It led them through an arch to an uneven chamber, where wooden planking seemed to have been laid over a sloping, swelling floor. The roof above was so low they had to crawl. Raffi guessed that the floor itself was the roof of some vault or dome below; once he put his hand through a hole and felt nothing but emptiness. The dust was so thick that he made handprints in it, and the lantern, hanging round the Sekoi’s neck, threw wild, swinging shadows.

They crossed three vaults like this, each one more cramped. In the last the roof scraped their backs. Galen slithered to a halt. ‘Where are you taking us?’ he growled.

Ahead, they caught the Sekoi’s grin in a swing of the lantern.

‘Safety lies in secrecy, keeper. You know that.’ It turned and crawled on. Galen gripped his stick and swore.

Finally the Sekoi came to a tiny door in the wall and opened it. ‘If you fear heights,’ its voice said, rather muffled, ‘don’t look down.’

Coming through the door and straightening up with relief, Raffi found himself on a curved balcony; a rail to his left and to his right a wall that glinted here and there. He saw remnants of faces, giant hands, gold, scarlet and blue. Galen caught the Sekoi’s arm roughly.

‘What are these?’ His voice echoed, hissing in far distances.

Impatiently, the Sekoi glared at him, then held the lantern up. ‘Mosaics. Images. Of the Star-people. The ones you call the Makers. This, look, is Flain.’

Galen, astonished, made the gesture of peace; Raffi did the same. In the weak light the enormous face of a man gazed down sternly at them, pieced together from marble, porphyry, precious stones. Parts of it had been hacked out. Staring at the vast eyes, all at once Raffi sensed echoes; lost sense-lines. Turning, he caught hold of the rail and leaned over.

‘Be careful!’ the Sekoi hissed.

The darkness was immense. A gust of wind blew against him; he glimpsed appalling distances, the floor so far below that he gripped the rail tight with cold fingers, feeling the world swing away under him. Dizzy, he hung on.

They were above some vast empty place, once a temple. The wind howled through its shattered windows. In the darkness he made out glimpses of pillars, fallen altars, smashed statues. Awed, Raffi gazed down, feeling Galen beside him.

‘One of ours.’

‘Once.’ The keeper was chilled; the destruction filled him with bitterness.

‘Hurry now.’ The Sekoi tapped their backs. ‘And keep away from the rail. It breaks.’

Tiny in the immense curve of the dome, they followed the star of the lantern, clinging flat to the wall in places where the rail had gone and only emptiness hung. Once, far down in that blackness, something small clattered. The Sekoi whipped its coat over the light; breathless, they waited in the pitch dark.

‘Rats,’ Carys breathed finally.