It is Christmas Eve, and Donna and her friends are celebrating in a pub. As Donna explains that she has just been promoted in her job she sees that her friend Alice keeps looking at her back, seemingly disturbed by what she sees. The young woman claims there is something perched there but she can’t quite see it…
Before they can talk any more about it a man enters the pub and tells everyone to go outside, a Christmas star has appeared in the sky. They do so and sure enough see the giant silver star hanging in the sky above London. However, when Donna looks at the apparition she notes that it is not a star – it is a web. Suddenly the alien object begins shooting giant bolts of electricity down onto the city, causing chaos. The crowd outside the pub disperses, but Donna remains, with Alice still standing behind her looking worriedly at her back. She claims that there is something there then runs away with the others.
Concerned about what is going on, Donna hurries away to get a better look. As a giant tank pulls into one of the busy streets and blasts the star to oblivion, an army barricade is set up, blocking Donna’s way. She looks on as a stretcher is brought forward, carrying the remains of a body found underneath the Thames. One of the soldiers, speaking on his radio, claims the man was fighting a giant red spider but could not save himself when the chamber he was in beneath the river flooded.
As the stretcher is carried away the body’s arm drops down the side of the trolley, revealing that the man was holding a strange metallic device when he died. As he is carried away into the Ambulance the soldier confirms what has happened – the Doctor is dead, unable to regenerate.
As Donna turns away she meets a blonde woman running toward the scene of the accident. She asks frantically what has happened and Donna explains that a man called the Doctor has been killed. The stranger is distraught by this, claiming she has travelled a great distance to find him, and now he is dead.
She asks Donna her name, but does not reciprocate when posed the same question. Instead she seems intrigued by Donna’s back, just as Alice was. When Donna asks why she is staring at her she claims she is doing nothing of the sort. Donna turns around to try and see for herself what it might be she was staring at and when she turns back, the woman is gone.
Some months later Donna finds herself at work, under threat of being fired. She protests but her employer and her workmates are not concerned, instead they are fascinated when the building is shaken and a large explosion is heard. They hurry to the window then turn on the television and discover from the news that the nearby Royal Hope Hospital has disappeared. Donna does not seemed so concerned by this; instead she begins looting the office for stationary to take when she leaves.
When she returns home the news reports about the hospital are still on the television – it has been returned. Wilf watches the screen avidly; convinced the disappearance is something to do with aliens. As the report continues it is announced that medical student Oliver Morgenstern was the only survivor. He claims that the hospital was invaded by creatures that looked like rhinos, and then explains that the building was slowly being devoid of air. Everyone suffocated apart from him because fellow student Martha Jones gave him the last remaining oxygen tank, she died as a result.
Whilst Donna and Wilf watch the television Sylvia examines the items Donna took from the office, including a raffle ticket. Donna confesses she thought her mother would be furious about her daughter being sacked but Sylvia confesses that following the recent turmoil concerning her husband, she is tired – and has given up on Donna.
The news reports continue – and Oliver Morgenstern reveals that when the hospital was abducted a woman named Sarah Jane Smith was present to look after everyone, apparently having been investigating the matter with her young son Luke and his friends Clive and Maria – all of whom were killed before the hospital returned.
That night Donna goes outside and walks along the street alone. Suddenly there is a flash of light coming from down a side alley and the woman from the scene of the accident at Christmas appears, claiming not to know what has happened. Again when the two speak the stranger appears more concerned by Donna’s back than the actual conversation, much to Donna’s annoyance. She claims that it is not the first time this has happened, several people claim they see something but when she looks she sees nothing.
The woman then cryptically asks Donna what she is doing next Christmas, and tells her to get away from London for a while. She tells Donna to use the raffle ticket she took from the office, which causes Donna to become very suspicious, having only taken the ticket that day. Again Donna asks the stranger her name but again gets no reply. She tells her to leave her alone and then walks away, unaware that she disappears in a flash of light once she is gone.
That Christmas, Donna wins first prize on the raffle – a luxury holiday over the festive period. Staying in a country hotel with Sylvia and Wilf the trio enjoy the break. On Christmas morning, however, they are shocked to discover more harrowing news reports – a giant ship modelled like the Titanic is plummeting from the sky towards London. As Sylvia calls for everyone to watch the report Donna is alarmed when a maid bringing in their breakfast points at her back, shocked by what she sees. She tries to see what might be there in the mirror, and almost catches a glimpse of some strange black creature, before hurrying to watch the television.
Seconds later there is a massive explosion in London, the shockwave bursting out right across the country. The television goes dead and the family runs outside, only to see a giant mushroom cloud rising above them in the skyline miles away. Wilf ponders that had Donna not won the raffle they would have been in London when the ship hit, and would have been killed along with everyone else.
In the aftermath of the explosion, the entire of Southern England is swamped with radiation and France has closed its borders. Donna and her family find themselves shipped to Leeds, where they are placed in an emergency housing scheme. Finding themselves sharing a tiny house with several other families; including an Italian clan headed by the cheerful Mr Colasanto. Whilst living in the cramped conditions they hear news of trouble in America, where sixty million people have been killed – all dissolving into tiny creatures made out of fat, which are then collected by a series of giant space ships.
Time passes and Sylvia grows more and more depressed, despite Donna’s optimism that she can find a job and get the family a new house. One night, when the entire household are bonding over a singsong, gunfire is heard outside. Donna, Mr Colasanto, Sylvia and Wilf hurry onto the street where every vehicle is spouting clouds of gas from its exhaust pipe. The soldiers patrolling the area open fire on the vehicles but to no avail. Suddenly one of the soldiers sees Donna and aims a gun at her, terrified that there is something on her back. When she turns around to reveal there is nothing there she is allowed to go.
However, instead of going inside Donna hurries to the bottom of the street – where she has seen a large flash of light. She does not seem surprised when she turns the corner and finds the blonde woman standing alone. They walk together and arrive on a park bench, where the stranger explains that all over the world people are being chocked by the poisonous gas, which is emitted by ATMOS devices fitted to vehicles all over the world. However, she claims a band of fighters are working to save everyone, and no sooner has she spoken a large blanket of flame rips across the sky, burning away the noxious fumes. She explains that Gwen Cooper and Ianto Jones of Torchwood died to save the world, and their comrade Captain Jack will soon be taken away to the Sontaran Homeworld – there is nobody left.
She then claims that none of the recent catastrophic events were meant to occur – the man who died underneath the Thames was meant to prevent them. She tells Donna that she was meant to be with him on Christmas Eve to help him to safety so that he would live to save the world again, she was meant to travel with him to distant worlds, just like she herself used to do…
Donna tells her she has no idea what she is talking about but the woman insists that she was meant to be there, claiming that now a greater threat is coming. She tells Donna that the universe needs the Doctor because now everything is in danger – hence her arrival from a different dimension. She claims that something is coming across the stars and it cannot be stopped. When Donna asks what “it” is the woman replies simply: “the darkness”.
Frustrated by the stranger’s need to involve her in this, Donna asks why she is so special, claiming she has done nothing of worth that would mark her out. The stranger claims that Donna is the most important woman in the whole of creation but she does not believe her. Tired and upset she returns home, but her would-be companion is not finished yet. She claims that soon, in three weeks time, Donna will choose to go with her and help save the universe, and on that day, she will die…
As time passes Donna finds herself saying goodbye to Mr Colasanto and his family – the emergency government has decreed that England is for the English – all foreigners must be rounded up. However, with the oceans closed they cannot be deported, instead they will be sent to special labour camps. Donna claims they have nothing to work for as there are no jobs, but Mr Colasanto cheerfully tells her they will complete such work as sawing and digging – it will good. However, both he and Wilf realise that the reality will be very much different – history is repeating itself in the most terrible ways.
During all of this Sylvia is slipping further into depression – sat alone inside the house. Donna tells her about her failed attempts to get work, having found nowhere that thinks she is qualified to work. She recalls how her mother told her to work harder at school and how she failed to do so, and claims that she must have always been a disappointment. All Sylvia can do is agree, the bravado and comfort she might have once held is gone.
That night Donna and Wilf sit in the open air glancing up at the stars. Again Donna recalls her failings – she had hoped to provide for her grandfather in his old age, but never found the money to do so. Again she seems to find no comfort, left to assume she really is useless. Wilf, however, is not distracted by depression; he is concerned that his telescope might not be working – all he can see is black.
As Donna looks on both she and Wilf realise that the stars are going out – eternal darkness is spreading across the sky. Recalling what the blonde woman told her three weeks ago Donna realises it is time for her to act. She turns around to find the stranger waiting for her.
Travelling in a UNIT jeep the two women arrive at a secret base where soldiers are hurriedly working on some sort of experiment. Captain Magambo, who appears to be working with the woman Donna has been stalked by, greets them. She reveals that even UNIT do not know the woman’s name, she guards it closely so as not to upset the balance of the universe.
The blonde stranger takes Donna to a tall blue police box standing nearby, wired up to various pieces of machinery. They step inside to a space much bigger than the exterior shell. The stranger explains that it is a ship, called the TARDIS, which once belonged to the Doctor. Once alive with light and energy the ship is dying, the central console now dull and the once-golden walls now blackened. However, some energy remains and it is being used by the UNIT soldiers for their experiments. Donna asks why the Doctor, a brilliant man, would travel with her, and her companion claims that really she is a brilliant person, it wasn’t until she was with the Doctor that she realised that. She, herself was exactly the same…
Looking once more at Donna’s back she asks if she would like to see whatever it is that is stuck there. Initially Donna refuses but on second thoughts, agrees to it. She is taken to a circle of mirrors placed nearby, which has been linked up to the TARDIS. Upon activation a series of lights illuminate the circle and the creature is exposed in the mirrors – it is a large black beetle.
Initially Donna is terrified by the creature but calms down. Her aide explains that the beetle feeds off of time, specifically changes in time. It takes hold of someone’s life and changes certain parts of it to create an alternate reality. In Donna’s case it made her take a path in life that caused her never to meet the Doctor and as such the whole universe has changed.
Suddenly Donna descends into tearful ferocity – claiming that when the stranger called her special it was a lie – only the beetle is special because it is responsible for what has happened. However, the blonde woman claims that after measuring certain readings concerning the beetle it was found that all of reality was bending and changing around Donna; they need her just as much as they need the Doctor – together the two can fight the approaching darkness.
At Donna’s request the circle is turned off so the creature is no longer visible, but Donna knows that the beetle is still there. She asks that it be removed and immediately the soldiers leap into action. Wiring up Donna’s jacket the stranger explains that they are going to send her back to the day where her life was changed – the day she turned right in her car instead of left. Her mission is to make sure her past self turns left instead of right so that history will not be changed.
Stepping inside the circle Donna appears to take solace in the fact that she will have to die, along with the rest of this reality, in order to restore the one in which the Doctor lives, one in which she is still alive. However, the stranger does not reply to this, and Donna begins to panic, fearing that even if she changes things she may still die. Before she can do anything else the circle activates and she disappears, sparks flying everywhere as the power of the TARDIS is tapped into.
Donna arrives on a street in London, but realises it is the wrong place – the junction where her car is about to turn is half a mile away. She runs as fast as she can, weary that she only has a few minutes in which to make the change.
As the past versions of Donna and her mother get into their car and begin their journey, present day Donna continues to run, but begins to realise that she will not make it in time. However, she can still stop herself turning right. Remembering that she is supposed to die she solemnly waits for her moment then strikes. Jumping out into the road she is hit by a lorry, causing a traffic jam that tails back to the junction where Donna and Sylvia are about to emerge, blocking the turning right.
As present day Donna lies dying in the middle of the road, the blonde woman she has encountered so many times before appears once again. She kneels beside her and asks her to pass a message on to the Doctor when the timelines are restored. She whispers the message in her ear and then Donna dies, just as her past self turns left, and reality is restored…
Back in the fortune-teller’s lair on Shan Shen, Donna awakens from her ordeal. The beetle that has attached itself to her back drops to the floor dead, and the fortune teller retreats, terrified by Donna’s strength. She questions what kind of person Donna must be to repel the creature, and fears for what she may become in the future…
Soon the Doctor arrives. Reunited at last Donna explains what has happened to her – relating the entire story of her altered existence, which is now slipping away from her. The Doctor inspects the beetle and explains that it is one of the Trickster’s Brigade, capable of changing a life. Usually the universe alters around the change but in Donna’s case an entire parallel world was created. He notes that this is not the first time – something similar happened in the Library.
Thinking further into the matter the Doctor considers the astonishing coincidences that have led to them being together – he met Donna once, then her grandfather, and then he managed to bump into Donna once more – as if something were binding them together. Donna retorts, claiming there is nothing special about her, but the Doctor claims that she is brilliant.
Suddenly Donna remembers the blonde stranger from her alternate reality, how she said something similar and how she told her to pass on a message to the Doctor. As he listens to what Donna has to say, hearing her talk of the approaching darkness, the Time Lord suddenly realises who the stranger may have been. He asks Donna what the message was and she replies:
It is Rose.
Panic-stricken, the Doctor hurries outside, where those two words are now spread across everything – every banner, ever poster, even the writing on the TARDIS is now replaced with the words “Bad Wolf” – bleeding across from Rose’s dimension into his.
He and Donna hurry inside the TARDIS, only to find it bathed in a blood red warning light. The Cloister Bell sounds and Donna asks what is going on. Realising that the walls between dimensions are starting to shatter, the Doctor tells her:
“It’s the end of the universe” .