Arriving In Norway

The TARDIS lands in a forest. The Doctor, Graham O'Brien, Ryan Sinclair and Yasmin Khan have arrived in present day Norway. While The Doctor attempts to ascertain where they have arrived, by tasting the grass, Graham spots a cabin in the distance, which The Doctor becomes suspicious of as it is the middle of winter but the cabin's chimney is not giving off any smoke. Despite Graham suggesting that it could just be used as a holiday home, and that currently no-one is there, The Doctor decides it needs to be investigated.

When they arrive at the cabin they discover that it has been boarded up as if it’s owner was expecting to ride out a storm. Taking a closer look Ryan catches movement in the bit of a window that is still available. The Doctor users her sonic screwdriver to scan the door, finding it locked by three locks, and unlocks them.

As the group enter the cabin, which appears to be deserted, they discover signs that someone has just had a meal recently. As they search Ryan and Graham investigate the upstairs where Graham finds sweet wrappers near a wardrobe which, when Ryan opens it, they discover a scared girl sitting in the wardrobe. The Doctor kindly asks her to exit, but the girl refuses to move. Graham asks if the girl is hungry, offering a sandwich he keeps on him. This does the trick and back in the kitchen, the girl eats Graham’s sandwich. When she finishes eating she asks who they are. The Doctor introduces herself and her travelling companions, explaining they were walking nearby and noticed something was strange about the cabin. The girl reveals her name to be Hanne. When she gets up, to put her plate away, The Doctor observes her feeling around for the sink. The Doctor asks if she is blind. In response Hanne removes her sunglasses, revealing that she is blind. Yasmin questions Hanne about who else lives there, prompting Hanne to explain that she lived in the cabin with her father, Erik, both of them having moved there following the death of her mother. But she now lives alone when her father was taken by a monster four days ago...

The Doctor Checks Where They Are

Curious about this The Doctor leads them all outside as Hanne explains that she checked for their boat which is still there, meaning that her father did not leave her by choice. Suddenly Hanne's watch starts to beep. She explains that it is set to warn her that the monster hunts at the same time every day. The Doctor sends Ryan and Yasmin to investigate a nearby shed, while she and Graham return to the cabin with Hanne. In the shed Ryan and Yasmin discover some dead birds and a work bench with partially constructed bear traps. When a roaring suddenly fills the air they run back to The Doctor with one of the traps, which indicates that Erik was aware that something was very wrong in the area. While Ryan and Yasmin block the back door, Graham goes upstairs so as to watch out of one of the windows. When the roaring stops, Graham turns and spots a mirror on the wall. Graham is curious about the mirror as he realises that it is not showing his refection. So absorbed by this mystery he is unaware when suddenly Ryan joins him. Ryan is equally confused by their lack of reflections. As Ryan reaches towards the mirror he causes some kind of energy to appear on the surface and his hand to distort into another space beyond it.

The Doctor then arrives and uses her sonic screwdriver on the mirror, pausing it in the middle of what it was doing. She sticks her head through the mirror, experiencing major perception distortion. She pulls back, noting that aside from the slight disorientation, she is perfectly fine. Yasmine and Hanne then arrive, wondering what was shaking the house. The Doctor explains that there is a portal in the mirror and that it is probably where Erik ended up. She instructs Ryan to look after Hanne, while she, Graham and Yasmin enter the mirror.

Hanne

They find themselves in a maze of rocky tunnels and caves. Drawn to a light in a cavern they come across a strange being named Ribbons, who lives in the bizarre world. The Doctor asks for his lantern, but Ribbons offers it in exchange for The Doctor’s sonic screwdriver. The Doctor reluctantly agrees but only promises to hand it over if he shows them the way to Erik. So that they can find their way back The Doctor uses string to leave a path. They have not travelled far before they discover a dead body while a moth lands on the lantern. Ribbons explains that it is a flesh moth, tossing a dead rat to lure it away. He lingers under a false pretence in order to cut the string. When they arrive in a new cavern Ribbons suddenly takes Graham hostage to renegotiate the agreement he made with The Doctor. When a new moth arrives The Doctor, at her wit's end, asks where they are to which Ribbons reveals that they are in an Anti-zone. The Doctor explains to a confused Graham and Yasmin that this is a buffer between realities. When more moths arrive Ribbons attempts to run off, with The Doctor’s sonic screwdriver, but is tripped up by Graham. The moths descend on Ribbons and before anyone can come to his aid he is eaten by the moths. Having finished with Ribbons the moths start to chase The Doctor, Graham and Yasmin as they desperately try to find their way back to the portal and so to safety. They manage to reach the portal and when they pass through they find themselves back in the cabin. However, The Doctor soon realises that something is not quite right. Everything is the mirror image of what it is supposed to be. The Doctor deduces correctly that they have reached the other side of the portal and are now in a reflected parallel universe.

As they go downstairs The Doctor, Graham and Yasmin hear someone in the kitchen. There they encounter Erik. When they explain to him that Hanne is being menaced by a monster, Erik explains that there isn't one. It is just something that he invented to keep her inside the cabin, with a fully stocked fridge, while he is away. The Doctor notices that Erik is trying to hide the fact that there is someone else in the cabin. A woman named Trine enters the kitchen and The Doctor automatically assumes that Erik has married someone he has met in this world. However, Erik explains that Trina, despite her being dead, is Hanne's mother.

Back in the real universe Ryan also discovers that the monster is not real when he finds some speakers around the house and realises that they are being used to keep Hanne inside. Before Ryan can tell Hanne about his discovery she knocks him out before entering the portal herself. On the other side of the mirror she finds The Doctor's string and begins following it. Shortly afterwards Ryan comes to and realising that Hanne has gone through the mirror he passes through the portal himself. He soon catches up with Hanne just before they arrive near Ribbons' corpse as the flesh eating moths arrive. Ryan sends Hanne away as he hides from the flesh moths.

Graham Discovers the Portal

In the reflected parallel universe Graham hears a humming coming from outside. In amongst some laundry drying on the line he discovers Grace. Despite knowing that this can’t be the real Grace, as she died (see "The Woman Who Fell to Earth"), Graham tells her about his travels with The Doctor and even meeting Rosa Parks. The Doctor joins Graham and quickly deduces that they have encountered the Solitract, a sentient universe incompatible and exiled from the real one, which seeks companionship and has now cut them off from their universe. Hanne then arrives and immediately identifies that the version of Trine within the Solitract is not her mother. Hanne is ejected back to the anti-zone when The Doctor convinces the Solitract to let them all go, knowing their presence threatens to collapse it. However, when Erik refuses to leave, The Doctor offers to take his place and give the Solitract her broad experience from travelling the universe. When Erik is ejected The Doctor finds herself in a white space. She sees archways leading up to a chair with a frog on it. The frog speaks to her in Grace's voice, explaining that a frog is its most favourite form, so this is its true shape. Despite being fascinated with interacting with the Solitract, The Doctor explains that she can not stay for long and urges the Solitract to let her go. When the Solitract agrees The Doctor promises to be best friends forever with the Solitract and the Solitract promises to dream of its new friend.

As the anti-zone collapses, everyone runs back to the portal to the normal universe. As they reach the portal Ryan wonders where The Doctor is and immediately hears a yell from her to run. She rushes towards them as they all head back through the mirror. Once they are all through, The Doctor uses her sonic screwdriver to sever their world's connection with the anti-zone and explains that the Solitract can not come back to their universe.

Having received closure from the Solitract, over losing his wife, Erik decides to move with Hanne back to Oslo. Back on the hill, as they approach the TARDIS, Ryan and Graham talk about how Grace would have reacted to this whole adventure. Laughing, Ryan finally calls Graham ‘granddad’, pleasantly surprising him. Shortly after they enter the TARDIS it dematerialises.