To make it worse, Liska could feel the presence of Thresher behind her, burning into the back of her neck. She didn’t dare look round, knowing it was useless. They couldn’t walk any faster and their enemy was getting closer, closer all the time. Soon, she imagined, they would hear footsteps, the panting of the seeper hounds, the grinding of Thresher’s teeth . . .

Liska risked a peek and saw they were still dots on the tundra. There was time to reach the tree and more. But then what? How would they get past them for the journey home?

Don’t think about it yet, she told herself. Don’t think about how you’ll have to fly away, leaving your friends, leaving Lug to freeze and the others to be torn apart by hounds. Just DON’T THINK.

She concentrated on the tree. On the sound of snow beneath her feet, the icy wind chafing her bare face and neck. How she couldn’t feel her nose or ears, and how Lug’s dead weight was tearing the muscles in her shoulder. She kept her eyes focused on the grey shape of Nammu and just kept on taking step after step after step.

*

Dusk had begun to gather, the wispy clouds on the horizon darkening to violet, when Liska realised they were almost there. She had fallen into a kind of trance, hypnotised by her own footsteps and the strain of carrying Lug. Now they were within a kilometre of Nammu itself.

She stopped dead, staring at the thing she had travelled so far to find, drinking it in with her eyes.

It was smaller than the other trees she had seen, although still at least three times the size of the largest oak. Its bark was a deep stony grey, as if it had been carved out of rock rather than grown. Twisted, wind-tortured branches bent into strange contortions jutted out from it all over. Only a few of its leaves remained, dotted here and there on the odd twig. These were leathery brown and orange. The last leaves of an endless autumn stubbornly clinging on.

The ground around it was dusted with frost, icy crystals creeping over Nammu’s trunk and branches. And behind it was the cause. Crowding in, stretching off into the distance on either side, was a solid wall of blue-and-white ice.

The glacier.

A frozen tsunami, solid and unstoppable. It reminded Liska a bit of the granite walls of the Shield Mountains that surrounded her home. Except this towering mass was moving – too slow to see, too quiet to hear but moving all the same. Inching closer and closer to the sacred tree it would soon envelop and kill.

‘But . . . why hasn’t it swallowed the tree?’ Liska stared closer.

The colossal block of ice seemed to have pushed forwards everywhere except around Nammu. The light tree was sitting in a scoop, as though the glacier was afraid to touch it.