And a secret panel at the back of the office, opened by a catch worked by one of the madam’s polished fingernails, revealed another room, lit by a single gas lamp, entirely enclosed. The madam allowed the three of them inside, then backed out gracefully, closing the door behind them.

Luis glanced around. After the brilliance of the day the gaslight seemed dim indeed. There were no other doors, no windows, no furniture. But he could guess why they were here. This entirely sealed-up room was a gateway to the widdershins world, a place through which Waltzers could pass without fear of observers.

Hackett grinned at them both. ‘Leave your bags here; you’ll not be needing them where we’re going. I just want to make sure our precious cargo is safe, for we leave tonight, with our friends, on the River Goddess bound upstream for Memphis. All set? If you need a puking pill I’ve got some to spare. Widdershins we go. One, two, three—’

The site of this parallel New Orleans struck Luis as not much different from the regular version – given the absence of all the works of mankind, of course – and he wondered how dissimilar the details were of the braiding of the great river as it poured sluggishly across this flat, marshy landscape. But Luis’s feet were dry, more or less; the slight rise on which the bawdy house stood evidently persisted here, a scrap of ground marginally higher and drier than the rest.

Still, they were all sweating immediately.

And Hackett slapped his neck. ‘Got you, you swine! Further north of here, you know, there are all sorts of exotic beasts to be seen – and to run from. Giant camels, horses the size of big dogs, cave bears, lions: critters from which modern Americans have evidently been spared acquaintance by the veil of extinction. But here, nothing but mosquitoes, and they seem to persist everywhere. Oh, and alligators; don’t go near the water.’ He pointed west. ‘There are our passengers.’

Luis saw what appeared to be an old army field tent, battered, roomy, its heavy canvas held in place with ropes and pitons driven into the soggy ground. A small fire smoked near an open doorflap, and shirts and trousers and greyed underwear were laid out on the spine of the tent, drying out after a washing.

And in the shade of a kind of porch, under a spread-out mosquito net, two men were sitting. They were both black. As the three Englishmen approached, one of them whipped aside the mosquito net, stood, and faced them armed with a kind of improvised club. The other, evidently older, stayed sitting, his back against a heap of blankets.

Hackett spread his hands. ‘It’s only me, Simon. Oswald Hackett at your service. Well, who else would it be? And these two fine fellows are here to help you make your journey north, beginning tonight.’

The younger man lowered the club and smiled. ‘Mr Hackett. So good to see you again.’

Luis was surprised at the man’s accent: well spoken, even refined, at least given Luis’s limited experience of American intonation. But this man, Simon, had evidently been used brutally; one cheek bore an ugly-looking scar, badly stitched, and the opposite eye was closed by swollen flesh.

The older man, meanwhile, his hair and ragged beard streaked with grey, barely stirred.

There was a round of introductions. It turned out that Simon and the other man were grandson and grandfather respectively.

Hackett bent to speak to the old fellow, doffing his hat. ‘And you, Abel. Do you remember me? I carried you over from New Orleans.’

‘F’om tha’ cat house,’ Abel said. ‘Haw haw! Shoulda lef’ me there and the gels wudda finish’ me off.’

‘Then I came back with Simon … You remember?’

‘Sho I ’member, Massa Hackett.’

‘Please don’t call me massa.’

‘No, massa.’

‘Come,’ Simon said. ‘Sit in the shade with us. We have root beer and I can brew a coffee …’

It was a strange gathering that they made in the shade of that antiquated tent, Luis thought, three Englishmen and two runaway slaves, drinking root beer and eating hard-tack biscuits – five men all alone in this widdershins world, he supposed, save for the cave bears and the dog-sized horses (which he wasn’t entirely sure he believed in), and any other Waltzer who might be popping back and forth for his or her own purposes.

Hackett was quick to reassure the men that the plan he had made for their escape was still in place. ‘We steam upstream as far as Memphis on the Goddess, and then change. At Cairo we change again and steam up the Ohio to Evansville, Louisville, Portsmouth. Then it’s overland to Pittsburgh—’

Simon smiled. ‘And across Mason and Dixon’s Line to the free states.’

‘And you’re home and dry,’ Hackett said.

‘If all goes well.’

‘Much can go wrong,’ Hackett conceded. ‘I wouldn’t hide that from you. On the steamer you’ll be huddled close to the boiler; it will be warm enough for you, and you’ll be pitched about in the dark. And you may know that the slave-catchers nowadays have a way of smoking out the holds of boats like this, to be sure there are no stowaways. We have gear for you agin that threat – oilskin hoods, and wet towels for your mouths. But to ride a steamer is still better than walking all the way to the free states through this widdershins world, which is the only alternative. And we three will be with you all the way; we can always Waltz you out of trouble, wherever we are.’

Simon said, ‘I could work in the open if you like. Pose as your servant. I can play the poor ignorant, like Grandfather. Roll my eyes and blubber for Jesus’s mercy.’

‘I’ve no doubt you can, and most convincingly. But you’re runaways, Simon. And everyone knows how the Rail Road works; they’ll be looking out for you all the way up the river. Why, given the Fugitive Slave Law the slave-catchers have the power to cross the Line itself, and the law says they’re not to be impeded in their filthy work, even in free state territory. They even work in cities like Boston and Philadelphia, I’m told.’

‘True, is true,’ murmured the old man. ‘Tha’s why I’m a’goin’ all’a way to Canada. Queen Victoria’s Promised Land. Follow th’ drinking gourd to th’ North Star.’

Hackett nodded. ‘That’s it.’ He glanced at Luis. ‘The “drinking gourd” is the Big Dipper, which points to the pole star.’

‘I’m a’goin’ to shake the paw of th’ British Lion, yes suh.’

‘Yes, you are. But until we’re home free you just stay out of sight as much as you can.’

Luis thought Simon, meanwhile, looked as nervous at the whole prospect as he might have been himself had their roles been reversed – as he had a right to be, of course.

Burdon said, ‘Forgive me for saying this, Simon. You aren’t quite—’

‘What you expected?’ Simon grinned easily, but showed cracked teeth. ‘My background is somewhat unusual. Whether you judge that my subsequent experiences have been the worse for me because of that is up to you …’ He sipped his coffee. ‘As a little boy I was clever and good-looking – that’s not bragging, consider it a fair description of the merchandise. I was befriended by the younger son of the master of the house – this was a cotton plantation in the wilds of Louisiana, with a hundred or so head of slaves – when you’re children, you see, even such categories as slave and master blur into insignificance compared with the vividness of the game of the day. I was four years old.

‘Well, when Alexander – the young master – began his schooling, he was something of a restless soul, and his father, observing I was bright and a calming influence on him, brought me into the house as a companion. Even by then I was aping the masters’ speech, you see, and they would probably say “aping” is an appropriate term. But they dressed me up and encouraged me to speak well and mind my manners, and I became a study companion for Alexander – only at home, of course, never at school or beyond the bounds of the house. And in the process, naturally, I learned a good deal myself. I was brighter than Alexander but not markedly so; of course I knew not to outshine him overmuch in our shared work, but to let him think he could beat me at it – as often, indeed, he could. I was a happy child, sirs, unaware of my unholy indenture. It shames me to say that I was even unperturbed when my mother and my little brothers and sisters were sold on by the master – though later I would be enraged to learn from the other slaves that it was because my mother had refused the master’s lustful designs.