As the sun rose over the horizon, big and pale and flooding the Groaning Splinters with light, Flint, Blu, Eska and Pebble knelt on a flattened iceberg. The Grey Man strode out into the sea, nudging the iceberg forward, and Flint stifled a yawn. He knew Eska hadn’t noticed him creep out of the igloo in the night, but, if he carried on yawning like this, she’d start to ask questions – and some things were better left unsaid, especially while the Ice Queen’s anthem was going on and Eska’s voice was little more than a wisp of breath.

Flint glanced at Balapan circling above them. ‘She has an unfair advantage in this quest,’ he muttered. ‘Wings make all the difference.’

The Grey Man walked on for a while longer, then he paused before a maze of iced bridges, arches and spiral columns.

‘I’ll leave you here,’ he said. ‘It seems like a perfectly reasonable place.’

‘But we need to get to the furthest of the Groaning Splinters,’ Eska whispered. ‘We’re not even among them yet!’

Flint nodded. ‘It’s not as if the wind is going to carry us on. It’s as calm as a millpond this morning!’

Blu jabbed a little fist in both Eska and Flint’s sides. ‘Listen to giant. He know way.’

The Grey Man smiled at Blu. ‘For someone so small, you’re actually rather wise.’ He stood back from the iceberg. ‘And now for a spot of convenient wind.’

He took a deep breath in and his stone body crunched as his chest swelled, then he bent down, level with the iceberg the children sat on, and let his breath out. The iceberg drifted across the water, steered by the giant’s breath, and the group swung round as they realised what was happening.

‘You’re really not coming with us?’ Flint cried.

The giant’s breath continued to push the iceberg out even though the Grey Man now stood up tall. ‘I cannot stay any longer; there is someone I need to speak with.’ He paused. ‘But you will find the Frost Horn and together you will blow it from the stars.’

Flint wondered whether it would be impolite to point out that the time for overdue catch-ups with friends was probably not now, just hours from the Ice Queen’s dominion over Erkenwald, but there was something in the giant’s eyes as he said goodbye – something kind and honest and wise – and Flint didn’t press the matter further.

‘Thank you,’ Eska whispered.

And, though the sound didn’t reach the giant waving from the shallows, Flint could tell that he knew the shape of those words because he smiled.

The giant’s breath steered the iceberg on towards the Groaning Splinters and, had Flint’s and Eska’s minds not been filled with images of the Ice Queen wiping out the tribes and tearing down the Sky Gods if they failed to find the Frost Horn, they might have marvelled at the spectacle before them – at the spires, domes and caves of glittering blue ice. The iceberg drifted beneath an arch and on towards a row of spiked peaks.

‘Does it seem a bit too quiet to you?’ Flint asked after a while. ‘If you ignore the Ice Queen’s anthem . . .’

He listened for the cries of the birds from the cliffs, but there was nothing now. He looked back towards the flatter icebergs where the seals had been resting. They were gone, too . . . The iceberg glided on and Flint watched Balapan dipping low between the Groaning Splinters as if, perhaps, she had seen something. He reached for his Anything Knife and Eska gripped her quiver.

Then a sloping brown head slid above the surface in front of the iceberg the group huddled on. Amber eyes, whiskers curling from a dark wet nose and two sharp white tusks hanging either side of a drooping mouth. One by one, more brown heads appeared until they surrounded the iceberg in a dark circle.

Flint swallowed. ‘Walruses.’

The giant’s breath nudged the iceberg forward, but the largest of the walruses lifted its blubbery body out of the water a fraction more until it blocked the path through and the iceberg ground to a halt.

‘They’ll let us past, won’t they?’ Eska whispered.

But, when the largest walrus shook his blubber and let out a juddering roar, Flint knew these were not ordinary walruses. Like the wolves back on the Driftlands, these were now brutes cursed to obey the Ice Queen.

Flint fumbled with his knife as a walrus thumped its enormous body on to the ice and stabbed at the children with its tusks. Blu screamed and Flint jammed his boot into its head then, as it reared backwards, Eska sent her arrow into its blubber. The walrus sank out of sight, but the others drew closer.

‘Have you got an invention in your bag that can help us?’ Eska gasped.

Flint’s eyes widened as he remembered he had left his rucksack back in the igloo. The Grey Man had warned against extra weight on the ice and Flint hadn’t wanted to lose the snow-goose feathers he’d carried this far in the depths of the icy sea. He brandished his Anything Knife as another walrus shunted its hideous body against their iceberg, then Balapan dive-bombed the beast and it drew back for a second.

‘They’re trying to topple the iceberg!’ Flint cried.

He pulled Blu behind him and plunged his Anything Knife into the neck of a walrus whose tusks were just centimetres from Eska’s leg. The beast let out a low grunt-whine, then it vanished beneath the surface.

The air shook with the Ice Queen’s anthem and the roars of the walruses as they hacked the iceberg with their tusks, clawing closer to their prey, but Flint and Eska were in the hunt now, their aim sure, their weapons poised to kill, and Balapan was wielding her wings and talons above anything that came close to Blu.

Before long, just one walrus remained. The largest of the herd. It disappeared beneath the surface and when Flint glanced down he could see only the water and the undersides of turquoise icebergs.

‘Has it gone?’ Eska whispered.

The quietness dragged on and Flint lowered his knife, then there was an almighty boom from beneath as the walrus thrust its weight into the middle of the iceberg. It juddered. It groaned. And Flint’s eyes widened.

Then it crunched in two, Flint and Blu on one side – and Eska on the other.

The walrus slid through the water towards the iceberg that Flint and Blu were stranded on and, though Balapan hurtled down to try and distract it, the walrus merely batted the eagle away and, narrowing its yellow eyes, made a beeline for the iceberg.

‘Keep going!’ Flint yelled to Eska. ‘Use your bow as an oar until you reach the furthest of the Groaning Splinters! Then find the Frost Horn!’

The walrus slashed its tusks into the ice by Blu’s boot and when Flint wrenched his little sister away he looked up to see Eska frantically trying to paddle towards them. Flint brandished his knife and the walrus held back for a moment.

‘Turn round and keep going!’ he shouted again. ‘This is your chance, Eska – I can fight the walrus!’

For a second, Flint saw Eska falter, then she turned her terror-stricken face away and inched towards the last of the Groaning Splinters before the wide stretches of ocean.

Flint took a deep breath, then he turned back to face the walrus.