughts of everyone into languages they couldn’t understand. It was as though everyone had started speaking in tongues. Then the Doctor reset the bunker’s computer system to delete every recorded word. With no spoken language to support them, their enemy (who cannot be named for fear of bringing him back) and his CORDIS were forced to take refuge inside the only printed text within hundreds of miles - the Bunker Protocol Guide. Hex flicks open the book and reads the story of a man who is frozen within the pages themselves. The Doctor slams the book shut quickly and warns that one wrong word could let their enemy out again.