Osidian pulled him away.

'What…?' Carnelian said, pointing at the fretted wall.

Ammonite arrays, signed Osidian's hand. Calculating the approach of the Rains.

They passed one of the bridges, a simple arch without a parapet only wide enough for a single man. It crossed over to a postern gate sunk deep into the heart-stone wall.

Carnelian glanced up and saw, high above the gate, a few isolated holes that might have been windows. It was like a fortress or a prison.

He pulled Osidian's sleeve. He pointed at the gate. Where does that go? he signed.

The forbidden house.

Carnelian stared up at the windows and then pulled his cowl down and held it tight over his face by pressing his chin into his chest. He had a silly fear that Ykoriana might be up there looking down.

They went along the ravine edge as it widened to sky. Carnelian glimpsed the blue spread of the crater and then he saw Osidian had found some cracked ledges that led down into the ravine and begun to descend. Carnelian peered down to where its sheer edges were snagging morning light. For the first time he considered the reality of where they were going. He remembered the long climb of the Rainbow Stair, and that Osidian had described this Ladder as being harrowing. He shrugged. There was no turning back now. Chewing his lip, Carnelian started down the precarious steps.

The ravine squeezed down to a narrow cleft. The steps continued out through its end seemingly into the sky. Osidian had wedged himself between the walls. His cloak flapped desperately in the wind as he scrunched it into a ball and trapped it between the small of his back and the rock. He swung his pack round into his embrace and inserted his hand into it. He looked away with narrowed eyes as he rummaged. With a triumphant grin, he brought forth ajar that he gave to Carnelian, who could only look at it. Osidian fished out another. Carnelian watched his friend open the jar then pull up the corner of his robe and run it round inside. It came out white and oily. Osidian bent his knee to bring his foot towards him, leaned over and began to rub it with the paint. After a few strokes he looked up, holding his foot with one hand, the robe's whitened corner with the other.

'Are you just going to stand there watching?' he cried over the wind.

'Are we going barefoot?' Carnelian accented his words with gesture.

'Naked feet provide suction as well as a sensitivity to the movements in the rock.' Osidian resumed the daubing of his feet.

Carnelian wriggled himself into a stable position. Tentatively, he lifted one foot and kneaded his toes, rubbing dust from between them. 'And the paint?' he shouted.

'It will not come off. It will protect the paleness of your feet.'

Carnelian dipped a corner of his robe into his jar and rubbed some on. The paint reeked of turpentine. It was sticky and gleaned coldness from the wind. He began to apply it over his foot up to the ankle.

Take it higher, at least up to your knees.' Osidian hoisted the skirt of his robe. His long strong legs were so white they made the paint seem yellow.

When his feet were done, Carnelian began to spread the stuff up his legs.

'It is only paint,' cried Osidian, grinning. 'By your face one would think it was dung.' He made a lunge with the corner of his robe. Carnelian grazed his arm trying to dodge it, but it landed anyway. 'You had missed a bit,' said Osidian. 'Now do the soles.' He folded his feet up one at a time as he painted them. When each was done he waved it in the wind to dry.

'You look ridiculous.'

Osidian's eyebrows rose, making Carnelian look at himself. They both laughed. Osidian touched his foot gingerly to the floor as if he feared the paint might glue him to the rock. When he was standing firmly on both feet, he began to wriggle out of his robes.

Carnelian stared in amazement as Osidian pulled layer after layer over his head and pushed them under his feet. The last two robes were merely a mist concealing his body. Soon, he was dazzling, naked against the rock. Carnelian looked away.

'You too,' cried Osidian, through chattering teeth.

Carnelian tried to turn his back on him but the effort threatened to tumble him into the crack of the ravine. He cursed as he began to struggle out of his robes. He winced when his elbow struck rock. 'Is this really necessary?' he cried.

Osidian jabbed a finger out towards the sky. 'Out there, these robes would make us kites.'

'Could you not have found a better place to change?'

'Would my Lord prefer to expose himself above to the eyes of the forbidden house?'

Carnelian grumbled. He turned when he was wearing only a single robe. It was almost transparent. He could see his pimpled legs and the dull, discolouring paint. 'It is cold. Perhaps I should keep this on.'

Osidian made a face at him. 'I promise you that feeling the cold will be the least of your problems. Take it off.'

Carnelian pulled the last robe over his head. Osidian was looking at him. Carnelian blushed. Osidian pulled neatly folded bundles out of his pack and threw them at Carnelian. They turned out to be a padded tunic and close-fitting trousers. He put them on as quickly as he could. This is hardly the attire of the Chosen.'

Osidian flashed a smile and then shouldered the pack.

They stepped out of the ravine into a blinding churn of wind and sun. Carnelian clung to its cracked lip until he could see again. He clung harder when he realized how narrow was the shelf they stood on. Beyond was a world of air remotely floored by the turquoises of the crater. The ground was impossibly far away. His fingers tried to force their way into the rock to anchor him.

'How long will it take us to go down?' he shouted, stunned. He looked up when there was no answer. Osidian was standing away from the rock leaning into the wind with his back to him, his head up and very still. Carnelian released his hold and carefully moved to his side. The wind roared in his ears. Osidian looked so solid that he had to fight a desire to grab hold of him. Osidian's eyes were piercing the south-west. Carnelian shaded his eyes and squinted. Dazzling blue sparked off to a dip in the Sacred Wall. Above, the pearl sky tainted darker.

'What is it?' cried Carnelian, swallowing wind.

'Rain,' cried Osidian, not looking round.

Carnelian looked again. It made him remember his father organizing the Rebirth. What if his father had need of him? He put the thought out of his head. He had made his decision.

Osidian was saying something. Carnelian turned and saw him mouthing sounds. He shook his head and pointed to his ears. Osidian took him by the shoulders and leaned in towards him. 'Do not worry. We have time.' Carnelian felt Osidian's lips brush his face and was aware of the hands gripping his shoulders. 'It is still more than ten days away,' said Osidian in his ear.

As he was released, Carnelian put his hand up to stop the warmth of Osidian's breath from escaping. Slowly he relaxed the tension in his other hand and, daring to trust to the wind, braced himself against it to look down. He mastered his terror of that airy gulf. He was more determined than ever to follow Osidian down, whatever the consequences.

The steps were cracked, treacherous with scree, an uneven, narrow flight ablaze in the sun. On one side rose a chaotically jointed wall of slabs. On the other, a vision of falling. It was a height vast enough to daunt a hawk.

Carnelian felt Osidian looking at him and saw that he was frowning. We had better go back, he signed. The wind is too violent.

I do not fear, signed Carnelian, with shaky hands.

You are still weak from the sky sickness.

That was days ago.

The wind, the sun-

/ am fine, chopped Carnelian. He pointed at the steps. / will go first. I do not want to take you with me if I fall.