The Doctor proudly tells Lucie that they’re currently travelling at 67 kilometres an hour, which is two above what the train’s top speed is supposed to be. He thinks it’s a lovely piece of engineering, but Lucie is far from impressed and laughs at the thought that he’s just a train-spotter at heart. He probably even has a notebook and licks the pencil before he writes in it. Although she admits it’s been a good trip, she really wishes she could listen to her MP3 player. Unfortunately it’s 1898 and she knows the consequences for the timeline could be disastrous. The Doctor suggests they go for something to eat, but she’s not hungry and decides to go up to the observation car instead.

Elsewhere on the train, Karen - Lucie’s former colleague from Hulbert Logistics - surprises security officer Henrik by knocking out the guard on the door, picking the lock and entering his compartment. He asks her what she wants, but she knows he’s playing dumb because there’s only one thing on the train she could want. She promises not to shoot him in the foot if he tells her where it is…

In the dining car, the man on the table next to the Doctor introduces himself as Frederick Simonsson and asks if it’s his first journey on the electric railway. The Doctor admits that he came here especially to ride it and Simonsson is delighted, but says he hopes he’ll also take advantage of the other attractions Stockholm has to offer. The Doctor is quite interested in the new play by Strindberg and Simonsson tells him the King is also an admirer and he once invited the author to his court to discuss his work. Simonsson explains that his job is to acquire art on His Majesty’s behalf, some of which are donated to museums and others are displayed in his own residencies. He considers himself doubly lucky because the King’s tastes are similar to his own, so he’s never required to purchase anything gauche.

As Lucie nudges her way through the crowded carriages, she’s surprised to bump into Karen coming the other way. She’s particularly surprised as she thought her old colleague was dead. Karen laughs at the suggestion and says she’s never been better. Lucie wonders what she’s doing in Sweden in the late 1890s, but her friend causes a distraction and runs away before she can ask her any more awkward questions. Lucie shouts out to the other passengers to stop Karen, but it’s too late.

The Doctor and Simonsson are engaged in a very informed conversation about art, and when they start discussing one particularly energetic artist, the Doctor describes his work as streets ahead of any of his contemporaries. Simonsson is forced to disagree and says his own personal quest is to elevate recognition of a man who he feels is perhaps Italy’s greatest artist. He doesn’t expect the Doctor to have heard of him as very few people have, but when he reveals the artist’s name is Claudio Tardelli, the Doctor is visibly shocked. The Doctor thought very few examples of his work still survived and Simonsson agrees but says he’s determined to locate any remaining pieces and bring them all together. He says he already has two paintings and a statue, but by chance he happens to be on his way back from acquiring another of Tardelli’s works of art. Before he can explain further, they’re interrupted by the arrival of Henrik who announces with alarm that they have a thief aboard the train!

With Lucie chasing not far behind her, Karen knocks aside anyone who gets in her way and eventually comes to the end of the train. She opens the carriage door, expecting to see her partner in crime waiting on a hover-platform, but in fact the Headhunter has decided to get into the spirit of the times and is instead charging alongside the train on horseback. It may be less conspicuous, but as Karen points out, it’s not so easy to jump onto from a moving train. Karen successfully leaps across just as Lucie arrives. She’s surprised to see the Headhunter there too, but there’s no time for a reunion as her former enemy has places to go and priceless artefacts to sell. Karen confirms that she has what they came for, so they both ride off into the distance, leaving Lucie behind in frustration.

The Doctor tells Simonsson he has some experience in this sort of thing and offers to help him retrieve Tardelli’s stolen work. Simonsson assures him that won’t be necessary as in fact the piece was never on the train in the first place - the thieves have stolen a decoy! The Doctor asks where the genuine article is, but Simonsson says he‘d prefer not to reveal that. Instead, he has something else the Doctor might find interesting. He produces photographs of Tardelli’s other works of art, which he’d brought along to convince the owner of the latest piece that he was sincere in his intention to purchase it as part of a collection. The King intends to display them all at the Drottningholm Palace after the renovations, but that might take years and Simonsson is trying to persuade him to put them in the Nationalmuseum instead. He shows the Doctor a photograph of a portrait that wasn’t known to exist until he purchased it four years ago, then he pulls out another picture which is particularly rare as the artist rarely painted classical scenes. The Doctor confirms that Tardelli had no interest in the past and would never have chosen to paint such a picture unless he was commissioned to do so. The next image shows Tardelli’s homage to Botticelli’s Mars and Venus. Simonsson then produces his favourite item - a photo of Tardelli’s only known figurative sculpture. The Doctor is amazed and Simonsson says he’s very keen to put this one on display as he thinks it could revolutionise their entire view of art history. The Doctor describes the sculpture as abstract and Simonsson agrees that’s the very word he’s been searching for.

The Headhunter and Karen bring the horse to a halt as soon as they’ve reached a safe distance. Karen says she isn’t cut out for all this ‘Butch Cassidy’ stuff and insists that the next time they plan to rob a train, they do it some time after the invention of the motorbike. The Headhunter asks to see the diamond and as Karen reaches for it, she comments on how it’s different from any other diamond she’s ever seen. The Headhunter reveals that it’s only called that by people too primitive to understand what it really is. Unfortunately she soon discovers that the object stolen by Karen is a fake! The Headhunter admits that she thought this might happen as a decoy is a pretty obvious ploy. She tells Karen that compared to what they have to do next, the robbery on the train was a doddle.

Lucie joins the Doctor in the dining carriage and delights in surprising him with the news that the theft everyone’s talking about was committed by none other than her former work colleague Karen. He only vaguely remembers her and seems to recall that she was supposed to be dead, but when Lucie adds that she escaped with the Headhunter, it all becomes clearer. She asks the Doctor what was stolen and he reveals that it was a work by an obscure 17th century artist called Claudio Tardelli. He also explains that the reason Tardelli is obscure is because the Doctor has done his level best to keep him that way. He says he first encountered Tardelli on a visit to Rome and discovered that wherever his works were displayed, they warped the fabric of reality, even to the extent of changing the people that looked at them. Despite appearances, Tardelli wasn’t human, and he was trying to gain influence over the Pope. The Doctor had him discredited, but he got away and ended up in Florence, and ever since then the Doctor has destroyed any samples of his work he could find - and he’s very disturbed to learn that King Oscar has some examples in his home! The King is highly respected on the international scene as a fair and unbiased arbitrator, so if he ends up being influenced by Tardelli’s paintings, who knows what will happen. Now that the Headhunter is involved, the Doctor is even more concerned. Lucie says the object stolen by Karen was too small to be a painting, but whatever it is the Doctor can’t let it fall into the wrong hands. It means they’re going to have to steal it first!

The Doctor checks the time with Lucie, then they go for a stroll around the Drottningholm Palace, which was built on an island. He says he can’t relax knowing those paintings are inside, but they can’t just land the TARDIS inside without knowing exactly where the art is kept as the noise will just attract attention. He’s confident that if the pieces are all kept in the same place, they can get them in one manoeuvre, but he needs Lucie to get them some information first.

Not far away, the Headhunter and Karen are hiding outside the Palace when they see the Doctor and Lucie approaching. Acting casually, they start to put their plan into action. The Headhunter directs Karen’s attention to the guard standing on the east wall, but Karen realises he’s the man she knocked out on the train so he‘ll recognise her. Another man is going up the steps and Karen thinks he’ll be a much better candidate…

Henrik goes up the steps and checks in with the guard. There’s been no news yet and Henrik is far from happy. He remembers a time when nobody would dare steal from His Majesty as it’s unpatriotic, but times are obviously changing. Muttering to himself, Henrik leaves the guard standing on duty…

Not far away, Lucie is watching the guard from her hiding place, willing him to turn around. Acting casually, she starts to put the Doctor’s plan into action. She approaches the man and deliberately faints at his feet. The guard rush over to see if she’s alright and she puts on a very fake ’posh’ accent and accuses him of being a petty crook, trying to rob her. The guard assures her she’s safe with him as he’s a member of the Royal Guard. He offers to get a doctor but she asks him to stay with her. She compliments him on being a very ’pleasant gentleman’ and says she’d feel a lot better if he could help her to a restaurant where she could get something to eat. The guard says he can’t do that, but when she says she fears she might faint again without his assistance, he reluctantly agrees to accompany her.

The Headhunter and Karen have witnessed everything and wonder what they should do now that Lucie has beaten them to the guard. Karen is sure the Doctor and Lucie will mess things up for them, but the Headhunter thinks it might actually work to their advantage.

In the restaurant, Lucie is doing her best to keep the guard Anders distracted. She introduces herself as Ms Palmer-Tomkinson and offers him more wine, then urges him to tell her more about his work as she finds it fascinating. Anders boasts that he has a very responsible job but it’s all very secret. Prompted by Lucie, he says he has to protect the lives of the King and all his family, his guests and his property. He tells her the King is away at the moment and there are less guards here because most of them are with him. He says they’re on alert at the Palace at the moment because the King has a new piece of artwork arriving tomorrow. He tells her it’s called the Black Diamond and it could easily be stolen - in fact, there’s been one attempt already. He also admits that it’s not really a diamond even though it looks like one. She asks him if they keep all such valuables in the vault and he confirms that they do whenever the artwork isn’t on display. Just then, the Doctor joins them and Lucie introduces him as Lord Smythe. She claims she “had a turn” while admiring the Palace and explains how the young guard assisted her. The Doctor rebukes her for associating with young men while unescorted so Anders makes his excuses and goes back to his duties. As soon as they’re alone, the Doctor and Lucie burst out laughing. She says she’s been doing her best posh voice for over and hour and her throat is killing her. Fortunately she’s found out what the piece of art is, when it’ll be arriving and where it’s going to be kept.

As Anders returns to his post, he’s approached by Karen who asks him for directions. As he turns to point the way, the Headhunter emerges from her hiding place and knocks him unconscious. They drag his body away and Karen asks why she didn’t just use chloroform. The Headhunter tells her a good whack over the head is easier, more reliable and above all cheaper. Unfortunately there’s no way they’re going to be able to smuggle an unconscious guard up to their hotel room, so they have no choice but to do the next stage of the plan right here…

The Doctor wonders what the Black Diamond could be and what the Headhunter wants with it? Lucie assumes she just wants to flog it, but he doubts it’ll be that simple. Lucie proposes a toast to crime and although the Doctor joins in, he assures her what they’re planning isn’t a crime. She’s far from convinced and says it’s doesn’t matter how much he dresses it up or goes on about the greater good, the fact is they’re still nicking something. He argues that it’s quite possible to be a morally sound thief and uses Robin Hood as an example. They need to get on with the plan so the Doctor suggests they go back to the hotel so he can test some equipment.

The Headhunter hypnotises Anders and gives him a full set of instructions. When they next meet tomorrow, he won’t remember seeing her before but he’ll accept her claim to be Elizabeth of Bohemia, a terribly important aristocrat. He says he’ll obey and Karen wonders why people always say that when they’re hypnotised. The Headhunter explains it’s a default setting on the mind-probe but says you can change the response to anything you want. She demonstrates and Anders responds to her questions with a variety of different phrases, including the words “cream cheese”. She orders Anders to stay here for two minutes, then return to the Palace and forget that he spoke to them until she uses the trigger phrase ’Elvis Presley’. Karen wonders why she chose that name and the Headhunter says Elvis won‘t be born for another 37 years so there’s no chance anyone else will say it accidentally.

In their hotel room, the Doctor asks Lucie to help him with an experiment. He asks her to pick a book up and walk towards him while looking straight ahead. She does what he says and when he flicks a switch on the machine he‘s built, the book in her hand completely disappears. He explains that he’s built a feedback loop which fed her brain a false impression of what’s around her. The room continued to look the same, so she didn’t notice when he stepped in front of her and took the book from her hands. Unfortunately it only has a short range so he’s going to have to get close to the guards before he can use it. However, her little act with the guard has given him an idea…

Simonsson checks with Henrik to make sure everything is going well and is told there’s a young lady waiting to see him who says she has something to sell. Simonsson agrees to meet her and goes outside where the item is being kept on the back of her carriage. The young woman is none other than Lucie, in her guise as Ms Palmer-Tomkinson. She says she’s just received word that her father is ill and she’ll be returning to England shortly, but before she leaves she wants to offer him the chance to purchase an item that she believes will be of interest to him. The TARDIS is unloaded from the back and Simonsson examines it curiously, wondering whether it’s supposed to have some historical significance. Lucie tells him that it’s main point of interest is inside, so she opens the door and invites him to enter.

Simonsson is amazed by the remarkable scale of the TARDIS interior. He assumes it’s some form of optical illusion, but Lucie says she doesn’t understand how it works so she brought it to him as she’s heard the King is a keen patron of the sciences. She says her family acquired it some time ago but they don’t know where it came from and they’re keen to pass it on to someone who might want to look into it. Simonsson is convinced the King will be delighted with such an acquisition and he invites Lucie to the library to discuss a price. Lucie says she’s concerned about leaving it outside and asks if he’d mind putting it into the vault. Simonsson agrees immediately.

Moments later, another carriage draws up outside the Palace. The Headhunter tells the guard that the King is expecting her, but when he tells her the King isn’t at home she becomes outraged. She claims to have received a letter from the King himself inviting her to enjoy his hospitality while they discuss his support for the tripartite monarchy of Bohemia. She launches into a well-rehearsed “don’t you know who I am?” routine and announces herself as Elizabeth of Bohemia, then she insists on waiting for the King to return and orders the guard to carry her bags inside.

Using a two-way walkie-talkie system, Lucie contacts the Doctor and confirms that Simonsson bought her story and they’re bringing the TARDIS down to the vaults now. He’s watching events on the scanner and reassures her that he’s locked the door again to stop anyone popping their head inside and seeing him. She wonders whether he’s going to have time to grab all the artworks and the Doctor says he probably won’t be able to do much with the statue as it’s about 12-feet tall, so he’ll have to materialise the TARDIS around it. He plans to take the paintings straight away and says they may have to come back for the statue later.

Using a two-way walkie-talkie system, the Headhunter contacts Karen and asks where she is. She’s horrified to learn Karen has gone up to the roof as that’s hardly the quickest way to get to the cellar, but Karen says there are too many guards on the ground floor. In any case, Karen is confident she knows what she’s doing and says she’s seen the schematics (even if they were back-to-front and upside-down) and she’s sure she can get down to the cellar first.

Lucie says she’s delighted with Simonsson’s generous financial offer, but he says it’s just a fair price for a wholly unique item. There’s a knock at the door and Anders enters to confirm that Lucie’s item has now been safely stored in the vault and to alert Simonsson to a “small situation” that’s developed. He says they have another visitor, Elizabeth of Bohemia, who’s come to discuss a political matter with the King. Although the King won’t be returning until Monday afternoon, she insisted on waiting for him, but Simonsson says that’s not possible so he agrees to go and talk to her. Lucie accompanies him but when they get to the library, she’s surprised to see it’s the Headhunter. Simonsson is delighted to see that the two women know each other, but Lucie immediately makes her excuses and leaves, which makes Simonsson think there must be some acrimony between them. The Headhunter warns him against associating with ’Ms Palmer-Tomkinson’ and says her family are of lower quality than they claim. Simonsson is concerned and says he has no wish to stain the King’s name by associating him with someone inappropriate.

Anders and Henrik supervise the safe-keeping of the Black Diamond as it arrives at the Palace. Anders insists on changing the case where it’s to be stored in case anyone witnessed its arrival. If they try to break into the vault and steal it now, they’ll take the wrong item.

Lucie calls the Doctor again and warns him that the Headhunter is already inside the Palace. When he learns that she’s posing as some posh bird from Europe, he guesses she’s playing a long game, which gives them the advantage because he’s already got the paintings and is just waiting for the guards to arrive with the diamond. His feedback loop gadget is ready so he reminds her to switch her neuristor on so she won’t be affected herself.

As the guards arrive in the vault, Anders tells Henrik there are plans to install a permanent detail at Drottningholm and he plans to ask if he can be transferred here. He’s looking forward to the fresh air, the wide open spaces and the fact that he won’t have tourists gawping at him while he’s trying to do his job. They stop suddenly when they hear a noise. They can’t see anything, but when they check the diamond, they discover it’s gone. They assume they must have dropped it on the way down, so they start to retrace their steps, only to bump into Lucie on her way down. She gives them the slip and races off…

Lucie reaches the TARDIS and joins the Doctor inside. He feels sorry for the fact that the guards will probably get blamed for the loss of the diamond and says he’ll think of a way to compensate them. When they open the case they’re disappointed as the Black Diamond isn’t as impressive as they expected and it’s not Tardelli’s usual style at all. He warns Lucie not to look into it too much as it may have unusual properties, but when he tests its resonance with the sonic screwdriver, he discovers it’s made of celluloid. He realises this isn’t the real diamond at all, but the decoy that Karen stole from the train. The question is, how did it get here and where’s the real one?

Karen makes her way down to the vault and calls to Anders. He demands to know how she got down here, but then she says the words ’Elvis Presley’ and he goes into a trance. He confirms that he’d already switched the fake diamond for the real one, as per her instructions. She then collects the real diamond from him and orders him to escort her outside as if she’s his prisoner - but before they can leave they hear a strange noise heading in their direction. Incredibly, the huge statue has come to life and is now striding towards them, so they decide to run for it.

Inside the TARDIS, the Doctor operates the scanner and is shocked to see the statue walking out of the vault of its own accord. However, they’ll have to deal with it later as their priority is to find the Headhunter and Karen. The Doctor programmes the TARDIS to land in the main hall…

Karen and Anders are confident they’ve shaken off the statue, but just as they reach the main hall, the TARDIS materialises in front of them. The Doctor and Lucie emerge and demand that Karen hand over the diamond, but she refuses and orders Anders to hold them off while she gets away. The guard obeys and the Doctor realises he must have been hypnotised. Anders draws a sword and orders the Doctor to surrender, so the Doctor finds another sword from a display on the wall and the two begin to fight. While this is going on, the Doctor tells Lucie to go after Karen who’s probably heading for the south exit.

The Headhunter tells Simonsson she’s most displeased with the situation and he promises to send an envoy to the King tonight to inform him. Suddenly Karen races into the library, closely followed by the statue. In a deep, growling voice, the statue demands that she give him back the diamond she stole. It grabs hold of her and the Headhunter calls for Karen to throw her the diamond, promising to help her later. Karen throws it, but not very well and it falls on the floor some way from the Headhunter. Lucie storms into the library, sweeps up the diamond before anyone else can get to it, then races out again, taunting her rivals. The Headhunter turns her attention to the statue and realises it’s a simple silicate-based creature. She shoots it with a laser and the statue comes to a halt. Karen wonders why she didn’t do that earlier and the Headhunter claims, rather weakly, that she didn’t want to risk hitting her. Simonsson demands to know what’s going on, but the Headhunter can’t be bothered with explanations so she hits him and knocks him out.

As Lucie races out of the building, a carriage pulls up by the entrance. She offers to pay the driver whatever he wants to take her away, but the man reveals that he’s working for the Headhunter and he’s already been paid a little extra to stop anyone escaping with the diamond. The Headhunter and Karen join them and compliment the driver, then the Headhunter draws her weapon and orders Lucie to get inside the carriage. With their hostage safely aboard, she then gives instructions for the driver to take them to the station.

As Simonsson comes round, he tells Henrik that ’Elizabeth of Bohemia’ and the two young ladies must all be accomplices in the same crime. The Doctor is escorted into the library under guard and he apologises for everything that’s happened. Simonsson asks where his accomplices are heading and it soon becomes clear that the Doctor and Lucie were working in competition against the other two ladies to steal the diamond. The Doctor decides to tell the guards the truth and leave it up to them whether they want to believe him. He says the diamond is dangerous because the works of Claudio Tardelli alter the fabric of the world around them and have a malign influence on people. Simonsson argues that he’s been studying the works for years, but the Doctor says he’s had mercifully brief exposure to the genuine works as they’ve never been kept on public display. Simonsson is forced to concede that he saw the statue walk away. Henrik can’t believe what his boss is telling him, but then the statue starts moving again! Simonsson backs away and explains that the woman was able to stop the statue with a gun that spat light and the Doctor realises it must be a silicon based life form, which means the Headhunter’s weapon must have temporarily scrambled its neural pathways. Simonsson is starting to believe what the Doctor has told him and as he needs to get the diamond back quickly, he asks the Doctor if he’s willing to help him. The Doctor agrees and says if they’re lucky, the thieves will be using conventional means to leave the city. However, he has a quicker form of transport…

The Headhunter opens the door of the train compartment and climbs aboard with Karen and Lucie. The train is due to leave in ten minutes for Russia. Lucie says she’s never been there before but the Headhunter says she still hasn’t decided whether to take her along yet and she’s only keeping her close in case the Doctor catches up with them. Karen assures Lucie they’re not evil and that this has all been about business. The Headhunter had been meaning to take on a PA for some time and her meeting with Karen was well timed since she’d just lost her job and discovered her whole life had been fabricated anyway. Karen is angry that Lucie left her for dead during the Cyberman attack and says she was rescued and patched up by the Headhunter. Lucie swears that she did come back for her, but couldn’t find her and everyone else in the corridor was dead. Lucie thinks business must be slow if the Headhunter has resorted to stealing jewels, but the Headhunter assures her there’s a purpose to this crime. She opens the box containing the Black Diamond and urges it to “come out”. There’s a sudden flash of light and then an elderly Italian-looking man is miraculously sitting in the compartment with them. He looks around in confusion and asks why he’s been summoned and the Headhunter says she’s here to offer him a job. Lucie asks who the strange man is and after checking that he’s still on Earth, he introduces himself as Claudio Tardelli.

The TARDIS materialises at the railway station and the Doctor emerges, followed by Simonsson, Henrik and several of the guards. There’s no time for them to be awed by their experience, so Simonsson sends Henrik to find the station manager and tell him to stop all departures as the King’s property has been stolen. Everyone else is ordered to search the station and start issuing descriptions of the culprits.

Lucie is shocked to learn that Tardelli was inside the diamond all the time. He explains that it’s bigger on the inside than the outside and he’s been in there since the 17th century. He fashioned the diamond as an emergency bolt-hole and he used it when his situation in Florence became untenable. He says it’s a masterpiece of compression and contains a small self-sustaining Universe a little under three light-years across. He designed it himself and rules over it, but he says it does get a bit dull after a while if you’re only talking to people you created yourself, so he was thinking of returning to reality fairly soon anyway. He admits that he’s an alien from the planet Parrimor, but he was exiled to Earth by his people. The Headhunter says she’s pleased to announce that his exile is over and he’s now free to leave the planet. Tardelli asks what happened to the Guardian he created to watch over the diamond and the Headhunter realises he’s referring to the statue. She apologises and tells him she shot it, but he doesn’t seem particularly bothered. She tells him the Emperor Vassilar-G of Ralta wishes to employ Tardelli’s services as official court artist in return for very substantial territories, but regardless of whether he accepts the offer, he won’t be able to return to the diamond as she’s planning to sell it to a Russian gentleman named Yashin. She says Yashin is keen to stay ahead of his industrial competitors and plans to collapse the Universe and convert it into enough energy to keep him going as long as he likes, which is a shame as he’s going to be murdered by his own workers in 1905 before he gets to see the benefits. Lucie asks what will happen to all the people in the small Universe, but Tardelli says he made them so he can decide their fate. He agrees to the Headhunter’s plan in return for a share of the proceeds. Karen spots some of the guards searching the station and warns that they’re about to be caught, but the Headhunter had predicted this possibility and has already hypnotised the train driver to pull away at the first sign of trouble.

Henrik calls over to Simonsson and points to the train which the culprits were seen boarding earlier. The train starts to pull out, so the Doctor and the others race to board it before it’s too late. Simonsson is sure they’ll never catch it, but the Doctor remembers it has a top speed of 65 kilometres an hour and it’ll take about 15 minutes to accelerate to that. He leaps aboard and then extends a hand to help Simonsson up too. Simonsson points out that he could easily have left him on the platform and got away, but the Doctor admits the thought never occurred to him. Anders and Henrik are left behind and they can’t telegraph ahead to the next station because communications are down. Henrik suspects that isn’t just bad luck. Just then they hear a commotion as passengers on the concourse start screaming…and then the terrific shape of the statue arrives and strides off towards the departing train…

Karen tells the Headhunter that the Doctor and Simonsson have managed to board the train - and Tardelli reacts to the Doctor’s name with alarm. Karen wonders why they didn’t just use their ship, but the Headhunter tells her you can’t transport matter under this kind of pressure so close to an ion-jet engine. Tardelli agrees and says the competing pressures could cause a serious fracture. The Heahdunter tells Karen to get ready to shoot Lucie if the others give them any trouble and, to Lucie’s alarm, Karen agrees readily.

The Doctor and Simonsson make their way quickly through the crowded compartments, apologising to the other passengers as they get pushed aside. The train guard had pointed them in the opposite direction, but the Doctor realised he’d been gotten to and was probably hypnoptised. Using his sonic screwdriver, he opens the carriage door and finds the Headhunter, Karen, Lucie and Tardelli waiting for him - and Karen has a gun pointed straight at Lucie’s head. Tardelli is surprised to see the Doctor and comments that he looks different from the last occasion they met. The Doctor confirms to Simonsson that this is the genuine Tardelli, but he isn’t human and everything he’d said about the artist is true. Lucie tells them there’s a whole Universe inside the diamond and the Headhunter plans to sell it to someone who’s going to break it down for fuel. Simonsson is shocked to learn there’s an entire realm inside there and Tardelli confirms that it’s populated by people of his own making. Simonsson can’t believe the man he admires so much would create life and then destroy it so easily.

The Headhunter orders the Doctor to back off, but before anyone can react, they all hear the heavy footsteps on the roof above them. Suddenly the entire ceiling caves in as a mighty stone fist smashes through and a deep, growling voice demands that they hand over the diamond. Tardelli isn’t surprised to see his Guardian again and tells it to stand down as he’s quite safe. The Doctor says it must have homed in on the diamond, but Lucie has realised that its orders are to protect the diamond, not Tardelli himself. The Doctor picks up on this and tells the Guardian that Tardelli is perfectly safe, but these people are planning to destroy the diamond and everyone inside it. He asks it what’s more important - the diamond, which he’s pledged to protect, or its creator? The Guardian again demands that they hand over the diamond, but the Headhunter refuses and Karen shoots it with her laser. This time it has no effect and Tardelli explains that it was designed to learn and adapt to attacks. The Headhunter pushes everyone aside and flees, but when Karen tries to follow her, Lucie overpowers her and takes the weapon. The Doctor asks Simonsson to keep Karen and Tardelli covered with the gun while he and Lucie chase after the Headhunter.

The Headhunter charges through the train, once again barging aside any passengers or staff who get in her way. The Doctor appears at the end of the carriage and calls out for someone to stop her as she’s stolen the property of the King. The statue smashes another hole in the roof at the other end of the carriage and a gigantic stone hand reaches down inside. The Headhunter is trapped between the statue and the Doctor and Lucie. The furious woman orders Lucie to get out of her way and says she’s been trained in the defensive arts, but before she can complete her sentence, Lucie kicks out and knocks the diamond from her grasp. As the Doctor picks it up, the Headhunter make a rude remark about Lucie being the Doctor’s ‘dog’, so Lucie follows up her earlier kick with a series of well-timed punches to the woman’s face. The Doctor stops her, then he tells the Guardian that if he wants to protect the people in the diamond, the best thing he can do is set them free.

Tardelli and Simonsson are engaged in a conversation about art and Tardelli is curious to know which of his works are currently in the King’s collection. He’s impressed by Simonsson’s portfolio and he realises that through photographic reproduction he could have achieved his results ten times as quickly if he’d been exiled in this century . The Doctor returns and points out that his work may not have had the same power if they were simply reproductions rather than crafted by him personally. He doesn’t have time to discuss the matter further and tells Tardelli to do something about his diamond. He’s come to an agreement with the Guardian that the inhabitants of the small Universe should be freed, so he persuaded the Guardian to fracture it. It’s only a matter of time now before it spills out into our Universe, causing a collision of matter that will certainly kill everyone. What the Doctor has done is force Tardelli to make an emergency fifth-dimensional dump, sending the little pocket Universe into the gap between Universes where it’ll be able to exist independently. The Guardian has already confirmed that any decent dimensional engineer has the means of dumping his experiments somewhere safe as a last resort. Once the pocket Universe moves outside the container, it will be outside his control too, which is exactly what the Doctor wants.

Tardelli agrees to do it and says it’s of little concern to him as he didn’t want his world to continue anyway. Simonsson is devastated at Tardelli’s response and says he isn’t the man he wanted him to be. Tardelli dismisses his concerns and says the fault is entirely Simonsson’s, not his. He completes his work on the diamond and with a flash it empties itself of the pocket Universe. He hands the diamond to Simonsson as a souvenir, but suddenly Karen leaps forward, snatches the gun back and orders no one to move. The Doctor argues that it wouldn’t do her any good to shoot them now and Tardelli reminds her that the Headhunter is still due to take him to his new job as court artist to the Emperor Vassilar-G of Ralta. Karen agrees to let Tardelli leave with her, so she forces the others to back away and they slip out of the compartment.

Lucie has tied the Headhunter’s hands and is forcing her back down the carriage. As Lucie opens the door at the end, she finds herself facing Karen and Tardelli. He reveals that the Doctor forced him to release the contents of the diamond and the Headhunter is horrified at the thought of Yashin finding out. He’ll have her head for this, which means she’ll never be able to visit Earth again between now and 1905. This strikes her as the ideal time to get off the train and then they can find a secluded clearing where she can summon her warp-ship. She says goodbye to Lucie, then she, Karen and Tardelli leave.

The Doctor sympathises with Simonsson and tells him people should never meet their heroes. The collector agrees and says great artists are not necessarily the best of men. He asks about the two paintings he acquired earlier and the Doctor says they’re currently inside the TARDIS. Simonsson urges him to destroy them while he thinks of some excuse to tell the King, but the Doctor is starting to have second thoughts. He’s already destroyed all the other artworks he found, but he thinks he might have been wrong to do that because all it’s done is make the remaining paintings more valuable and desirable. Instead, he’s going to find out how they work and see if there’s a way of nullifying their effect. Perhaps they could even be displayed in a context that would strip them of their power and let people see them for what they really are. The Guardian taps gently on the train window and the Doctor greets the statue warmly and tells him he’s now free from all his obligations. The Guardian doesn’t know what to do next and Simonsson suggests there are legends of stone trolls in the woods around Stockholm, so he might find some company there.