‘Irene?’ he said. His voice was deep and organ-toned, though still recognizably Kai’s, and it hummed in her bones. The floor seemed to shudder in response.

She gathered herself. ‘Yes,’ she said. ‘Are you – all right?’ It was a stupid question, she knew, but it was difficult to know what one should say. Etiquette on dealing with apprentices after they have turned into dragons – another missing item from the Big Book of Library Procedures.

‘Absolutely,’ he rumbled. ‘This place is quite congenial to me. Stay back while I bring down the roof.’

Well, the world was on the more lawful side of things, rather than on the chaotic end of the universe. The ruling despotic regime was an unfortunate side-effect of that. As were the guards and guillotines. It would explain why Kai had no problems with being a full dragon here. In a more chaotic alternate world, which they’d unwillingly visited before, he’d been barely conscious in human form, and it would have been much worse if he’d been in dragon shape.

Kai reared up, his wings spreading till they bent against the walls, and set his back against the ceiling. The floor creaked ominously beneath him, but it was drowned out by the groaning of the ceiling as he shoved against it. Tiles came loose, falling to shatter against the floor, and through the dust and the increasing smoke Irene could see the remaining plaster cracking and falling away, and the central rafters bending.

‘Is anyone up there?’ came a yell in French from downstairs.

The natural human response was to shout, ‘No!’ Which said something about humanity. But Irene was too busy watching Kai, in any case, and trying to stay back, as more and more of the ceiling and roof came tumbling down.

With a heavier crash, the floor began to give way. Kai flexed his body, shifting to brace himself against the walls of the building, and lowered his great head. ‘Irene, get on me, between my shoulders – now!’

It would be bad manners to argue with the designated driver. Irene unslung her rifle and dropped it, then scrambled on top of the nearest bit of Kai’s back, crawling up between his shoulders. It felt horribly lese-majesty and improper to be crawling on all fours along the back of a dragon like this. His skin was like warm flexible steel, rippling beneath her hands as his body flexed to hold him in position, and, now that she was on top of him, Irene could smell the sea, stronger than the stench of dust and mould and fire.

Another piece of floor went tumbling. Fire came streaming up from below, leaping in the sudden burst of air, and Irene flung herself flat on Kai’s back, her hands digging in as best they could. He was too broad for her to straddle, so she plastered herself against him and prayed. ‘Go go go!’ she shouted. ‘Just go!’

Kai flung himself upwards in a twisting curve, scraping through the gaping hole in the roof, his tail lashing behind him as he rose into the air. Irene clung to his back, her face pressed against his hide, and felt his body flex underneath her in the sort of S-bend that should have been impossible – that would have been impossible for a natural creature flying naturally.

But Kai was a dragon. He rose through the air as if he was simply moving from point A to point B like a painting on a scroll, and though his wings spread out in great blue arches as if to catch the wind, he flew against it. Irene could hear the screams and shouts from below, and the sharp cracks of rifle shots, but Kai’s pace didn’t falter as he drifted further and further up, till the city lay spread out beneath them like a photograph and the burning house was a distant blotch of orange.

‘Irene?’ He didn’t turn his head to look at her. His flight path changed to a curving hover, tracing a wide circle in the air. ‘If I hold steady now, can you get a little closer to my shoulders? It’ll be safer there for you, when we pass between worlds.’

‘Give me a moment,’ Irene said through gritted teeth. It helped if she kept her eyes on Kai’s back, rather than looking down at the ground beneath. She wasn’t fond of heights at the best of times, and sitting on a dragon’s back hundreds of yards in the air made it hard to ignore exactly how high up she was. However, one consolation was that she wasn’t being as wind-blown as she’d expected. Something was blunting the effect of the speed and the air currents on her – and on Kai too, presumably. It must be to do with the whole dragon magical-flight thing. She added it to her list of questions for later, as she pulled herself slowly along Kai’s back to between his wings.

‘Now sit upright.’ She could hear the amusement in his voice.

‘Like hell,’ Irene said. It was a very long way down.

‘You’ll be safe. We’ve carried people before, Irene. Sages, visitors, human favourites . . . Trust me. I won’t drop you.’

It’s not a question of me not trusting you. It’s a question of whether or not I can make myself physically let go of my death grip on you. Finger by finger, Irene released her hold on Kai’s hide and pushed herself to a sitting position. Kai was too wide for her to sit astride, so she curled her legs underneath herself. Tendrils of mane flowed back from around his head, and she tentatively held onto a couple of them. It wasn’t logical, but she felt much better for holding onto something. ‘What now?’ she asked.

‘Now I travel back to Vale’s world.’ Kai’s wings flexed, spreading to their full extent. The light glittered on them like the water on the surface of waves. ‘I know its place among the flow of the worlds, and I could fly to Vale himself, if I so desired. But he probably wouldn’t like that,’ he said, abruptly losing his formality. ‘Where should we go?’