‘Your emperors tried many ways to open their Ark, Nona, for hundreds of years. But do you know the most important thing that they discovered?’

Nona kept silent and waited for Tarkax to answer his own question.

‘They discovered that when you hold a treasure of incalculable value and potential, having it closed to you and beyond use is not the worst thing that can happen. The most dangerous thing that can happen is for someone else to discover, or even just believe that they have discovered, the means to open and use it. Such individuals will gather strength to themselves and seek to take your treasure from you.’

Nona frowned. Zole had wrapped her hand once more and stood silent. ‘So … what are you going to do now?’

‘We’re going to send you home, Nona.’ Tarkax grinned, then raised his sealskin mask as the wind strengthened. ‘There are two marvels that will allow it. The first marvel is a work of the Missing. The second marvel is that it is close enough to reach in a day.’

Nona trudged at the back of the group, her mind racing. Zole walked beside her.

‘You were spying on us? Sweet Mercy took you in! The abbess gave you her protection!’

‘Has Tarkax not taken you in and given you his protection?’ Zole asked. ‘Are you not gathering all the information you can and preparing to share it with Abbess Glass on your return? Does the convent not exist in part to train spies?’

Nona opened then closed her mouth. They walked without speaking for several hours after that. Nona watched the other ice-tribers, trudging with bowed heads to either side of them, three men, two women, and Tarkax, all so swaddled in skins and furs that they resembled great forest bears. Two of them dragged a long, heavily laden sled behind them, sliding along on wooden runners. Nona wondered what the tribes of the deep ice, thousands of miles from the Corridor, built their sleds from. The bones of leviathans hauled from the sea perhaps.

‘Where are we going?’ Nona had really wanted to ask whether they were nearly there yet. Her feet were strangers to her and she wondered whether her toes would have to be cut away when they thawed.

‘To the place from where the black ice flows,’ Zole said.

‘Why?’ Nona had really wanted to say that she didn’t want to go there and that she would rather scale the Grampains naked in an ice-wind.

‘Because there is a wonder buried in that place.’

Nona could have asked what the wonder was, but without that mystery to draw her further she felt her legs would just abandon their duty and leave the task of getting her there to her arms.

It took them until nightfall to reach the long dark streak in the ice and follow it to where it grew darker still and finally turned black before abruptly giving way to white once more. Nona knew from her view while crossing the mountains that the stain looked like a great teardrop from above, the long tail of it running to the Corridor wall miles north of them.

Zole took over the lead as the light failed, the darkness being nothing to her eyes. She halted them in a place where the malice from below was still only a whisper.

‘You and I will go alone, Nona. We should be swift.’

Tarkax and the others huddled as close as they could come to the shipheart and formed a barrier against the wind. Tarkax lowered his frosty mask, revealing a grin. ‘Be strong, niece. And you too, Nona Grey. Be fierce and true, like I am.’ He struck his chest with his gloved fist. ‘Zole is the hope of our people, but there is a hero in you too, girl. I have seen her.’

Nona couldn’t help but grin back though her face ached with the cold. She liked Tarkax despite his boasting. She nodded and made a short bow to the ice-tribers. ‘May the wind be at your backs.’ Sister Rule taught that this was a common blessing on the ice.

‘Hah!’ Tarkax showed all his teeth in a broad smile. ‘War is coming, little Nona. Wars are always coming. You give them hell! Remember that anger. You’ll need it!’ And with that he covered his face and walked away, the others following.

Zole and Nona watched them go, standing in silence while the wind moaned around them. When the swirl of ice at last swallowed Tarkax and his people from view the ice felt a very lonely place indeed.

Nona turned to gaze out across the wasteland where their path would take them. Here and there a crimson star stood reflected in the smoothness of the ice. Before her, though, there were no stars, only a consuming black void. ‘If the focus comes while we’re down there we’ll both drown!’

‘There is no focus here, Nona. We are in my home now.’ Zole walked out into the darkness. A moment later she took the shipheart from her pack and Nona followed its alien light.

‘Walk where I walk,’ Zole said. ‘The ice is rotten in places.’

Nona moved closer, gritting her teeth against the invisible, cold fire of the shipheart. She had always imagined the things to be blazing sources of heat and right now she would love for that to be true. In reality the convent pipes bore sigils where they had passed through the shipheart’s vault and it had been those specially crafted sigils that had converted the radiance into something as commonplace as warmth. If she had the skill Nona would have drawn such sigils on both her boots there and then.

The malice radiating from below grew as the ice darkened around them. It reached her even through the shipheart’s radiance and Nona knew it to be far fiercer than she had experienced before. This was the source, the place where the evils the Missing had purged to obtain their so-called divinity, now leaked back into the world.

‘Here.’ Zole halted in front of a fissure disturbingly similar to the one into which she had fallen during her fight with Yisht. ‘We go down here.’

‘Shouldn’t we fix a rope or something?’ Nona had seen that Tarkax’s companions carried iron spikes, hammers, and long thin ropes of woven sinew. ‘We should have asked—’

‘Their ropes were not long enough.’ Zole pulled a coil of the stuff from beneath her coat. ‘Neither is mine.’

‘If we tied them together we’d have hundreds of—’

‘We are going to the bottom. It is more than two miles.’

‘Oh.’ Nona felt for her knives then remembered that she had left them under the ice. ‘What’s the rope for then?’

‘To tie you to my back. It will be a difficult climb.’

As usual, when Zole said difficult she meant impossible. And as usual she managed anyway. Nona clung to Zole’s back, seeing nothing but Zole’s arms and glimmers where occasional flaws in the ice returned a fraction of the shipheart’s light. Zole had secured her pack across her front, with the shipheart inside and the flap left open to let the glow escape for Nona’s benefit. Despite being tied to Zole, Nona clung on grimly. She became thankful for the rope later after hundreds of yards of descent. Her arms were aching and her mind too fragile this close to the shipheart to worry about whether her hands kept tight hold. Zole made steady progress. Her strength was inhuman and she compelled holds out of the ice as it suited her.

While Zole climbed Nona heard nothing but the sound of her breath and of the ice splintering to answer her needs. Each time Zole rested, a new set of sounds became apparent. A constant groaning, a creaking, sometimes bright and almost metallic, sometimes so deep that Nona felt it only in her chest. The slow river of the ice, flowing endlessly towards the Corridor.