‘They will all soon be with us.’ He glanced up to the spiral’s top. ‘Zan is preparing the machine – under guard, of course. I do not trust him.’

‘A traitor can never be trusted,’ she agreed. ‘I will be glad when we no longer need him.’

‘As will I. Is everything prepared here?’

‘It is.’ She indicated a shallow recess beside the portal. ‘The resurrection key will open the door – once the gas inside has been removed. Come, look.’ She led him to the ledge’s side. ‘Down there – do you see the pools?’ Light shimmered off pockets of water lower down the red cliffs. ‘The gas will flow down through lead pipes into the water and become harmless. When it has all gone, the door will open.’

Gadreel turned back to the entrance. ‘Our persecutors were very clever,’ he mused. ‘If they had applied that cleverness to weapons, they might still be here.’

‘But we would not.’ Sidona returned to the portal, producing the key from her robes. ‘Be thankful they considered themselves too civilised for war.’

He smiled. ‘Indeed. Then begin. Bring our people back to life!’

She placed the key into the recess. It clung to the glassy surface as if magnetised. She closed her eyes and placed her palm upon it.

A low rumble slowly rose in volume. ‘It begins,’ Sidona proclaimed. ‘The gas is being drawn from the chamber.’

Gadreel turned to the portal. There was a faint yellow tinge to what lay beyond; the room was filled with the same gas as the sarcophagi. As he watched, the colour gradually disappeared, as if draining out through the floor.

Before long, it was gone. ‘It is safe,’ said Sidona. ‘I can open the door.’

She did nothing physically, but Gadreel knew she was reaching out with her mind. The rumbling faded – then the door started to open, slowly rising upwards.

He pulled her back as residual wisps of gas curled from the widening gap, but they dispersed in moments. The barrier continued to rise. Gadreel held his breath, waiting for his first view of what awaited within . . .

Both he and Sidona were left briefly speechless by the terrible yet incredible sight. Finally, he spoke. ‘We have found them. They are here!’

His wife took the key. ‘I will wake them.’

‘Wait.’ She stared at him, demanding an explanation. ‘Summon Maseen – any priestess can bring them from their sleep. I need you for something more.’ He looked up the spiralling walkway. ‘Our enemies of old are gone. But we have new ones – powerful ones.’ His expression turned cold. ‘Come. We will use the humans’ machine to destroy them!’

‘There’s another split coming up,’ said Nina. ‘Which way do we go?’

The main passage continued its descent, but another angled off it, heading slightly upwards. Eddie and Barney examined scuffed dust on the floor. ‘Most of them went down,’ said the Australian.

‘Only most of them?’ Cheng said, regarding the other tunnel nervously.