‘Pordis,’ Bianca gasped. ‘They’re going to find us!’

‘What shall we do?’

‘I don’t know!’ Bianca looked about in alarm. ‘We’re going to have to split up. You creep to the back of the tent. I’ll edge towards the side. Stay low. Try and find a moment when you can dodge out of the door without being seen, then run as fast as you can. I’ll do the same, but I’ll slip out the side, under the tent flaps.’

‘I won’t leave you,’ Pordis said. ‘You’re my herd.’

Bianca leaned her forehead against Pordis’s long snout. ‘You’re my herd too,’ she whispered. ‘But you must do as I say. When the coast is clear, we’ll meet down in the cove, where we saw Casper. OK?’

‘Yes, my Bianca,’ Pordis replied, as Bianca hurriedly untied the branches she’d strapped to the reindeer’s antlers.

The penguins cleared the stage, getting ready for the next act, and the audience grew impatient, wriggling and chattering.

‘Go, go, go!’ Bianca hissed, removing the blanket and fake tail.

As Pordis retreated, Bianca sneaked forward.

The audience fell silent as a small grizzly bear lumbered onto the stage on all fours. From the opposite wings, a pale willow-thin figure in a white suit and black top hat strode forward.

Bianca’s whole body stiffened in shock. It was Jack!

The pale figure bowed, removing the top hat. Reaching into it with a gloved hand, the white-eyed magician pulled out a long ivory silk scarf, tossing it high into the air. As it reached the apex of its flight, the scarf divided into a hundred tiny fluttering butterflies.

The grizzly bear sat back on its haunches, puffing little eddying breaths at the silk butterflies, sending them whirling upwards, as the Arctic orchestra played a puckish tune.

The audience cooed, but Bianca was transfixed with fear.

Jack’s eyes glittered, looking everywhere and nowhere at once.

Bianca didn’t dare move. She couldn’t tell if she’d been seen or not.

Jack took off the white gloves, revealing giant snowflake hands, and an image flashed into Bianca’s mind of Jack standing by a big machine, ice spooling from those unnatural fingers, making silver books.

I remember! Bianca thought, fixing the image in her mind. I remember the books!

The grizzly bear threw back its head, revealing the rosy-cheeked face of Quilo.

The audience clapped and cheered.

Bianca screwed her eyes tightly shut, and focused her entire mind into two words. ‘RUN, PORDIS!’ she shouted, silently, inside her own head.

Hearing Pordis grunt, Bianca looked over her shoulder and saw the reindeer cantering away from the tent.

Quick as a flash, Pitter and Patter were sprinting after her. Bianca shuffled sideways, trapped between children, unable to run.

One of Jack’s strange hands waved in a graceful arc, making a frost fern grow in the air before them. The tune from the orchestra sank into a minor key as Quilo took a deep breath and puffed a ball of wind at the glistening plant, shattering it into shards. The wind created a vortex in which the crystals spun, and the music built, as if this had all been rehearsed.

Jack slowly turned, smiling right at Bianca, breaking her free of the trance created by his ice-conjuring.

Fear flared inside her chest, and Bianca bolted for the nearest side of the tent. Hearing Quilo’s roar, she glanced back and saw the ice shards, like stiletto knives, flying towards her back.

Throwing herself to the ground, Bianca rolled out of the tent, wrenching out pegs.

Stumbling to her feet, she ran blindly away from the marquee, certain that Jack and Quilo were right behind her.

She was shocked to find that Winterton was empty. All the children and animals were inside the theatre tent.

They lured us in with the music, Bianca realized as she ran. Was the show just a trap for me?

If all the children in Winterton were inside the marquee, and she hadn’t seen Finn, then Bianca knew, with a soul-darkening dread, that there was only one place left that her brother could be: inside the ice fortress.

She ducked down behind a coconut shy with sculpted ice targets and snowball ammunition. Running bent double, she made it to the helter-skelter, risking a glance over her shoulder as she rounded the cylindrical slide. She didn’t see anyone following her, but she knew they couldn’t be far away. Her breath was coming in short gasps and her throat burned.

Darting away from the slide, she made it to the base of the Flurry Flake, pausing for breath as she hid behind the wheel’s drive mechanism. Then Bianca put on a burst of speed, sprinting under the WINTERTON sign and down the rocky path back to the sea.

Hurtling down the track at a breakneck pace, Bianca burst out onto the beach, desperately searching the shore for Pordis. She spotted Casper, still sitting on his rock beside the sea, watching the whales.

‘Casper!’ she panted as she stumbled over to him. ‘I need your help.’

‘What is it?’ Casper sprang to his feet.

‘There are people trying to stop me from finding my brother.’ Bianca bent over, leaning on her knees, gulping down air. ‘They tried to trap me. I ran. I don’t know where Pordis went.’

‘Did you find Finn?’

Bianca shook her head. ‘He’s not in Winterton.’

‘Where is he?’

Bianca pointed to the far-off fortress, and Casper’s eyes grew wide.

‘Pordis!’ Bianca cried, as the reindeer finally appeared on the beach.

‘My Bianca!’

Pordis raced towards her, and Bianca fell to her knees in front of her companion, wrapping her arms round her neck and rubbing her forehead against the reindeer’s long snout.

‘Are you all right, my Pordis?’

‘The boy and the girl chased me across the field of snow. Then, suddenly, they stopped and turned back.’

‘Clever Pordis. They must’ve known they’d never catch you,’ Bianca said, getting to her feet. ‘Did you see anyone near the path when you came down to the cove?’

‘No one.’

‘Monodon says you shouldn’t go to the palace,’ Casper said. ‘He says it’s dangerous. There’s something terrible in Snow Haven. Something dying.’

‘Snow Haven?’

‘That’s what the fortress is called.’

‘I don’t care if there’s a deadly monster inside.’ Bianca put her hands on her hips and glared out to sea. ‘If Finn is in there, then I’m going in too.’

‘The path to the palace is long and dangerous.’ Casper pointed up at the rocky cliff. ‘You’ll have to go back through Winterton and out that way.’

Bianca’s heart sank as she looked at the path, which was exposed on all sides. She would be seen approaching the fortress. Even if she could get there, she’d be caught. Her hand went to her heart as she glanced at the sky. The light hadn’t changed since she’d woken up here. How long had it been since she’d arrived? It felt like forever and no time at all. Surely the sun should be setting? Her sense of unease grew as she cast around for a plan. She didn’t know how much time she had.

Casper’s eyes glazed over, then he blinked. ‘There is another way. Monodon and I can take you.’

‘How?’ Bianca looked out to sea, and swallowed. ‘I don’t think I can ride a whale.’

Pordis grunted. ‘I certainly can’t!’

‘You don’t have to. Though you don’t know what you’re missing.’ Casper pointed at a slab of sea ice coming towards them.

Beyond it, Bianca saw the unique counter-clockwise spiralling horn of the narwhal that earned it the nickname, ‘unicorn of the sea’. The whale was black, speckled white, with a powerful tail, small fins and friendly dark eyes.

‘Monodon suggests we climb aboard the ice, and he’ll push us. There’s a landing place, where the penguins fish, at the foot of the cliff.’

‘Us?’

‘You don’t think I’d send you off on an adventure with Monodon on your own, do you?’ Casper grinned, jumping onto the ice raft. ‘Anyway, it sounds like you need all the help you can get.’

‘Oh, thank you!’ Bianca immediately felt stronger with Casper’s support.

‘You’re not leaving me behind,’ Pordis said, walking onto the ice craft and sitting down.

Bianca smiled and stepped aboard. ‘And thank you, Monodon.’ She knelt down, looking at the whale in the water. ‘I won’t forget this. You and Casper are both good friends to help us.’

Swimming under their raft of ice, Monodon propelled the strange sea vessel out of the bay. The intimidatingly pale, spiky fortress was set against the vivid blue sky. As they drew closer, it began to dawn on Bianca how enormous Snow Haven actually was.

How was she going to find her little brother in there? And what was the dangerous creature dying inside?