As a historian, Evelyn is infuriated when the Doctor casually suggests that her profession can never reveal the truth; one man’s past is another’s present, and “history” is just a filtered, sanitised story with which people separate themselves from the unforgivable atrocities of the past. The TARDIS then materialises in London, 1903 -- and begins to shudder, as if trying to materialise in two places at once. The Doctor and Evelyn struggle outside to find themselves in the chapel of St John in the Tower of London. Dismissing the turbulence as unimportant, the Doctor resumes his argument, reminding Evelyn that, as they know, the Tower was once a place of torture and execution, but is now nothing more than a tourist attraction. Oddly, however, the chapel is dusty and deserted, as though no one has been here for years. The Doctor tries to fetch a torch from the TARDIS, but it dematerialises without him and he faints, overwhelmed by the sounds of screaming, explosions and very familiar energy weapons. As he passes out he warns Evelyn that they’ve been here before, and are in terrible danger...

Nigel Rochester, the President of the English Empire, is being very naughty and rebellious by speaking in contractions with his wife Miriam. Nigel soon tires of the game, slaps Miriam into submission and orders her to get her beauty sleep for the celebrations tomorrow. Elsewhere, Commander Farrow and a guard named Lamb prepare to torture their famous prisoner; the President wants it to speak at the jubilee tomorrow and has authorised them to do whatever it takes to get it speaking. Lamb activates the cell’s magnetic field, freezing the prisoner in place, and he and Farrow then enter the cell to address it, offering it a chance to save itself pain by speaking to them. It remains silent, and Farrow and Lamb set to work.

The Doctor recovers, but remains disoriented and is unsure what’s happened. He theorises that the TARDIS, which had been trying to materialise in two places at once, has now gone from one to the other -- but where? Evelyn finds a clue on the stained glass window, which depicts a blue box on a green hill, surrounded by flecks of red as if symbolising its arrival in a time of war. The Doctor decides to explore, but cautiously...

The Prime Minister of the Americans speaks to President Rochester to offer the congratulations of the American people on the jubilee. Rochester enjoys watching the PM squirm nervously, obviously terrified of offending him. Miriam enters, claiming she is too excited to sleep, and is condescending and dismissive when she sees the PM on the video link. The Americans may look like the British and speak the same language, but the accent always gives them away. No one who leaves England is ever permitted to return; they must keep the English race pure.

The prisoner still refuses to speak, and Lamb is starting to wonder whether its speech organs have atrophied. Convinced that it’s just being stubborn, Farrow orders Lamb to stand outside, and once alone, Farrow informs the prisoner that there are those who wish to save its life and overthrow President Rochester. If it refuses to help them, then the torture will really begin. The prisoner remains silent, and Farrow thus prepares to slice open its optic nerve...

Evelyn and the Doctor emerge from the Tower to find the grounds festooned with lights, ribbons and bunting, and the Tower itself decorated in a bizarre combination of clashing colours. A metal box has been roughly attached to the side of the Tower, and the Doctor throws caution aside when he hears a terrible electronic screaming from the annex -- the sound of something in terrible agony...

Farrow screams in pain as the prisoner’s flesh grows back over his hand, trapping and burning it. Lamb cuts Farrow free, and Farrow realises that he doesn’t know whether the prisoner was screaming in pain or laughing at him. The Doctor and Evelyn arrive outside, and Lamb leaves the cell to investigate -- and is shocked when the intruders blatantly contract words while demanding to know what’s happening. Farrow emerges as well, and is shocked when the Doctor identifies himself and Evelyn. Unnerved, he reports to President Rochester that an intruder calling himself the Doctor has arrived -- and unlike all of the others, this one is wearing a patchwork coat of many colours. How could he have known?

Rochester orders Farrow to bring the intruders to him, and allows Miriam to stay up and watch the interrogation. When the Doctor enters, Rochester seems overwhelmingly happy to see him and offers the Doctor his leave to take everything in the palace, including his wife -- it’s the least they can do for their saviour. Rochester then drops the act and threatens to kill Evelyn unless the intruder tells him how he learned the truth about the Doctor’s coat. In all of the official histories, the Doctor is depicted as wearing something far more suitable than this outlandish coat -- and when the impostors show up, they are invariably dressed like the Doctor from the movies. So how did this intruder know the truth?

Despite the Dalek’s threats, nothing further happens, and the Doctor realises that its gun has been removed -- and its casing cracked open. Outside, Rochester realises that this really is the Doctor, and has no choice but to release him. Mindful of the danger, the Doctor insists that the Dalek be destroyed at once, and is only a little mollified when Rochester assures him that it is to be blown up at noon tomorrow. The Doctor and Evelyn follow Rochester, Miriam and Lamb back to Rochester’s rooms, while Farrow switches on the magnetic field and confronts the Dalek, furious now that it’s proven it can talk after all. He promises to restore the Dalek’s freedom if it teaches him what he needs to know about power -- but the Dalek isn’t interested in freedom. It wants the Doctor brought back, and then it will teach Farrow all about power.

Rochester assures the Doctor that only two Daleks survived the invasion 100 years ago, and that the other was killed for the 50th anniversary. Now that the Doctor has proven his identity, Rochester and Miriam seem overjoyed to have him and Evelyn back, for they’re the ones who led the English into battle 100 years ago, destroying the Daleks and paving the way for a better world. The Doctor feels faint, hearing the echoes of battle in his mind, but he pulls himself together and accepts a drink offered by Rochester -- until he learns that the drink is “Dalek juice,” a fluid excreted by the Dalek when its body is boiled. Dalek juice is considered a specialty, but Miriam admits that any ordinary drink with a picture of a Dalek on it will sell millions. Evelyn is appalled to learn that the thoroughly evil Daleks have been trivialised to for use as merchandising tools, but the Doctor realises that it’s more than that -- they’re also being used to “educate” the people of England about their own superiority.

Miriam mentions that the Dalek prisoner, as bad as it is, isn’t as awful as the wheelchair-bound prisoner in the Bloody Tower -- but Rochester hushes her at once, despite the Doctor’s curiosity. According to law all women must be in bed before midnight, and the Doctor offers to show Evelyn to her room before speaking with Rochester further. As Lamb leads the Doctor and Evelyn to the guest quarters, Miriam ostentatiously yawns and prepares to withdraw as well -- but Rochester suspiciously notes that she seems to be behaving just a little too stupidly. She’d better be careful not to prove his suspicions legitimate...

Lamb shows Evelyn to her room and withdraws, awe-struck by the return of such great heroes but unwilling to admit what’s really happening here. Evelyn is appalled by what she’s seen, but the Doctor feels this proves his point; history is written by the winners, and the losers are mocked and belittled. As far as the time paradox is concerned, the Doctor suspects that he and Evelyn did land in 1903, but changed the course of history so catastrophically that time itself was fractured. When the TARDIS tried to materialise, it fell down the crack in time, and now both past and present are meshing together -- and somewhere there are Daleks, which can only make the situation worse. Evelyn offers to question the Dalek, but the Doctor flatly refuses; even without a gun it can still get inside her head. Instead, he urges her to stay where it’s safe while he talks to Rochester. She agrees to do so -- but as soon as the coast is clear, she slips back out, determined to find out the truth on her own.

Rochester gives the Doctor a tour of the Tower’s museum, which is full of alien technology the Doctor knows should never have been allowed to survive. On the roof, Rochester shows off the last surviving transolar disc, and offers to take the Doctor on a bird’s-eye view of London in celebration. As they clear the Tower, the Doctor sees that the rest of London lies in ruins -- and Rochester admits that this was done not by the Daleks but by his own father, who wanted to build a glittering new capital city from scratch but lost interest. Rochester has no interest in rebuilding the ruined city; he’d rather give his people a glittering Jubilee celebration with a big extermination as its centrepiece than bother with the fiddly details of architecture and reconstruction...

Lost in the corridors of the Tower, Evelyn walks into a room to find herself surrounded by Daleks -- who ask if she’d like to play with them. Miriam arrives and sends them off duty, explaining that these are her husband’s toys. Evelyn asks permission to see the real Dalek, and Miriam agrees to help her break the rules and takes her to the cell. There, Farrow lets Evelyn in, but is furious with Miriam for failing to bring the Doctor. Nevertheless, she slaps him when he uses a contraction in front of her; she will not accept that kind of insolence...

Evelyn speaks to the Dalek, who soon realises that she fears it even though it can’t physically harm her. Since the Doctor sends his friends into battle against the Daleks, and they obey his orders willingly, the Dalek regards them as enemy soldiers who obey their commanding officer -- and thus, seems to regard Evelyn as its equal. It refuses to answer her questions unless she turns off the magnetic field and lets them talk as equals, and although reluctantly, she does so. The Dalek knows that she will not ask it the same questions as all of its other visitors, who just want to know how they can conquer as effectively as the Daleks do. Evelyn comes to understand that this Dalek is just an ordinary soldier, and simply obeys orders -- that it has no idea why the Daleks do what they do. It was sent to the front lines with orders to conquer or die in the attempt, but when it was captured the humans disabled its self-destruct unit. It has been kept alive for 100 years, unable to kill and unable to die. Farrow calls an end to the interview, and Evelyn realises that he’s going to torture the Dalek once more -- because those are his orders. Sadly, she bids the Dalek goodbye and leaves. Farrow is enraged that the Dalek didn’t even attempt to kill her, but the Dalek simply repeats its instructions -- it wants the Doctor brought to it, and that’s all it wants.

Rochester brings the disc in to land, and due to the curfew, there’s nobody around to see when he pulls a gun and orders the Doctor to step away from the disc. The Doctor, expecting that Rochester is going to try to kill him, is surprised when Rochester instead shoots and destroys the disc, claiming that it was bugged. Rochester believes that there are Daleks everywhere, and that everyone but him is under their control. He leads the Doctor to Trafalgar Square, explaining that the people of Britain secretly understand that the Daleks are their superiors, and that they would never have been defeated if not for the Doctor. The Doctor is appalled to see that Nelson’s Column has been replaced by an image of the Doctor himself -- but a Doctor with bulging muscles, dressed in the uniform of an English Empire stormtrooper.

This is the Doctor who defeated the Daleks in 1903, and the people of England repaid him by cutting off his legs. But that’s his own fault for trying to escape when they told him not to, not to mention rescuing them from the Daleks and thus forcing them to make their own decisions rather than being allowed to obey orders. Now all he can do is dream of travelling through time and space, and reminisce fondly about his friend Evelyn, who died here in the Tower years ago. Realising that the imprisoned Doctor is beyond help, all Evelyn can do is assure him that she forgives him for letting her die, and leave him to his madness. Miriam explains to the horrified Evelyn that the English government refused to let the Doctor leave after the Daleks were defeated, as they realised they could do anything if the public believed the Doctor was on their side. For propaganda purposes, the Daleks and the Doctor are two sides of the same coin -- the ultimate bogeymen and the ultimate hero, with the threat of one and the promise of the other keeping the public in line. Miriam insists that the Doctor and the Dalek must be shown to the people for what they truly are, and Evelyn agrees to help her do so.

In Trafalgar Square, the Doctor is finally beginning to understand the devastation he caused in 1903. In his version of history, the political tensions and imperial ambitions of the European countries led to the First World War -- but in this version of history, the English got their hands on Dalek technology and conquered the entire world. Rochester insists that he’s trying to change all that, but claims that he’s the only one in the world who can resist the Daleks’ mind control; thus, although he desperately wants to be a good man, he must pretend to be evil and ruthless, and order the execution and imprisonment of dissidents so the others won’t report him to the Daleks. The Doctor does understand, perhaps more than Rochester realises.

Evelyn returns to the Dalek’s cell, and tries to explain that Miriam and Farrow want it to tell the crowd what’s been done to it in the name of the English Empire. But to Evelyn’s shock, Miriam admits that, in fact, they want the Dalek to exterminate Rochester and his supporters. Evelyn flatly refuses to be a part of this -- and so does the Dalek, who doesn’t care whether it lives or dies, and sees no purpose in exchanging one human ruler for another. Miriam orders Farrow to kill Evelyn unless the Dalek agrees to help them, and to Evelyn’s surprise, the Dalek agrees to the alliance in order to save her life. Satisfied, Miriam orders Farrow to have Lamb fit the Dalek with a gun, and takes the shaken Evelyn to prepare for the Jubilee.

The Doctor and Rochester return to the Tower as dawn breaks, the curfew is lifted, and people fill the streets, celebrating the Jubilee. But amidst the roar of the crowd the Doctor hears familiar sounds of battle, and Rochester is horrified when a squadron of Daleks on transolar discs flies over the Thames and opens fire on the crowd. The Doctor refuses to accept their presence as reality; the Daleks were defeated in 1903 and must not be allowed to return. He recovers, shaken, to find that Rochester no longer recalls seeing the Daleks, if they were ever there. But a man in the crowd has dropped dead, not of a heart attack, but because he’s been shot by a projected energy weapon. The Doctor realises that the Daleks are returning, and he can’t stop it from happening...

Lamb believes that the gun he’s fitting in the Dalek casing is for show, to please the crowd at the jubilee celebrations -- but when he’s finished, Farrow switches off the magnetic field and orders the Dalek to test its new weapon by killing Lamb. Instead, the Dalek turns its gun on Farrow and orders him to kill Lamb himself, so the Dalek knows whether Farrow has it in him to kill. Farrow tries to stab Lamb to death but finds that he can’t bring himself to do it; he has had people killed by others, but has never killed anyone himself. The Dalek thus orders Lamb to kill Farrow, and the furious Lamb shoots Farrow without hesitation. Farrow has learned his lesson -- power is the ability to do yourself what you want others to do.

The Dalek orders Lamb to take it to the Doctor, and Lamb takes it to the imprisoned Doctor in the Bloody Tower. There, the Dalek dismisses Lamb... and asks the Doctor to give it orders. As Evelyn had realised, this is just an ordinary Dalek soldier, and it knows only how to obey orders, not how to decide things for itself. Only the Doctor understands this, and only he can tell it what to do. The Doctor bursts out laughing and refuses to give the Dalek any orders, and the enraged Dalek exterminates him. Terrified, Lamb takes the Dalek back to its cell -- on its orders. All it can do now is wait to see what will happen at the Jubilee.

Miriam applies makeup to the petrified Evelyn, explaining that she never wanted to put an end to the cruel English Empire after all; she just wants to replace her weak-willed husband with a strong leader who knows how to oppress the weaker species properly, and who actually hits her hard enough to break the skin. When Farrow fails to report in, Evelyn offers to go find him, leaving Miriam to make herself up for the Jubilee. Evelyn finds Farrow dying, and when Lamb and the Dalek return, she demands to know why the Dalek doesn’t just kill her as well. It doesn’t know, and is confused and upset by the question -- but admits that she is the only one who fears it as she is supposed to. Farrow dies, and the Dalek orders Lamb to cut off his head, as is traditionally done to traitors at the Tower. Lamb takes Farrow’s head to Miriam, who is slightly peeved by his death and invites Lamb to become her new consort. Terrified, he turns her down, insisting that he’s only good at obeying orders. Miriam thus dismisses him and gets back to preparing for the Jubilee.

The Doctor and Rochester return to the palace, where Rochester gleefully shows the Doctor the toy Daleks which Evelyn stumbled across earlier. The toys wheel about, chanting and singing songs, as Rochester explains that he plays with them and pretends to fight them heroically just as his great-grandfather did 100 years ago. The Doctor is even more appalled when Rochester reveals that these are not robots; he’s ordered the other rulers of the world to send him their dwarves. Another dwarf has just arrived from America, but he’s a bit too large to fit inside the casing -- and before the Doctor can stop him, Rochester cuts off the dwarf’s hand so he’ll fit inside, all the time insisting to the Doctor that he’s only pretending to be evil. The horrified Doctor tries to explain to Rochester that if he really wants to be a good man he has to make the choice to behave that way, but talking reason to a madman proves ineffective, and Rochester simply fetches Miriam and prepares to attend the jubilee celebrations with the Doctor and the Dalek by his side.

A crowd of cheering Englishmen attends the Jubilee celebrations, and Rochester stands before them with the Dalek prisoner by his side. One hundred years ago, the English won a war against evil monsters who wanted to exterminate them all, and now they will destroy the last of them. Rochester orders the Dalek to speak to the crowds, but it refuses to do so. Terrified that the crowd will see this as a failure on his part, and learning that the Dalek has only ever spoken to Evelyn, Rochester threatens to kill her unless she gets the Dalek to speak -- and it does so, saving her life once more. As ordered, it threatens the crowd with extermination, and the crowd applauds, as the Dalek is finally behaving just as they expected it to.

Rochester then turns the microphone over to the legendary Doctor, who tells the crowd that, as the President wishes, he is going to tell them about evil. But he’s going to tell them about true evil, not the sanitised version they’re here to celebrate. The Daleks were genetically engineered to hate all other forms of life -- but human beings have a choice, and what they’ve chosen to become is appalling. The Doctor no longer cares whether they kill the Dalek or the Dalek kills them; there’s no longer any difference between them.

Miriam takes the opportunity to denounce her husband’s evil regime, and orders the Dalek to exterminate him. The Dalek refuses to do so, but the panic-stricken Rochester flees, shooting wildly to cover his retreat. Miriam announces that she has successfully deposed her husband -- and proposes to the bewildered Dalek, offering to marry it and thus provide the English Empire with the strong leader it requires. Lamb points out that the crowd came here for an execution, and Miriam thus offers the Doctor and Evelyn as sacrificial victims in the Dalek’s place. The crowd chants enthusiastically -- “Exterminate! Exterminate!” -- and the Doctor collapses, no longer able to hold back the pressure of the timelines. Familiar figures appear in the crowd and the TARDIS appears on the nearby hilltop as 1903 and 2003 overlap. The crowd want there to be Daleks in the world, and thus 2003 becomes 1903 and the Dalek invasion force materialises in the crowd, exterminating every human they encounter.

Lamb drags the protesting Miriam to safety as a Dalek saucer swoops down, bringing the Dalek Supreme to investigate the presence of the Dalek prisoner. The Dalek Supreme identifies the Doctor but dismisses Evelyn as no importance -- but the prisoner intervenes to save her life once more, although even it doesn’t understand why. The Dalek Supreme orders that the Doctor, Evelyn, and the prisoner be taken to the mothership for interrogation.

Lamb abandons the struggling Miriam and flees, but Rochester, hiding in the rubble, ushers her to safety. He admits that he’s always loved her, and hopes that perhaps now that he’s a victim rather than a leader at last, they can both be happy. She isn’t sure how to take this, but before she can decide the two are confronted by a Dalek with orders to locate the human leader. Both Rochester and Miriam claim to rule the English Empire, and when the Dalek insists that the true leader step forward, Miriam stabs her husband in the heart and proudly surrenders to the might of the Daleks. Unfortunately, she learns too late that the Dalek’s orders are to find the human leader -- and exterminate her. Elsewhere, the real Daleks find Rochester’s dwarf Daleks dancing about and singing a merry song, and exterminate them without hesitation.

The Doctor, Evelyn, and the Dalek prisoner have been locked up in the Dalek mothership. The prisoner knows it will be exterminated for supplying Dalek technology to the humans, and blames itself for misjudging humanity to be suitable heirs to the Dalek legacy. The Doctor informs it that it’s misjudged not humanity, but the Dalek legacy itself; any empire can expand only so far, and without new worlds to conquer and enemies to exterminate, the conquerors must turn on themselves in the end, inventing new and ludicrous rules to give themselves an underclass to suppress -- whether those rules are based on skin colour, beliefs, or the contracting of words. If the Daleks ever do destroy all other life forms, they’ll have no choice but to turn on each other, until in the end, only one Dalek is left, forever alone, purposeless and insane.

As the prisoner considers what the Doctor has said, it is summoned before the Dalek Supreme to explain why it allowed Evelyn to live. It admits that it has gone mad, and suspects that it has come to respect Evelyn. The Dalek Supreme reminds the prisoner that it is only to respect other Daleks. The prisoner has been allowed to live so it can reveal the reason for their invasion’s defeat, but the Dalek Supreme doesn’t know whether it can be trusted; thus, it orders the prisoner to bring the Doctor and Evelyn here and exterminate them as proof of its loyalty to the Dalek race.

Evelyn remains concerned for the prisoner and is appalled by the Doctor’s callous attitude to its fate. He insists that his history with the Daleks has shown him no Dalek can be trusted, but as far as Evelyn is concerned that only proves his original point -- history is just what one chooses to remember. If he truly believes every Dalek to be exactly the same, then he’s no better than Rochester. The prisoner then arrives and forces them to follow it to the bridge. There, the Dalek Supreme activates the command net so the prisoner can give the Daleks all of the information they need to defeat the people of Earth -- and orders it to kill Evelyn. The prisoner finds that it is unable to exterminate her, and though it offers to exterminate the Doctor instead, the Dalek Supreme refuses to give the order; the prisoner has shown it cannot be trusted, and its information is therefore useless.

The prisoner insists that it has vital information which will ensure the Daleks’ survival, and when the Dalek Supreme refuses to allow it access to the command net, the prisoner exterminates it and connects itself to the command net on its own initiative. It has seen what became of the English Empire, and it has accepted the Doctor’s argument; if the Daleks ever successfully conquer the Universe, this will lead to their corruption and destruction. To succeed, they must fail; to survive, they must die. This data goes directly into the Dalek command net, and every single Dalek in the invasion force obeys the new orders without question -- and self-destructs. Only the prisoner survives, as it has no self-destruct mechanism... and Evelyn is the only one it trusts to do what is necessary. This time, she agrees to remove its gun, and the Dalek does not kill her when she does so. The Doctor stands by sadly as Evelyn fulfils the Dalek prisoner’s last request and exterminates it with its own gun.

The Dalek invasion fleet has been destroyed before invading the Earth; thus, the invasion of 1903 never took place, and the Doctor and Evelyn find themselves standing outside the Tower of London in the year 2003, just as they remember it. A tourist named Nigel Rochester has just collapsed in the crowd, and as his loving wife Miriam panics, the Doctor examines him and finds that he’s had a heart attack -- it’s almost as though he’s been stabbed, though there’s no sign of a wound. The Doctor administers CPR, reviving Rochester, but is appalled when the delirious man recognises him and thanks him for saving them all. As the paramedics take Nigel away, the Doctor and Evelyn retreat to the TARDIS, passing a hawker selling T-shirts with pictures of Anne Boleyn.