‘There’s hardly any dripping here.’

‘No.’

‘Why is this hole here then?’

‘There is a source of heat below. Only a little above freezing, but just enough to keep this path open.’

Zole resumed their descent. The shaft was not vertical but slanted with the flow of the ice. Half a dozen times they passed older shafts that had once served as vents but had been drawn too far by the glacier, forcing the heat to create a new escape.

Time lost meaning: repetition stole it away.

When Zole finally dropped a foot or so and landed on raw rock Nona started with shock as if waking from a dream.

‘Where are we?’

‘A temple of the Missing once stood here.’ Zole untied the rope that bound Nona to her. Nona staggered back, almost tripping on the uneven floor, her limbs unresponsive, chest aching.

They had descended the wall of a low-roofed ice cavern with a floor of bare stone. Where the rock lifted it lay scored all across with parallel lines, wounds gouged by the slow passage of glaciers.

Nona took several more steps back, eager to put some distance between herself and the shipheart.

‘Stay close.’ Zole reached out to restrain her. ‘The klaulathu here are many and they are strong.’

‘So, where is this marvel?’ Nona looked around and saw nothing but the dark. The klaulathu’s hatred needled out at her, ancient and hungry.

‘Here,’ Zole said. ‘Where else would it be but beneath the passage its heat has wrought?’

Nona turned and saw what Zole was pointing at. A huge ring lying where the rock dipped. It was three yards across, its perimeter a foot thick and two feet wide. The flat surface had been marked with sigils unlike any Nona had ever seen. Their fierce potential screamed into her eyes, twisting the world around them.

The ring wasn’t bedded in the ground. In places Nona could have slipped an arm between the peculiar crystalline metal and the bedrock beneath.

‘I think …’ Nona stepped closer to the artefact, unable to look away, her gaze anchored by the sigils. ‘Have I seen this before?’

‘I do not know. Have you been to the emperor’s palace?’

‘No.’ Of course she hadn’t been to the palace. She was Nona Grey. A peasant child.

‘That is unfortunate. If you had seen that one then it would have marked you and helped draw you to it. It is unlikely that you have seen another. Although the ice-speakers say that the Missing fashioned one thousand and twenty-four of them and set each within an Ark.’

Nona stood beside the ring now, her hand extended towards it, fingers tingling with the desire to touch the water-beaded metal. ‘What does it do?’

‘It will take you to another such ring. As if you had simply stepped between them.’ Zole joined her and the shipheart’s pressure started the voices chattering again, down in the depths of Nona’s own darkness. ‘Sherzal showed me a drawing of another such ring that stands in her brother’s palace. It lies within the Ark but not within the inner sanctum.’

‘You want us to go to Crucical’s palace?’ Nona raised her eyebrows at the thought of the reception they would get.

‘No.’ Zole gestured for Nona to step into the circle. ‘I want you to go there.’

‘But … me? Alone?’ Nona shook her head at the madness. ‘You’re coming too.’

‘No.’

‘But … what would you do here?’ Nona waved an arm at the cavern. ‘This is crazy.’

‘There are things I need to do on the ice.’ Zole met Nona’s stare. Her face, lit from beneath with violet light, was free of emotion.

‘Things?’ Nona shook her head. ‘No! You belong at Sweet Mercy with us. With your sisters. With me.’

‘I would like to go with you, Nona Grey.’

‘Well, come on then!’

‘But I cannot. I made a promise.’

Nona reached for Zole’s hand. ‘Break it.’ She stepped backwards into the ring hauling on Zole’s arm to bring the girl with her. Zole resisted, bracing a foot against the outside of the ring.

‘I cannot.’

Nona released Zole’s arm and took a step back. ‘It doesn’t matter!’ A bitter laugh burst from her. ‘It doesn’t work.’ She laughed again, amazed at herself for ever believing that it would. A ring that could spit a person hundreds of miles across the world!

‘It requires the power of an Old Stone.’ Zole lifted the shipheart. ‘You must carry it through with you.’

‘And leave you in this place! At the bottom of a hole two miles deep? Now I know you’re crazy. The shipheart has broken your mind.’

‘You must focus on the distance and direction that you wish to travel.’ Zole carried on as if Nona hadn’t spoken. ‘It is that direction.’ She pointed. ‘Otherwise there is a possibility you will emerge from another more distant ring.’

‘Zole! Come home with me.’ Nona’s voice caught in her throat. The hardships of the journey, and being constantly caught between the mind-tearing power of the shipheart on one side, the invading malice of the klaulathu on the other, had left her weak, awash with broken emotion.

‘I want to,’ Zole said, her voice low.

‘Who did you promise?’ Nona took another step back. An idea blossomed within her skull repeated by voices that were hers and yet not hers. ‘Yisht was there to steal the shipheart … She was from your tribe!’ Nona had seen it when she saw Zole and Tarkax together with their companions, but she hadn’t understood it, not until this moment. They all had the same look. ‘Yisht was from your tribe … neither of you was working for Sherzal. Not really. You were both working for the tribe. To open the Ark whichever way you could!’ Nona stopped dead and tilted her head, staring at Zole as if she could tear the truth from her with the power of her will. ‘Hessa? Hessa was a price worth paying?’

‘I never intended for—’

An awful conviction seized Nona and in that moment she didn’t care whether it sprang from reason or from the devils of the Missing. ‘Who is Yisht to you? Cousin? Older sister? Mother …’

‘I—’

‘Whose promise is it that’s keeping you here?’ Nona was shouting. What dark vow would have Zole remain in this unholy place and see her scale two miles of black ice to begin a trek into the awful wilderness above? ‘Whose promise?’

‘I cannot say—’

‘Whose promise, sister?’ Nona put every ounce of her marjal skill behind the question to compel an answer, an effort so fierce that it even quietened the strange voices in her mind.

‘Abbess Glass. I promised Abbess Glass.’

And with that Zole threw the shipheart at Nona, hard, fast, straight and true. All around her the ring’s sigils lit with an ancient light. And Nona was falling, and though she clung to the moment she couldn’t save herself.

Without the passage of enough time for her heart to take a beat Nona stumbled through a free-standing metal ring. She stepped into a limestone cave, with the shipheart dropping from the hand she had used to ward it away. On every side the air was filled with broken flowstone, fragments tumbling lazily away, blasted from the ring that they had coated. And for the first time in an age Nona knew exactly where she was.