For a moment, Flint did nothing at all. He just stared at the girl in front of him. Her body was almost blue from the chill, but she wasn’t shivering. She was absolutely still, like a doll. Only her face seemed alive.

‘Turn the key in the pedestal. Three turns to the right and half a turn left.’

Flint frowned. The girl’s voice was hoarse, and weak, but there was something strangely magnetic about it and, despite the dangers all around him, he found himself drawn to her words.

‘Please,’ the girl begged. ‘It will undo the spell.’

Shaking himself, Flint gathered his rope into his rucksack, slipped off his crampons and dropped down into the hall; he couldn’t risk being seen by the Tusk guards. But still he said nothing. Who was this girl? Flint’s mind raced as he took in her shock of red hair. The Tusks were blond, the Furs had brown hair and the Feathers had hair the colour of midnight. This girl didn’t fit. But those eyes – big and bright and blue – brought back memories of the Tusk spies Flint had seen in the forest last month. And, if this girl was a Tusk spy, he wasn’t getting mixed up with her. Not when he had a rescue mission ahead of him.

He took a step into the hall and felt Pebble tense inside his hood. The fox pup’s ears were trained to sounds most humans missed and Flint listened hard until he, too, could make out a faint tapping noise, like metal clanging, from deeper within the palace.

The girl blinked frightened eyes at Flint. ‘Please,’ she said again. ‘There isn’t much time.’

Despite the pull of her voice, Flint took a few more nervous steps over the ice-crusted floor: past the organ in the middle of the room, below the chandelier spread with candles that burned with bright blue flames, and on towards the silver trees and the doorway leading further into the palace. Somewhere beyond that door was his ma.

‘I know I don’t look or sound like much,’ the girl whispered from behind him, ‘but for some reason the Ice Queen thinks my voice is important.’

Flint kept walking, but his ears snagged on those last words because with every sentence this girl uttered he could feel himself being folded further into her story. Her voice, whether he liked it or not, did seem to hold some quiet sort of power.

‘I know things from being locked up here in the palace,’ she went on, ‘and if you set me free I can help you find whoever you’ve come for.’

The girl stifled a sob and Flint recognised something in her then: something desperate, despite her stillness, like the beating fear in the eyes of a wounded animal. And it was harder to keep walking than he had expected.

He threw a glance over his shoulder. ‘What’s your name?’

‘Eska.’

‘And your tribe?’

There were tears standing in Eska’s eyes now. ‘I – I don’t remember a tribe. The Ice Queen took my memories when she locked me in this music box.’

‘Everyone belongs to a tribe.’ Flint looked her up and down and the hardness closed back around him. ‘Tusk probably – we all know the only reason Tusk children roam without fear is because they’re the Ice Queen’s spies and their parents are her guards.’

He turned away and concentrated on the hall. It was ‘detours’ like this – a term his parents had come up with for the distracted, almost sideways nature of his adventures – that always got him into such a mess. And these detours were the reason Tomkin had carved the words Decide Where You’re Going And Go There on the runners of his sled. The trouble was, Flint realised as he tiptoed over the ice, he usually only discovered where he was going halfway through a journey, and when he arrived he was often somewhere he hadn’t intended to be. But this was a journey to bring back his ma and he wasn’t going to let a stranger who didn’t even know her tribe get in the way of that.

He took a few more steps across the room, mumbling to himself as he went. ‘Stupid Tusk spy . . .’

But even as he said the words he knew they weren’t true. This girl was afraid – really afraid – and Flint had done enough hunting to know what fear looked like. What if she really was the Ice Queen’s prisoner and knew things Tomkin needed to hear to stage his rebellion? Flint dug his nails into his hands. He could sense there was something more to the girl than what he was seeing . . .

‘Find Ma first,’ he murmured.

Pebble, though, had other ideas. Wriggling free from Flint’s hood, the fox pup dropped down to the ground and ran up to the pedestal.

‘Pebble,’ Flint hissed. ‘We need to go.’

But the fox pup was clambering on to the pedestal now and Flint watched, open-mouthed, as Pebble raised a tentative paw towards Eska. The little animal was usually cautious and untrusting around those he didn’t know and yet with Eska he didn’t seem afraid. Flint watched as Pebble rubbed his body against the girl’s dress and then licked her ice-cold toes before turning to Flint and making a quiet huffing sound.

‘We don’t even know what tribe she’s from, Pebble. Even if she’s not working for the Ice Queen, she could be dangerous.’ He glanced across the hall towards the door between the silver trees. ‘Come on.’

But the fox pup wove between Eska’s legs and turned his twitching nose back to Flint. The boy grimaced. Tomkin had reminded him only the day before about harnessing the mind of a warrior: becoming silent, focused and deadly. He cursed under his breath. What he was about to do was not focused, and it was decidedly undeadly.

He hurried back to the pedestal and placed a hand on the jet-black key.

Eska’s eyes glittered and, though her words were faint, she repeated her plea. ‘Three turns to the right then half a turn left.’

Flint shot Pebble a withering look. ‘It’s your fault if this all goes wrong.’

Pebble flicked his tail defiantly, then Flint’s mitten closed round the key and he turned it, just the way Eska had said. For a few seconds, there was a grinding sound, like musical notes draining away, then there was a click as the key finally rotated left.

Eska slumped on to the pedestal and for a moment Flint wondered whether he’d killed the girl. A death on top of a detour would be hard to explain to Tomkin. But then slowly, shakily, Eska raised her head. She looked at her hands first, turning them this way and that as if she couldn’t believe they belonged to her. And then she flexed her toes.

‘Thank you!’ she gasped. ‘Thank you!’

But, as she struggled to her feet, the whispers began. Flint jerked his head upwards. They were coming from the blue candles flickering in the chandelier.

Come to the hall, the candles have spoken.

The curse on the child has now been broken!

Again and again the flames whispered and Flint’s blood curdled. He scooped Pebble up into his hood, then turned to Eska.

‘You didn’t tell me the candles were spies!’

Eska staggered off the pedestal, then fell to her knees under the strain of using muscles so long locked under a spell. She scrabbled for the wall and hauled herself up.

‘I – I didn’t know,’ she stammered. And then her voice grew harder and she glanced at the arches. ‘We have to leave.’

Flint’s jaw stiffened. ‘I’m here to free my ma and you’re going to show me how I get through this palace to the ice towers, like you promised.’