Sharkskin men and women writhed and danced in tanks of brine, their grey limbs sliding fluidly behind the curved glass walls, their hair like green pennants. A million customers might pass through Losoto’s underground market, plucking at the banks of treasure, and yet the stock never diminished. It could not be eroded. Every artefact in the empire found its way here eventually, to lie in wait for a spark of desire.

Ida clutched her book as fiercely as a mother holds a long-lost child. ‘Goodman was an Unmer Lord?’ she asked the shopkeeper.

‘Lord, libertine and a formidable sorcerer to boot. He lived in a house up there, less than a hundred yards from here.’ He jabbed a finger up at the vaulted brick ceiling, beyond which the streets of Losoto would be basking in the sunshine.

‘Then this book is magical?’

The shopkeeper smiled broadly, displaying the diamonds set in his teeth. ‘Who can say? The Unmer invested so many of their creations with magic. You must read it all to discover its value. Passion, sexual ecstasy, horror and peril. Anything is possible between the covers of such a book.’

She nodded urgently.

‘But there’s more,’ he added. ‘Now that you possess a map of seduction, you must acquire a compass and a sextant, so to speak, to facilitate your success.’ He steered her towards a dark cabinet stuffed with bulbous phials that gleamed like squid. ‘These Unmer potions have been dredged from the beds of sixteen seas. Look here.’ He picked up a green bottle. ‘Drink this to cleanse and revitalize your mind; it tastes like spring rain. And this -’ He chose a tiny, empty jar ‘- is a singularly precious ointment.’

‘What is it?’

‘Clarity.’

‘How much do they cost? I don’t know-’

‘And here is stamina.’ This bottle was sunflower-yellow, the next one pink. He scooped them into his arms like glazed fruit sweets. ‘And lucid dreams and lightness of step – ah, here is an enigma. This tincture allows one to see colours hidden in other people’s shadows and thus perceive hidden intentions. These three are the bottled auras of young boys sacrificed at Unmer altars; their ghosts will be lingering nearby. How long do you plan to stay?’