The roof was barely visible in the candlelight. But Nelo, squinting, made out the latticework of iron strips that held the panes in place, and the panes themselves grey with snow. And there, yes, in the centre, he saw a spiderweb of cracks.

‘I don’t know what’s holding it up,’ Mago said. ‘If one pane fails—’

‘The rest will follow.’

‘It’s just like that accursed awning again.’ He shook Nelo’s shoulder. ‘Come on, Northlander. These are your people. Make them listen!’

And then another pane cracked, more loudly. All around them people looked up.

Nelo dropped his blankets and ran to Ywa. His urgency finally got through. She barked out commands, and with impressive speed the evacuation of the makeshift hospital began. All the doors were flung open, including the big ceremonial entrance through which the Annids would process into the room for the Water Council meetings and other great occasions of state. Soon folk were streaming out into the corridors outside, tunnels dug through the ancient growstone of the Wall.

Then that first pane collapsed. A column of snow fell vertically, with a tinkle of glass from the window fragments that came with it. Around the Hall people stopped what they were doing and peered up at the roof. More panes cracked and failed, dumping more snow. Then the iron structure as a whole started to sag like a bulging, overloaded net. As the frames holding them distorted out of shape, more panes shattered with brief pops, and glass and snow showered. As Mago had suggested, Nelo saw, once one pane failed the integrity of the roof as a whole was lost. People, wary, backed off towards the walls.

The roof gave way completely. Amid a hail of glass and bits of iron the snow roared down in a single massive load, falling all at once. People screamed, and ran if they could, but many were overwhelmed by the snowfall as it covered the pallets and operating tables and heaps of blankets and medicine chests. It even washed into the fires in the old hearths, dousing them immediately, Nelo saw.

It was over in a moment. Then came the first groans, the first cries for help. Nelo hurled himself into the drift, digging with his bare hands.

Fresh snow fell, the flakes gliding down from the sky and through the smashed roof, visible in the dim light of the surviving lanterns, fresh snow still falling thick after all these hours and settling on the heaped masses on the floor.

Too fast, Alxa thought. After half the night not moving at all, now we’re going too fast.

Anxious, bundled up, she peered out of the window of her cabin. She could see nothing but flakes of snow, still falling, in the light of her candle. The door was admitting a chill draught, even though she’d tried to stop up the cracks with bits of her own clothing. She had no idea where they were. On the Wall, of course, but the Wall spanned the whole northern coast of Northland. She had no idea how close to Etxelur itself she was, how close to home.