Nina cast her light over the walls as she moved down the short passage. It intersected with a curving corridor. From its arc, she guessed it ran around the whole interior of the ship/fortress/whatever the hell it was. She settled on ‘fortress’ until seeing proof of anything else, still unwilling to give Eddie any points for his alien spaceship theory. The angle at which it was trapped meant the route to the right dropped steeply downwards, the floor more like a slide. It might be traversable without ropes, but she didn’t fancy trying it.

She aimed her light upwards, to the left. The other direction curved inwards around the structure’s centre, disappearing beyond a corner. Doorways lurked in the darkness. ‘That way’ll be easier,’ she said. ‘Looks like there are other rooms leading off it.’

‘Space alien bedrooms, probably. But you’re right,’ Eddie went on before Nina could make another weary protest. ‘One slip going the other way and we’ll be whizzing down to the front of the ship on our arses.’ He took off his helmet and crampons, the others following suit. ‘If we jump across the corridor, we can use those ribs in the other wall like steps to go up.’

He readied himself, then made a running jump across to the inner wall. A tense moment as one foot slipped from the protruding crystal rib, but he caught himself and began to ascend. His progress became easier as he followed the corridor around, the wall’s curve making the climb progressively less steep.

Nina vaulted after him and followed him to the first opening. ‘What do you see?’

‘There’s a room here,’ he said, aiming his light through the towering doorway. ‘Full of benches – or could be beds, actually. If they are, whoever slept on ’em was tall.’

‘Like the Veteres,’ she said quietly. She aimed her light into the next room. The beam reflected back at her, and not off crystal. ‘There’s ice in there!’ While the passages they had traversed so far had remained strangely free of frost, the room’s rear wall had a thick translucent coating.

Eddie brought his light down to the floor of the chamber. ‘Looks like it’s been ripped open.’ The metal was buckled, ragged tears disappearing into the icy wall. ‘Or crushed. A hundred thousand years of ice must weigh a fair bit.’

‘Yeah.’ Noises from behind made her turn. ‘Oh, you might want to help Cheng before he goes down the world’s scariest Slip ’n’ Slide.’

Imka had jumped after the couple, but Cheng was hesitating at the end of the entrance passage. ‘I’m okay,’ he protested. ‘I can do it.’

‘Well, let’s make sure of that, shall we?’ said Eddie, returning and extending his arms to catch him. ‘Come on, kid.’