Ujurak wrinkled his nose. ‘The water doesn’t taste very nice,’ he commented, licking droplets from his muzzle.

Kallik snorted. ‘You don’t have to drink it!’

Gradually they veered inland, heading back towards the hills, stopping where the pebbly beach gave way to scrub so they could strip a thornbush of its berries. Halfway through her second mouthful, Lusa realised she could hear a tremendous rattling and clacking coming from beyond the ridge.

‘What’s that?’ Kallik barked.

‘Let’s go and see!’ Ujurak bounded ahead, halting at the top of the slope. ‘Look!’ he exclaimed as Lusa and Kallik scrambled up beside him.

Lusa stared down into the next valley at the moving river of caribou, massed so close together that she could hardly see the ground they were walking on. The loud rattling was coming from their feet as they headed away from the coast, many times louder and faster than the rattling from the lazily ambling caribou they’d seen the day before.

‘Where are they all going?’ Kallik asked, putting her head on one side. ‘There’s nothing chasing them.’

Lusa shrugged. She had no idea what could have prompted the herd to move off all together like this. Did they feel Ujurak’s urge to travel, or the powerful pull that was drawing Kallik back to the ice?

‘Toklo will be disappointed,’ she said. ‘He wanted to hunt them.’

While she was speaking, she spotted a flat-face den at one side of the valley. It was built of tree trunks, and it blended so well into the landscape that Lusa hadn’t noticed it until now. Her heart began to race. She gave Kallik a nudge with her snout. ‘Look over there.’

Kallik’s eyes stretched wide with dismay. ‘That’s a flat-face den! There aren’t supposed to be any flat-faces here.’

Looking more closely, Lusa spotted flat-face pelts strung on a line at one side of the den, and a wisp of smoke coming from a round thing like a tree stump on the roof.

‘There’s something odd . . .’ she muttered.

Snuffing the air, she figured out what was different about this den. There was no smell of BlackPaths around it, or the heavy scent of the flowers flat-faces grew in their gardens. The den didn’t just blend into the valley because it was made from tree trunks; it didn’t even have a distinctive flat-face scent. ‘Maybe these flat-faces aren’t dangerous,’ Ujurak suggested hopefully.

‘Aren’t flat-faces always dangerous?’ Kallik huffed.

As they stood peering down at the den, the door was flung wide and a young flat-face cub burst into the open. He was pointing at the caribou herd and yelling something in a high-pitched voice. An older female flat-face followed the cub outside, along with a broad-shouldered flat-face male. All three of them wore pelts made of the same grey-brown fur as the caribou; the little cub had a brightly coloured pelt on his head.