Once there was a girl who was in love with the night sky.

She had visited planetariums and read children's books on astronomy. She had learned to identify nineteen different constellations and would always look for them on dark, clear nights. She had gotten her father to stick glow-in-the-dark stars and planets to her bedroom ceiling. She had eaten freeze-dried astronaut ice cream and thought it tasted better than anything else in the world.

As time passed the girl began to learn about the universe, about things like asteroids and black holes. Little by little she came to know the invisible forces that governed outer space, and the night sky became more than just a sky to her. It was a giant treasure box, filled with the secrets of the places beyond earth.

The girl's love slowly turned to longing. She wanted to know the stars through more than just pictures and models, because deep down she believed that there was something in the universe she couldn't find on her own planet. The thought settled deep in her, and tugged at her until it ached.

One night she lay awake in the dark, looking straight up at the ceiling. She was thinking of the black sky blanketed with stars - so many distant suns. Closing her eyes, she held out an imaginary hand and reached up into the sky. Her bed fell away, the walls fell away, gently and silently, and then she was flying, past the solar system and out of the galaxy. On she flew, further and further into space. She was so focused on making the journey that it came as a great shock when something touched her imaginary fingers and suddenly spoke to her.

'Who are you?' it asked curiously. It was a strange and wonderful creature, hard to figure out by looking.

'You're an alien!' the girl cried. 'Where are you from? How did you find me?'

'I come from a distant dimension, a very wide and fluid space. It's quite nice there,' the alien said modestly. 'From my home, I can observe almost anything I wish. I could tell that you wanted to find me, or someone like me, and I wanted to learn more.'

The alien paused, and the girl knew that it was studying her. Finally it said, 'You are unique. I have never encountered anything quite like you before, and it is very rare for another being to come seek me out.'

The girl couldn't wait any longer to say the words. 'Take me with you.'

Now it was the alien's turn to be surprised. 'Where?'

'Anywhere. Take me to all the places you've been. Take me to meet other aliens. Anywhere, just so long as it's far away.'

'I can't do that.'

Tears of frustration and disappointment stung the girl's eyes. 'Why not?'

The alien sounded regretful. 'We are very different. This hasn't stopped us from communicating, but I do not know how you would survive the trip as you are now. To take you with me safely, I would need to alter you - to make you almost like a part of me.'

'It wouldn't hurt, would it?'

'Not at all. But it could change you in a way neither of us would like.'

The girl considered this. 'I still want to go.' She began to cry. 'I've been waiting forever to meet you. I never even knew if aliens existed, but I always wanted them to. And now I've met you, and you've traveled so far, and...' Her voice sounded tiny in the cold vacuum between the stars. 'I'd feel awful if you just left me.'

'Is it so terrible where you are?' the alien asked.

'If I could be with you, I would be happier.'

The alien glowed with interest. 'In that case, I think I can still do something for you. I'll send you back with a fragment of me instead.'

'Really?'

In response the girl felt something explode into her mind. It felt like a giant flower unfolding inside her, a flower made of millions of petals, and each petal was a new and unfamiliar thought. Suddenly she knew what it was like to be at the center of a supernova; to watch icy storms at sea on a strange planet; to move through a dimension where indistinct shapes twisted and coiled in the atmosphere like dragon snakes. She went through all of the experiences in a second, and she knew that all of them were the alien's.

In the middle of the stream of visions the girl saw herself, like looking in a mirror. It startled her, because she was seeing things she had never seen before - cells, atoms, memories, thoughts, wishes and dreams, all fitted together in a hypnotic pattern that seemed to flicker and burn - almost, she thought, like a star.

The visions faded away, leaving behind faint shadows and something else, something alive. It stayed with the girl as she began to fall back through space in the direction of home, and the weird and wonderful being she had wanted to meet for so long dissolved into the darkness.

'Goodbye,' the alien said. 'I wish you both well.'

The girl was jolted awake, lying in her own bed again. It was still the middle of the night.

Was the alien just a dream?

No, it wasn't. The girl felt strange, as if there was a second heart beating inside of her own. And a will that wasn't quite hers was making her slip out from under the covers, walk across the carpet and stand in front of her closet mirror. It lifted her hand to her face and touched her cheek, smiling at her reflection in wonder.

'This is... our skin. Our body,' said the new presence in the girl's voice.

'Yes. Yes, it is.' The girl was shaking a little.

'Please don't be scared.' This time the presence spoke through the girl's mind. 'I like being with you, and everything is so new here. You can show me the rest, can't you?'

This time, the girl smiled. 'Yes. I'd love that.'

And so the girl and her new companion remained side-by-side in the same body, sharing each other's company and sometimes their thoughts. The little alien was thrilled by the smallest things in their daily life - telephone poles, for instance, and twigs at the bottom of a stream. Everything seemed fresh and exciting the way the alien saw it, and its enthusiasm was infectious.

One night the little alien led the girl up a grassy hill with a telescope. Together they peered through it, and instead of the sky the girl found that they were looking at city lights twinkling in the distance. 'They're beautiful, aren't they?' asked the alien. 'Like the sky fell to the ground.'

'I never really looked at them before,' the girl said, 'but you're right.'

When they folded the telescope and walked down the hill, the girl looked up at the stars. Even though she still loved them, she didn't feel that desperate pull anymore; for the first time, she was fine being where she was. She had a friend - and together they had fallen in love with the world.