Maria assumes that the girl standing next to Sarah is Andrea, and when she grabs a nearby newspaper she discovers it is 13th July 1964, the day of the accident. She tries to warn the to girls not to venture onto the closed pier, knowing that the blank-faced creature must be about to arrive (recognising the reason she appeared in 1964 is because the creature must have visit there as well to switch the two girls at the moment of the accident).
Andrea, assuming Maria to be mad, drags Sarah away and when their backs are turned the small creature that captured Maria arrives. It shoots the two metallic electrodes from its gun at her and once again she is taken away. Meanwhile, Sarah and Andrea have been trying to get past the locked gates of the pier. Eventually they succeed but not before Sarah notices the sudden disappearance of their brief acquaintance.
Maria reappears in a white void. Her captor releases the two electrodes from her lapel and then leaves. Looking around anxiously, Maria is jubilant when she finds Sarah Jane, who has been deposited in the void as well. The two embrace and Sarah explains that they are in limbo, an empty space.
Back on Earth Alan and Chrissie continue to argue. Alan tries to convince his estranged wife that they once had a daughter but she denies it, claiming that if they had they might never have split up. Alan then realises that the metal box he found must have protected him, just as it had done for Maria. Now knowing that Maria was telling the truth and that Sarah Jane must indeed exist, he leaves the house, despite Chrissie showing him pictures of the day he moved home, depicting himself, Andrea, but no Maria.
In the void Sarah recalls the day Andrea died when she fell from the pier, revealing she had always pondered that it could have been her that fell, and now the timeline has changed her thoughts have become reality. Maria interjects and claims that if Sarah ceases to exist on Earth then the meteor must still be on the way, and no one can stop it but her.
Sarah asks how Maria still knew of Sarah when the rest of the world had forgotten. She explains about the box and Sarah realises the Soothsayer who gave it to her must have known what was due to happen, and thus gave it to her to give her some chance of being saved.
Maria confesses she dropped the device back on Earth then inquires about the creature that captured her. Sarah explains that it is a Graske but theorises that what has happened is too powerful for such a creature to manufacture, it must be a slave for something else. Suddenly a ghostly voice rings out, calling her name. She warns Maria to stay where she is, then walks off to find the source of her summons, disappearing into the fog.
In Bannerman road Andrea welcomes the guests at her birthday party, whilst in the void Sarah confronts the hooded creature that changed the timelines. It lifts its hood to reveal its blank face, punctuated only by a fanged mouth. She asks its name but it claims it has none, it is “nothing”. Explaining that it feeds off of chaos in order to survive, the creature tells Sarah that she is the key to the food it needs. Without her in existence the meteor will collide with Earth and then the creature can draw energy from the resulting disarray.
It waited for just the right moment to snuff out her life, and to ensure the course of history was not changed until it deemed fit to interfere, he turned away the creatures Sarah has fought on her own on Earth; the Slitheen, the Gorgons, even the Bane. It tells her that since the Bane never came to Earth her son Luke was never born and therefore he now exists in ‘The Forgotten Places’, even further out into the void than Sarah and Maria.
Sarah asks why the other creatures were expelled from Earth and it explains that the results of their plans do not result in chaos; they are the fruits of revenge or the lust for power. The meteor represents none of those things, it happens by chance, and thus brings true pandemonium. Sarah is hurt by the fact the creature doesn’t care about the billions of people and animals that walk the Earth, but it insists it cares about her, for her life was so important to its plans. It explains that on 13th July, the day of the accident, he saved Andrea’s life by switching her and Sarah so that it was her who fell from the pier. However he could only do so once Andrea had agreed to let Sarah Jane die in her place.
Sarah seems hurt and protests when the creature turns to leave. It plans to return when the Earth has been destroyed and claims that she will still be of use to him, with her memories he can locate the Doctor and delete him from history, the amount of chaos such a deed would bring would create massive supplies of energy for him. He fades away as Sarah screams out in protest against his plans concerning her old friend, but her cries are unheard.
At Andrea’s house Clyde arrives, shortly followed by Alan and Chrissie. Meanwhile, Sarah returns to Maria and comforts her, claiming there is nothing and no one who can help them, they’ve been forgotten. On Earth Clyde turns on Andrea’s television to view a news report, which claims a meteor is about to collide with Earth. Alan recalls what Maria said to him about such a happening and begins to worry, but Clyde claims the projectile will miss the Earth.
Andrea, calmed by Clyde’s declaration, goes to the kitchen to fetch more glasses. Alan follows her and confronts her about Maria and Sarah, but she claims not to know of them. She changes her tune when he shows her the metal box that protected him, and warns him that they cannot be saved. He demands to know hat has happened to them and she takes him up to the attic, where she explains what happened the day of the accident.
She and Sarah ran onto the pier, and when she leaned on the barrier to look out at the sea it gave way, causing her to fall. She grabbed onto a ledge hovering over the rough waters below, yet despite Sarah’s efforts to help her back onto the pier she couldn’t hold on any longer. It was then the hooded creature intervened, calling to her and telling her that it could save her life if she gave her permission for Sarah to die instead of her.
She agrees to the proposition and in a flash the scene had changed, now with Sarah dangling over the sea whilst she stood safely on the pier. She watched as her friend dropped from the ledge to her death, and was then confronted by the creature and its Graske slave. The creature presented her with a metal box identical to the one Alan now possesses, and told her that she would forget what had happened so that she could live a full life.
For over forty years she had forgotten about the transaction, but Maria’s visit made her remember again and for that she had to be sent away as well. Andrea begins to break down in tears and she confronts the mirror hanging on the attic wall. The hooded creature appears within it and tells her that with her agreement Alan can be removed as well. Distraught, she gives her permission and grabs the metal box from Alan’s hand. Suddenly the Graske arrives and chases Alan from the house.
In the living room Chrissie, Clyde and the other guests continue to watch the new report, which claims that the RAF will destroy the meteor before it reaches Earth. Chrissie turns to see he ex-husband being chased by the alien creature but assumes it is merely a man in a suit. She returns to the living room where the news reported explains that the missile strike intended to destroy the meteor has failed.
Alan manages to evade the Graske and capture it, tying it up in his own home with the curtain cord, demanding to know where his daughter has been taken. Meanwhile, the guests from the party rush outside to watch the meteor approach. Andrea realises what Maria said to her that morning, that Sarah Jane was the only one who could avert disaster.
The Graske shows Alan how to retrieve Maria using its gun, and sure enough seconds later his daughter is back beside him. Outside Chrissie suddenly remembers her daughter and runs off to find her. Inside the house Maria tells her father that they must save Sarah in order to save the Earth. He repeats the action with the gun that retrieved his daughter but Sarah doesn’t appear. Maria theorises that is she herself was returned to her home, where she belongs, Sarah will be returned to where she belongs; her attic.
They hurry outside unaware that the Graske has freed itself, teleporting away. Up in the attic Andrea tries to seek solace in her metal box but is distracted when another apparition appears in the mirror; Sarah Jane. They welcome each other before Maria and Alan arrive. Sarah explains she cannot return whilst Andrea lives, and explains that only her childhood friend can bring her back, by retracting her previous agreement and dying instead of Sarah back in 1964.
Andrea protests after Maria claims she was meant to die, claiming that she has lived her life to the full and made the most of existence. Sarah cuts in and claims she had done the same before she was betrayed, and tearfully begs Andrea to change the timelines back and save her son. However, her friend fears being wiped from existence only left forgotten and refuses. Sarah protests that Andrea was never forgotten, it as her accident that showed her how precious life was, and as a result she fought to defend it ever since.
Andrea’s eyes begin to fill with tears as the hooded creature arrives. She confronts it and orders it to retract their agreement. It tempts her, claiming she will die as a result but she retorts that she has been dead for forty years. She turns to Sarah Jane in the mirror and bid her farewell, before shattering the mirror with the metal box given to her by the creature.
Suddenly the timelines are restored. Back in 1964 Andrea resumes her position dangling from the end of the pier, saying goodbye to her friend once more with the words “Remember me”. She falls and in the present day Sarah and Luke are returned to Earth, finding themselves in the reformed attic with Sarah and Alan. Outside the meteor roars ever closer and Sarah calls upon Mr Smith to help. He activates the magnetic field and the meteor is deflected back into the skies, the Earth is saved.
Sarah celebrates the return of her son and promises he will never be taken from her again. Clyde arrives to join in the jubilations, which are somewhat stunted when the group realise Alan has witnessed the entire incident. He still remembers the aliens and monsters, and has now seen Mr Smith. He turns to Sarah, Maria, Luke and Clyde and demands some answers.