Sarah leaned forward on the daybed. In the gloomy afternoon light, her eyes glistened brightly, and her diamond choker sparked off curved rainbows and winking stars. Collis could smell her perfume, and he knew that he’d forgotten how beautiful she was, and how sensual.

‘I didn’t really want to involve you in this at all,’ Collis said. ‘More than anything, I didn’t want to take advantage of your friendship. But there are other considerations, far more pressing. I’m afraid you were perfect for what I wanted to do.’

‘But what did you want to do?’ she asked him. ‘You still haven’t told me.’

Collis stood up and paced across to the spyhole. He lifted the flap, and a dusty ray of sunlight pierced the room. The rain must be clearing outside, he thought. He wished to God he’d never been headstrong enough to believe that his preposterous plan would work.

‘Your father and I, when it comes to business, are mortal enemies,’ he said. ‘For me to make my fortune, I desperately need to build my railroad. For him to preserve his fortune, he desperately requires that I shouldn’t. So we’re at total odds; and there is no way the conflict can be resolved unless one of us resorts to unfair pressure.’

He turned to her, with a resigned smile. ‘That’s why you’re here. You’re my unfair pressure. I was going to have you drugged with tincture of opium; then undressed, with Maria-Mamuska as a chaperone, and photographed by Mr Figgis. I was then going to have a sample calotype sent to your father, with a threat for money. Signed anonymously, of course, by the Calotype Gang, or whatever came into my mind.’

Sarah looked back at him with an expression of disbelief. ‘He wouldn’t have paid,’ she said. ‘He would have turned San Francisco upside down, looking for the culprits, with the express intention of having them hanged.’

‘Precisely,’ said Collis. ‘Except he never would have found them.’

‘No,’ she said. ‘I don’t suppose he would. Even I don’t know where we are.’

Collis sat down again, breathing out smoke. ‘We would have sent a second calotype, maybe even a third, with more demands. Your father would have gone berserk with rage. Then, at the right moment, I would have approached him at his office, very discreetly, and told him I had been given to understand that he was being put under pressure from blackmailers. He would have been angry with me at first, and even suspected I had something to do with it. But my alibis would have been seamless, and after a while he would have had to listen. I would have offered to act as a middleman — to retrieve the calotype negatives, all of them, provided he did me a favour in return. I wouldn’t have asked for much. Just that he should withdraw from all active resistance to the Sierra Pacific Railroad, and announce in the Evening Bulletin that he considered the railroad inevitable, desirable, and profitable to all who might care to invest in it.’