Although her eyes were closed, Bianca could see she was surrounded by a blazing bright light. Am I dead? she wondered, blinking her eyes open.

When she moved her arms, she found she was lying on her back in a soft eiderdown of powdered snow. The vast blue sky above her appeared to be held up by tall trees dressed in snowflake coats. Sunbeams bounced about like ping-pong balls. Bianca laughed with delight, swinging her arms and legs out in great arcs to make an angel.

Curiously, she found her right hand wouldn’t swing as freely as her left. She lifted it, checking and turning it. It looked normal. Then she heard a man’s voice, like a distant echo.

‘I’ve got your hand Bianca. I won’t let go.’

‘Who’s there?’ she said, sitting up.

Bianca saw she was alone in a snowy clearing encircled by fir trees. She twisted onto all fours, letting out a startled yelp as she found herself nose to nose with a brown-eyed reindeer.

She crawled backwards, blinking. The reindeer drew back and blinked as well. Bianca tilted her head to the right, and so did the reindeer. She tilted it to the left and let out a laugh of surprise as the reindeer mirrored her once more.

‘Well, who are you?’ Bianca asked.

‘Pordis,’ said a girlish voice inside her head.

‘Who said that?’ Bianca looked around, alarmed.

‘Pordis.’

Bianca leaped to her feet and the reindeer jumped backwards.

‘Who’s there?’ Bianca stared into the shadows between the tree trunks.

‘Pordis,’ came the voice again.

‘Show yourself, Pordis,’ Bianca called out bravely, hoping she looked less scared than she felt.

The reindeer trotted around Bianca and stopped right in front of her.

Bianca looked questioningly at the reindeer. ‘You are Pordis?’

The reindeer bowed its head.

‘I am Bianca.’

‘Yes.’

‘And you are Pordis?’

‘Yes.’

Bianca looked around to reassure herself that she was indeed having a private conversation with a reindeer.

‘Where are we?’

‘Together,’ Pordis’s soft voice said inside her head.

Bianca laughed, reaching out her hand and

tentatively giving Pordis’s coarse caramel coat a stroke. She sensed a bond with this creature. She knew it somehow. They were friends, companions. ‘Yes, Pordis, but where are we together?’

‘Firfrost Forest.’

‘Firfrost Forest,’ Bianca echoed, searching her mind for the story of how she came to be here, but she drew a blank. She looked down at her clothes. She was wearing a coat and underneath it a purple knitted jumper that was far too big for her, with a white B on the front. A red ribbon of knitted wool was tied round her left wrist. When had she put these clothes on? Her brain gave her no answers.

‘I was doing something,’ she muttered. ‘I’m sure I was. Something important.’

But, try as she might, Bianca couldn’t remember anything about what had gone before this very moment. To her surprise, she didn’t seem to mind.

Slipping her hands into her coat pockets, she found an orange diary and a pen.

‘Are these mine?’

‘Are they your pockets?’ Pordis replied innocently.

Bianca laughed. ‘Yes, they are!’

The orange diary was held shut with a piece of black elastic. Sitting down in the snow, Bianca opened it. She flicked through the early months of the year: January, February, March. They had dull and routine entries, things like ‘Went to Casper’s house’ or ‘Flute lesson’. Her brain seemed to know who Casper was and that she played the flute, but no further details. She was about to give up on the diary when a piece of paper fell out of the back. The page it fell from had drawings of four children on it: below the picture of a boy in a bearskin she had written QUILO, beneath a picture of a boy and girl holding hands she’d written PITTER and PATTER and the last figure wore a suit, and a top hat, and was called JACK. She unfolded the paper that had fallen from the diary and found she was looking at a crude map of a city. Had she drawn it? Was it something to do with how she’d got to Firfrost Forest? Suddenly she saw a name that made her heart vibrate like a plucked harp string: FINN.

‘Finn,’ she whispered. A vision bloomed in her head of a five-year-old boy with ash-blond hair, wide blue eyes, a snub nose and a toothless grin. He’d lost all four of his front teeth in the same week and had been so excited about the tooth fairy’s visit. She remembered!

‘Finn?’

‘Oh, Pordis, Finn is my little brother. Something has happened to him.’ She frowned. ‘I don’t remember what, but I think it’s bad.’ Why couldn’t she remember? ‘I think I’m looking for him.’

‘We are looking for him,’ Pordis corrected her.

‘Yes.’ Bianca got to her feet, stuffing the map back into the diary. Glimpsing the red scarf tied round her wrist again, she grasped at a hint of a memory teasing the edges of her mind. ‘This is his.’ She held up her hand, showing the reindeer the makeshift bracelet. ‘We are looking for him. That’s why we’re here. I don’t know how we arrived in this place, but we’re searching for my little brother.’

‘Finn?’

‘Yes, my little brother, Finn.’ Bianca put the diary back in her pocket and looked around the clearing. There appeared to be only one way out, so surely that must be the way they'd come in? But there were no footprints to suggest which direction she and Pordis had come from. Had she slept here while the snow fell? How long had they been here, in this grove?

Pordis nuzzled her nose into Bianca’s side.

‘What is it, Pordis?’

The reindeer shook her antlers.

‘Climb onto my back.’

‘Really?’ Bianca’s eyes opened wide with surprise. Did she know how to ride a reindeer? There was only one way to find out.

Pordis’s toffee-coloured back was bony and about as high as a donkey’s. Bianca found it easy to lift her leg over and climb on, but the reindeer’s broad white neck didn’t have a mane for her to cling to. Bianca lay forward, gripping the reindeer’s haunches with her thighs and reached up to hold on to the antlers. ‘Like this?’

‘Yes. Are you ready, my Bianca?’

‘Ready as I’ll ever be,’ Bianca replied, hoping she wouldn’t fall off. ‘Let’s go find Finn.’