In some versions of Krakow there would have been a huge central railway station, but here there was a grand travel-hub building with sleighs being constantly flown in and out. They were drawn by reindeer and horses that galloped through the air. It was a more obtrusive use of magic than Irene had seen elsewhere in the city – which, come to think of it, seemed generally worn down. The place desperately needed some renovation, which suggested a financial depression. The whole situation was probably linked to the general uncertainty in this world’s Russian Empire and to the rigid state control of magic. Irene noted it as background detail, considering how it would impact on their mission, in the same way that she would have studied the grammar and vocabulary of a new language.

Fortunately the guards at the gates didn’t ask for passports, but the tickets were expensive enough that Irene winced for her dwindling finances. A pageboy who cast sideways glances at their cheap clothing led her and Kai to a sleek black-and-silver sleigh with six large reindeer fastened to it. He opened the small side door and bowed them inside. It was crowded: there was barely room for them to squeeze into a corner, and everyone else was better dressed than they were. She spotted bright clusters of ribbons on sleeves and at throats, or smooth sable gloves and high-heeled red leather boots.

‘Good evening,’ the woman sitting next to her said brightly in Polish. She was the rich elderly type, with furs that showed their age but had once been very expensive. Her rouged cheeks matched a red nose. ‘How nice to have young company on this overnight flight! What brings you on this trip?’

Kai smiled in polite incomprehension. Irene was left to carry the conversation and the cover story, which at least took her mind off the sleigh rising into the air and the heights it reached. And the speed. Zeppelins or high-technology shuttles were so much better than this sort of transport. One could shut the windows and didn’t have to see the landscape below spooling past at an impossibly fast rate, from far too high up. She concentrated on making her narrative sound convincing.

‘. . . and so my cousin here came to get me after my mother’s heart attack,’ she concluded. It was a tragic tale of family illness and breakdown, complete with a father’s alcoholism and accident. Irene had apparently had to spend all her savings on the fast sleigh home, to be with her dying mother. She’d borrowed from some of the worst tear-jerker family epics she knew, and was quite proud of the result. ‘Of course my cousin’s never been outside Russia in his life, but he knew where I was living . . .’

Several of her listeners sighed in sympathy. In-flight entertainment consisted of looking over the edge or passing round bottles of vodka and slivovitz, and Irene’s story had drawn more attention than she’d really wanted. She pressed her knuckles against her lips. ‘Please forgive me – I’m just so worried about poor Mamma.’

Kai might not have been able to understand the Polish, but he could take a cue. He slipped an arm round her shoulders and held her close. ‘Please forgive my cousin,’ he said in Russian. ‘I think she needs to rest.’

To general nods, Irene let herself relax. It was true that she was exhausted. It had been a long day, and far too full of excitement. Forgotten bruises were making themselves felt, now that there was nothing to do but sit and wait for the flight to end.

‘Get some sleep,’ Kai murmured in her ear. ‘I’ll wake you if . . . well, if anyone attacks.’

Irene quirked a smile. ‘Thank you,’ she whispered and let her head rest on his shoulder, closing her eyes. She tried to clear her mind for sleep, difficult as it was. But Kai was warm against her, even through the thick layers of their clothing, and despite her dislike of heights, next to him she felt safe. He’s a dragon. He’ll catch me if I fall . . .

When she opened her eyes again, the sky was bright and pale and cloudless, and the air was bitterly cold. They joined a queue of incoming aerial traffic diving in towards a huge hexagonal building sheathed in panes of glass and mother-of-pearl. A huge clock on the side, gleaming with brass and surrounded by astronomical symbols, showed that it was six o’clock in the morning.

Irene rubbed her eyes and looked up at Kai. ‘Didn’t you get any sleep?’

‘Enough.’ He didn’t look rumpled or half-asleep, though; he looked keen and sharp, as though the wintry night air had put a new edge on his energy. ‘Look at the city below. You can see all the landmarks.’

Irene gritted her teeth and peered over the edge of the sleigh at St Petersburg below them. ‘It’s . . . big,’ she said, not very helpfully. Her understanding of the city’s geography would have been better if she hadn’t been trying not to think about falling out of the sleigh and landing on said geography.

‘I think that’s the Winter Palace down there.’ Kai pointed at a building on the waterfront, which sparkled gold and blue in the morning light. ‘Lovely architecture.’

It was very efficient of Kai to be scouting out the terrain and spotting buildings that were part of the Hermitage complex. Irene should be complimenting him on his good work, rather than fighting motion sickness and vertigo. ‘How nice,’ she muttered.

Kai gave up on her, and continued leaning over the edge to watch as the sleigh came in to land. The reindeer cantered through one of the archways in the building’s walls and downwards, until they were drawing the sleigh over the ground rather than through air, landing with barely a bump. They touched down inside a huge open hall: it was crowded with other sleighs, shuffling passengers, guards and heavily loaded porters. The sound of hundreds of people shouting at each other was almost physically painful.