This time the journey was like the Professor had described, falling through indistinct darkness. Forms whirled around them, like grey flowers budding and unfurling, all a blur of creation and growth and death, the endless cycle of everything. Then, with nothing more than a gentle thud, they landed on snow.

And she was back in Narnia.

It was dark, pitch dark; and cold, so much colder even than that first time through the wardrobe. Susan could see nothing at all, not even Brian who was still on her shoulder, and had woken up with a shiver. She could feel the frost crystals forming on her, every water droplet on her hair, skin and eyes, freezing, the dopiness of the intense cold taking her...

'This will kill us!', shouted Susan; but Lafey was already whispering a spell and suddenly there was warmth, a funny bubble of heat that enclosed Susan like a thick coat. It was still chilly, and she could feel the ice on her breath, but it was no longer dangerous. Then Lafey conjured a glowing sphere. She threw it up, and it brightened as it soared, and it lit the landscape around them, and they could see what had become of Narnia.

They were standing on a featureless tundra, a flat plain of snow that stretched as far as their little light could show them. There was no wind, no stars. It was just grey ground under a black sky, as silent as a grave, as cold as despair.

Lafey flew up to see further.

'I can see the door,' she called.

They set off as quickly as they could, trudging over the snow. Only Brian was happy; now he was warm, he leapt over the ground, making little squirrel burrows, darting here and there, shaking his fur and laughing. The others, though, felt the weight of the absence of life, in terrible contrast to the living wood they had come from. They didn't speak until they reached the door, although Susan smiled at Brian when he threw snowballs at her.

It was nothing much: made of unsanded wood, unpainted, held together with iron nails. Identical on both sides. Golden light seeped through the cracks. It was untouched by the frost, and sitting above the snow as if it was part of another world. Which, thought Susan, it actually was.

Skittlestone shivered from a memory that had nothing to do with the cold.

'There it is again. That's where the missus went, and the kids too. I hope. Don't bother trying to open it; it's held closed with more than a latch.'

He tried to stare through; but there was nothing to see. He turned away, his voice brittle with disappointment.

'They really are gone.'

It was the quietest Susan had ever seen him. She crouched down, and put her hand over his shoulders.

'Are you OK, Skittlestone?'

He shook his head, blinked his tears away.

'I think I'd like a moment, thank you,' he said. She nodded and stood up.

'Look at this,' said Lafey.

Lafey was hovering above a lump in the snow, the thrum of her wings sharp in the silence. Susan joined her, and then crouched down, and started clearing away the snow with her hands. Brian thought that this looked fun, and joined in. It didn't take long for the two of them to uncover it: a metal bar, ripped from an old-fashioned gas street lamp.

'This is from Earth,' said Susan. 'The Witch brought it here when Narnia was created. It sprouted into the lantern. It's a bit of a surprise to find it here, though: I didn't think the stable door was close to that place.'

Lafey shrugged. 'This is all there is of this realm now,' she said. 'There is nothing but ice and bones and the door and the bar; things that mark the beginning and the end of Narnia. So it's shrunk. It must be why there is still water in the pool. This last little thing wasn't part of the world, so it didn't end when everything else went. It's keeping the whole thing open. If we take it, Narnia will snap shut. I think we should.'

Susan was about to agree with her, when she heard something, a whisper at the edge of her hearing.

'Susan...'

'We are lost...'

She looked around, trying to find the source.

'What's the matter?', asked Lafey.

'Can't you hear that?'

'No. What are you talking about?'

She looked around at the others. Skittlestone was staring at the door, grieving; Brian was making a snow squirrel; Lafey was hovering just in front of her. The donkey was staring into the distance, not doing anything much. None of them could hear what she could hear.

She could see things now: wisps in the darkness, pale shapes that flitted above her and around her. They were whispering, begging; so sad and so, so alone.

She glimpsed a giant's hand, a rabbit's tail, a human foot, insubstantial, phantoms that were as solid as mist. They knew of themselves, but not of each other; yet they could see her and she was the first living thing they had seen for so long... And she somehow knew that all they could feel was regret and remorse and a weight of emptiness that sat on them like stones.

When she had met the dryads on the Heath, she had been afraid; but now all she could feel was pity. These were souls like her, excluded from their paradise. The lion had locked the door and they were all on the wrong side.

They were swirling round her, the whispering becoming louder, sadder, more urgent. She looked up, saw the faint ball of light that Lafey had thrown in the sky; but beyond that, far into the Narnian space she saw a single star. It hadn't been there before, she was sure of it. It brightened, briefly. And then it disappeared.

And when she saw the star, she knew what to do. Something filled her, an urgency that she had not had before.

Now the others could hear the spirits, too, and they were looking frightened. Brian was hiding behind Skittlestone, who in turn was looking grim, ready to defend his son at all costs. Lafey was preparing some magic, preparing to fight. The donkey stared at Susan, its face unreadable.

'Iris,' said Susan. 'these spirits are not dangerous; but we need to go back to the wood.'

Lafey nodded, and made a gesture; and they were travelling again.

This time it was different again. She was carried by the cloud of souls, eager to see sun and warmth again; they swam around her, whispering and laughing and begging and sobbing. She could feel their despair turn to hope; and yet the loneliness and the death hung around her like acrid smoke.

She could also feel the tension and the magic of the star. It crackled in her, electricity desperate to earth.

When they arrived in the wood, she started walking to the Earth pool, and the power of the star thrummed through her. She knew without looking that as she drifted her hand through the air, sparks fell, and that her hair was floating around her head like a great black halo. She was young again: not the child that walked in Narnia, but the woman who chose to stay at home, who saw the wreckage of the crash, who went to a quintuple funeral.

The trees held up their branches, and flowers appeared; petals fell around her. The grass grew and waved. When she breathed, a terrible gale caused all the leaves to shake.

Her companions were terrified, didn't understand. Even the wood's calm could not still their fright. Their mortal fear echoed around her, and she was sad at that, but she could not afford to stop. She held out her arms and dropped into the pool as if she was falling onto a vast bed, and pale flames shivered from her.

She didn't need Lafey's magic any more. She carried them, all of them, the living and the damned, all of the lost and the forgotten of Narnia with her, all the ones scattered across Earth, as she tumbled through the void. Instead of ending back in London, though, she kept going to somewhere else, another place that she had never been to before, the furthest she had ever travelled.

It was a single planet, orbiting a sun-like star. It wasn't quite big enough, so she smashed a moon into it, changing its orbit and its rotation; then she cooled it, and pulled icy comets from the edge of its little solar system to rain down water on its molten surface. As she did this, she sang; a song from the deep magic, one that she had never heard before, but knew the same way she knew sorrow. It was not the mighty song that Aslan had sung when he had created Narnia; it was a slower song, a song of regret and death, but it was beautiful nonetheless.

When the planet had oceans, her song became louder, and those oceans blossomed with algae, and oxygen flooded the atmosphere. She made single celled creatures, simple animals that ate and inhaled; then she pushed life out of the seas and onto the shores, and it exploded into grasses and bushes and trees.

She felt a hand slip into hers. Somehow she knew that it was a shadow of George, a last splinter of his existence, come to be proud of her once more. She started weeping, but the song came from her anyway.

She filled the skies with insects; they buzzed from flower to flower, pollinating and courting and dying. She filled the seas with little fish, sea stars, and jellies, but stopped there. She wanted no higher life on her world, no more souls to weep for.

A hand landed on her shoulder, lighter than a kiss. Her brothers and Lucy were watching, and they were smiling. Her tears were pouring now, great rivers of regret that salinated the seas, and she coughed with the sorrow as she sang, but the song kept coming.

She built homes, snug and warm, a string of towns on islands in an archipelago ringed with limpid green waters. On the central island she sang a library, huge and graceful, full of every book that had been written and many more that had not. She sang other wonders, none of them magical themselves, but all filled with the magic that is the love of a creator for its creations.

Finally, she sang bodies for the spirits, made them as they remembered themselves, blood and bone and sinew. Because she wasn't in Narnia, she was bound by the rules of this universe, and now she needed to use magic for the magical creatures; but the magic she used was the shallow magic, the sort that would gently dissipate after their deaths, and didn't need the universe to be changed.

And lastly, when she saw her parents looking down at her, she finished the song on a note that meant the occupants of this world were all barren and would have no children, because this was truly the end, and the sins of the parents would not be visited on the children. And the lost of Narnia woke on the grass of this young place and stared into the sky in wonder as the ghosts of Susan's past faded like old memories.