The Doctor takes Peri to watch Cleopatra’s rehearsal for her entry to Tarsus, but refuses to let her observe the real thing if she insists upon taking her camera; such a dangerous anachronism could change history beyond recognition. They return to the TARDIS and depart, but are assaulted by an alien force with orders to copy whatever it sees -- a force which misunderstands its orders and copies far too much. The TARDIS is caught up in the resulting energy flux tube and transported through the Vortex, a process which drains power from the ship and suspends Peri and the Doctor in Time. When they finally materialise, although only seconds seem to have passed for them, years have passed by in the world outside. Wherever they are, their link to the Eye of Harmony has been severed, and the TARDIS thus has no way to repair its power loss. The Doctor and Peri emerge to investigate, and find that they have arrived in Cleopatra’s tomb -- but the friezes on the walls depict a version of history in which Antony and Cleopatra won the battle of Actium with the use of steam-powered ships. When the Doctor breaks out of the tomb onto its roof, he finds that it is located in Ancient Rome, a city now dotted with street lights, power lines and radio antennae…
Before the Doctor can begin to investigate, Peri discovers feathers growing out of her skin, and the Doctor collapses and regresses to his fifth incarnation. Peri drags him back into the TARDIS, where he returns to normal; however, it is clear that whatever force has severed the link to the Eye of Harmony has also destabilised their morphic prints. The Doctor’s body is regressing through his previous incarnations in search of a stable point, while Peri’s traumatic memories of her near-transformation into a bird-woman on Varos have been given form once again. The TARDIS doesn’t have enough power to operate the morphic stabilisers yet, and the Doctor cannot venture outside without collapsing; therefore, Peri has no choice but to go out and attach solar power collectors to the outside of the tomb. Her brief exposure to the outside world causes her to transform further, however, to such a degree that she will be unable to pass for an ordinary woman. She thus must remain in the TARDIS while the Doctor investigates, and until he can locate the source of the changes, she will remain half-woman, half-bird.
Rome and Alexandria now belong to a Dominion ruled by a triumverate of Antony and Cleopatra’s three children. The two youngest, Alexander Helios and Cleopatra Selene, are scheming to acquire ultimate power, and the eldest, Ptolemy Caesar, does little to stop them, as he has lost all interest in politics since his failed expedition to investigate the loss of trade to the East. He returned from the expedition shaken and subdued by what he found, while his friend Agricola was driven quite mad by the experience. Alexander and Selene’s rivalry has thus gone unchecked, and has only become more complex as they grow older. Cleopatra’s body is to be sent to Alexandria to lie in state, and Selene is on her way to Rome for the ceremony -- but she knows that Alexander has plans to stop her, and has laid her own counter-plots already. What nobody else knows is that Selene has been kidnapped and replaced by an impostor, who has her own reasons for wanting to get to Rome and its divine Oracle. Alexander, meanwhile, requests that his elder brother approve the use of the weapon code-named “Ultimus” in special circumstances, but again Ptolemy refuses, knowing the dreadful consequences of such a weapon. Alexander is disappointed, but acknowledges that he now has no choice; for his plans to succeed, Ptolemy must be assassinated.
The Doctor ventures into the streets with a miniature camera and a subdermal communications unit so Peri can keep track of his movements. Seeking gossip in the local tavern, he meets a Greek philosopher named Themos, who drunkenly tells him that the world is coming to an end. Themos has calculated the position of the sun and has proven, without a doubt, that since the last time similar experiments were carried out, the sun has drawn nearer to Earth without increasing in its apparent size, which means that it must be shrinking as it draws nearer. Either the sun is going to collide with the Earth, or it is going to go out. The Doctor returns to Themos’ home to study his calculations, and finds that Themos has collected the preserved bodies of gruesome animals from the East which look like nothing from Earth. When he inquires about the rapid technological advances which Roman society has made, Themos puts them all down to the arrival of the Oracle, and the Doctor thus sets off for the Oracle’s temple to investigate.
Peri is forced to emerge from the TARDIS when a party of grave robbers try to break into the tomb and steal its treasures. She uses glow-in-the-dark paste and her own feathered appearance to convince them that she is the spirit of Cleopatra, and the terrified tomb robbers flee straight to the nearest tavern. Peri, pleased with herself, decides to face her fears and remains outside, allowing her transformation to complete itself. To her surprise, once it does so and she becomes a complete half-human half-bird hybrid, she discovers that she has acquired the ability to fly, and feels stronger both in body and in mind. When the Doctor learns what she has done, however, he warns her not to become too accustomed to the change; when it is reversed, she may feel as though she’s lost something. Peri, however, is more concerned with something she saw earlier. Themos claimed that Cleopatra’s body already has been moved out of the tomb in preparation for the move to Alexandria, but Peri has already found the tomb’s inner sanctum, and it does not appear to have been opened.
The Doctor, unable to get close to the Oracle without a research ticket, waits for night to fall and then breaks into the temple. But when he enters the Oracle’s chamber, even he is surprised by what he finds -- an exact copy of his own TARDIS console, down to the scratch where Peri dropped her coffee cup. What’s worse, the console’s telepathic circuits and memory banks are active, and the Romans have been using them to make great leaps forward in their technology -- and are on the verge of learning how to make an atomic bomb. Before he can investigate further, however, Alexander Helios arrives for a private session with the Oracle. The Doctor is forced to fight Alexander’s bodyguards with whatever he can find close to hand, including the religious furnishings of the Oracle’s chambers. Alexander, amused, offers the Doctor the chance to fight for his life against Cleopatra’s bodyguard Gandos, and the Doctor has no choice but to accept.
Since the Doctor is now imprisoned, he has no choice but to send Peri to Rome’s nuclear power plant, to install transducers which will siphon energy from the plant into the TARDIS. As she flies towards the power plant, however, her detector pinpoints another source of radiation, in the chamber where Cleopatra’s body is supposedly being kept. Peri, quick on the uptake, realises that Alexander intends to smuggle an atomic bomb into Alexandria disguised as his mother’s coffin. She plants the transducers on the bomb, intending to render it harmless, but before she can depart Ptolemy Caesar arrives to pay homage to his dead mother. Peri sees two assassins closing in on him, and calls out a warning, saving his life. She takes the wounded Ptolemy back to the TARDIS to recover, and while amazed by his surroundings and by Peri’s appearance, he nevertheless accepts that this strange bird-woman means him no harm. When she tells him what she has discovered, he realises that Alexander has gone against his orders and authorised the use of Ultimus -- and is willing to destroy the entire city of Alexandria just to remove his sister from the triumverate.
Faced with this evidence of his brother’s crimes, Ptolemy finally accepts that he has allowed the horror of his expedition to the East to cloud his judgement, and has failed to curb the excesses of his younger siblings. Speaking with the Doctor via his communicator, Ptolmey tells him and Peri of his expedition and of the half-melted villages and increasingly monstrous creatures they encountered as they progressed. The plants became poisonous, and although the land remained flat the soldiers felt as though they were beginning to struggle up a steep hill. Eventually, only Ptolemy and Agricola were willing to continue, though Ptolemy realised Agricola was terrified and only allowed Agricola to accompany him because he was too frightened to go alone. As they drew closer to what had appeared to be a distant mountain range, they found that it was the ground itself, folded up and torn apart before their eyes -- and on the other side the world ended in a black void populated by monsters even more hideous than those they’d encountered before. Agricola was driven mad with terror, and has never recovered. Ptolemy confirmed that the world was bounded in all directions by the void, and returned to Rome a broken man. This is why he has refused to authorise the use of Ultimus under any circumstances; he knows too well that the world is finite, and that use of the ultimate weapon would destroy them all.
The Doctor realises that he and Peri have arrived in a copy of the real world, and that the outermost regions were blurred by the process of copying, creating monstrous hybrids and half-melted, unfinished villages. Ptolemy accepts that he must take responsibility for his siblings, and as he and Peri ponder how to rally public support for their cause, the tomb robbers return, drunk and fortified with magic talismans. They find Ptolemy waiting for them, and after Peri poses as the eagle spirit of Rome, chastising the tomb robbers for their crime, they are only too willing to pledge themselves whole-heartedly to Ptolemy’s cause. The gang’s leader, Cassadorus, sends his men out to drum up popular support and enlists Themos to take their cause to the learned citizens of Rome. Meanwhile, Alexander, furious to learn that Ptolemy has escaped, orders his trusted servant Vitellius to accuse Ptolemy of treason and send soldiers to search the homes of his friends. Agricola is particularly distressed to learn that Ptolemy is in trouble; he knows distantly that he once ran away from Ptolemy and has vowed never to do so again. Alexander eventually realises that he is stirring up public opinion against himself and orders Vitellius to announce that the orders were misunderstood, but by that time the damage has been done.
Cleopatra Selene arrives in Rome for the festivities, and while dining with her brother she learns of the stranger who sought an unauthorised audience with the Oracle. Claiming to be intrigued, she goes to visit the Doctor in the gladiatorial academy -- and the Doctor recognises her as the Rani in disguise. After their encounter in Luddite England, the Rani was trapped in her own TARDIS when the Master split off its console room from the rest of the ship in order to escape, and while trying to stabilise its orbit within the Vortex she became trapped in a bubble of space-time inhabited by a single, benign entity with the ability to copy anything it observed in the outside Universe. She taught the entity to control its powers and ordered it to track down a TARDIS console and copy it for her -- but the entity misunderstood her instructions, and copied most of Europe and Africa as the Doctor’s TARDIS attempted to dematerialise. The resulting energy drain caused the Doctor, Peri and the Rani to become suspended in Time for several years, during which time the creature taught itself how to maintain its new world’s stability, and set “monsters” in the void to prevent anyone from venturing too far. The Rani took on the form of Selene in order to get close enough to the Oracle to steal it, but the Doctor realises that she too has fallen victim to morphic instability and has taken on many of Selene’s mental characteristics. As such, she intends to conquer this alternate Dominion, and use the people as slaves to further her own ambitions.
Ptolemy needs someone to deliver letters to his supporters, informing them of his plans, and as Alexander has posted sentries throughout Rome, Peri flies through the city and drops the letters through open windows. Agricola catches her delivering a letter to his father, but she manages to convince him that she is a friend of Ptolemy’s, and he agrees not to tell anyone that he has seen her. The Doctor, meanwhile, completes his gladiatorial training and prepares to face Gandos, but a chance remark from another gladiator about his fear of facing a pack of wild animals gives him a thought which he passes on to Ptolemy…
The day of the Games dawns, and much to Alexander and Selene’s surprise, Ptolemy’s arrival is greeted with wild cheers of support from the people. The Doctor faces Gandos down with an unconventional weapon he has had custom-made for the fight. As he suspected, Gandos is not used to fighting an opponent who is not trying to kill him. The Doctor thus wins the fight and knocks Gandos unconscious -- and before Alexander realises what is happening, the Doctor has bowed to Ptolemy, making it appear to the masses that he was Ptolemy’s champion all along. Furious, Alexander publicly declares himself the new Emperor of Rome, and challenges anyone to dispute his claim. Ptolemy thus offers to step into the arena with Alexander to face a pack of wolves, the animals which by legend suckled the founders of Rome; whomsoever the animals choose will become Emperor. Before entering the arena, however, Ptolemy secretly sprinkles himself with a vial of pheromones from the TARDIS storerooms, and the wolves thus ignore him and attack Alexander. But instead of rescuing Alexander, Vitellius reveals that he has been working for Selene all along, and Selene’s troops seize control of the arena, leaving Ptolemy to the mercy of the wolves as the pheromones begin to wear off.
Peri has seen all of this on the Doctor’s communicator, and as she flies out to the arena to create a distraction, Selene’s troops move out into Rome to seize the Oracle. Vitellius had advised against such a move, and as he had predicted, the people of Rome rise up to defend their home against the attacking Egyptians. Cassadorus and his men help to spark a riot in the arena, and when Peri arrives the Doctor and his friends take advantage of the distraction to turn against their captors. In the struggle, the Doctor’s morphic stabiliser is smashed, and he collapses and begins to regress to his previous incarnations. Peri carries him back to the TARDIS, where he begins to stabilise and finds that the TARDIS has now been restored to full power. Peri then returns to the arena, where Agricola has leapt into the ring to help Ptolemy fight off the wolves and Selene’s men. Selene’s troops, however, have overpowered them, killing Agricola and taking Ptolemy prisoner. Vitellius is furious with these changes to the plan, but the Rani now reveals that she is not Selene after all -- and that even the real Selene was just using Vitellius for her own purposes. The Rani injects Vitellius with a poison which transforms him into a potted plant, telling the horrified Ptolemy that, as it seems he is to be the next ruler of Rome, she intends to possess his form.
The Doctor pilots his TARDIS into the Rani’s, where he finds a gateway to the Vortex bubble and meets the creature inside. The Rani has not even bothered to give it a name, and the Doctor thus names it Iam and speaks with it. Iam is delighted when the Doctor actually explains things to it, rather than just giving it orders as the Rani had. Realising that Iam is basically benevolent, the Doctor connects a fibre-optic link to his own TARDIS console and flings it out to Iam, which downloads information from the TARDIS data banks and learns how to create a new planet in an unoccupied solar system in the real Universe, one to which it can transport itself and the entire Dominion and its people. The Doctor then releases the real Selene, whom the Rani had kept alive in her TARDIS in order to maintain her morphic signature link. Peri has just broken into the Rani’s airship and rescued Ptolemy, and as her link to Selene is severed the Rani recovers her wits and realises that her plans have come to nothing. She thus takes the Oracle into her TARDIS, installs it and departs, just as Iam transports the Dominion to its new home on a new Earth orbiting a distant star. Back in the real Universe, Peri becomes human again. The Rani has escaped, but Selene, shaken by her experiences, will not challenge Ptolemy’s bid for leadership. The Doctor and Peri thus depart, secure that the citizens of Terra Nova will have a bright future under a strong leader.
Source: Cameron Dixon