The others followed him, still joined to each other by rope. They ran down a steep, narrow ridge with a sheer drop into the mists on one side. It zigged and zagged as it descended and looked as though it might carry on like that all the way down the remaining section of mountain, but after a few minutes Fishbone stopped.

‘Here it is!’ he said, pointing to a shallow groove that fell away from the path, down the steep rockface and into the wall of fog. ‘Sit on your packs, lie back and slide!’

With that he lay on his stomach and pushed himself off the pathway, shooting down the smooth furrow like a bullet. In half a blink he was gone, just a cat-sized gap in the mist showing he had ever been there.

‘This isn’t going to be good for my vertigo,’ said Lug. ‘It looks very steep. And very dangerous.’

‘You think everything is dangerous.’ Even so, Liska had grown up on the mountaintops and slithering down a rock when you couldn’t see what was below seemed like an incredibly stupid thing to do.

‘Don’t be silly,’ said Elowen. ‘Look how smooth it is! Generations of kittimews must have used it before, and they were all fine.’

If they’re so fine, Liska thought, where exactly are they? For all they knew, Fishbone could be the only kittimew left. The others could all be lying at the bottom of this slide in a heap of rotten bones.

‘Well, I’m going to give it a go,’ said Elowen. She swung her pack into the stony groove then sat on it, ready to descend into the unknown.

‘Wait!’ Liska shouted. ‘We’re still . . .’ she was about to say ‘tied together’, but Elowen was already gone. The rope around Liska’s waist began to stretch out after her, and she only had a few seconds to jump on to her own pack.

‘Quick, Lug!’ she yelled as the slide funnelled her, heart in her mouth, down into the mist. She felt the rope go tight behind her and then heard a strangled squawk and a thump as Lug was yanked off his feet.

Swishhhh . . . The sound of slithering stone filled Liska’s ears as she sailed through the bank of white fog. She held her breath, staring in wide-eyed horror at the visible patch of mountain in front of her, expecting to see a bottomless drop appear at any moment.

Down, down, she went, although it was impossible to tell how fast or how far she had travelled. All she knew was that the slide lasted for longer than she could have thought possible.

It must go all the way to the bottom of the mou—.