‘He doesn’t make me feel like I’m dying inside,’ Hélène burst out. She mopped her eyes. ‘I only want a normal life.’

He reached out and took her hands. ‘What if I gave it up? If I was just an ordinary guy…I’ll hand in my notice, get a job doing something else.’

‘Doing what?’

He paused, realizing that he couldn’t think of a single thing in the world that he could be doing instead of police work. ‘I don’t know,’ he conceded.

She shook her head, and snatched her hands away from his. ‘You were born to be a cop, Luc. You’d hate anything else. And you’d hate me, for making you leave the thing you love most.’

He was silent for a few moments, thinking. He knew, deep down, that what she was saying was true. He’d neglected her, and now he was paying for it. ‘Then what if I just took some time off, say a month? We could go away somewhere together-wherever you like, how about Vienna? You always talked about going to Vienna. What do you think? You know, the opera, take a ride on a gondola, all that stuff.’

‘Gondolas are Venice,’ she said dryly.

‘Then we’ll go to Venice as well.’

‘I think we’re a little past that, Luc. Even if I said yes, then what? After a month it would all start up again, same as before.’

‘Can you give me a chance?’ he asked quietly. ‘I’ll try to change. I know I have the strength to change.’

‘It’s too late,’ she sobbed, looking down into her glass. ‘I’m not coming home with you tonight, Luc.’

The place wasn’t quite what Ben had expected to find. To him, the term ‘laboratory’ conjured up images of a modern, spacious, purpose-built and fully equipped facility. His surprise had mounted as he followed the directions the guy on the phone had given him and arrived at the old apartment building in central Paris. There was no lift, and the winding staircase with its tatty wrought-iron banister rail carried him up three creaking floors to a narrow landing with a door on either side. He could smell the musty, ammonia smell of damp.

As he climbed the stairs, he kept thinking about the incident at Notre Dame. It haunted him. He’d been cautious on the way here, stopping frequently, looking in shop windows, taking note of people around him. If there was a tail on him now, he couldn’t spot it.

He checked the apartment number and rang the buzzer. After a few moments a thin young man with curly dark hair and a sallow complexion opened the door and showed him into what turned out to be just a pokey little flat.

He knocked at the door marked LAB, paused a beat and went inside.

The lab was no more than a converted bedroom. Work surfaces sagged under the weight of at least a dozen computers. Piles of books and folders everywhere threatened to tip over. At one end was a sink unit and an array of battered scientific equipment, test tubes on a rack, a microscope. There was barely space for the desk, at which sat a young woman in her early thirties, wearing a white labcoat. Her dark red hair was tied up in a bun, giving her an air of seriousness. She was attractive enough to wear no makeup, and her only adornment was a pair of simple pearl earrings.

She looked up and smiled as Ben came in.

‘Excuse me. I’m looking for Dr Ryder?’ he said in French.

‘You found her,’ she answered in English. Her accent was American. She stood up. ‘Please, call me Roberta.’ They shook hands.

She watched him for a reaction, waiting for the inevitable raised eyebrow and mock-surprise ‘oh-a woman!’ or ‘my, scientists are becoming prettier these days’ kind of comment that virtually every man she met came out with, to her great annoyance. It had almost become her standard test for gauging men she met. It was just the same infuriating knee-jerk response she got when she told guys about her black belt in Shotokan karate: ‘oh, I’d better watch my step’. Assholes.

But as she invited Ben to sit down, she didn’t notice a flicker of anything cross his face. Interesting. He wasn’t the typical sort of Englishman she’d come to know-no pink jowls, beer belly, awful taste in clothes or combed-over bald patch here. The man opposite her was tallish, something under six feet, with an easy grace in jeans and a light jacket over a black polo-neck that hung on a slender but muscular frame. He was maybe five, six years older than she was. He had the deep tan of someone who’d been spending time in a hot country, and his thick blond hair was bleached by the sun. He was the kind of man she could go for. But there was a hardness in the set of his jaw, and something in those blue eyes that was cold and detached.

‘Thanks for agreeing to see me,’ he said.

‘My assistant Michel said you were from the Sunday Times’

‘That’s right. I’m working on a feature for our magazine supplement.’

‘Uh-huh? And how can I help you, Mr Hope?’

‘Ben.’

‘OK, what can I do for you, Ben? Oh, by the way, this is Michel Zardi, my friend and helper.’ She waved a hand at Michel, who had come into the lab to look for a file. ‘Listen, I was just going to make a coffee,’ she said. ‘Want one?’

‘Coffee would be good,’ Ben said. ‘Black, no sugar. I need to make a quick call. Do you mind?’

‘Sure, go right ahead,’ she said. She turned to Michel. ‘You want a coffee?’ she asked him. Her French was perfect.

‘Non, merci. I’m going out in a minute to get some fish for Lutin.’

She laughed. ‘That damn cat of yours eats better than I do.’

Michel grinned and left the room. Roberta made the coffee while Ben took out his phone. He called the number for Loriot, the book publisher Rose had mentioned. No reply. Ben left him a message and his number.

‘Your French is pretty good for an English journalist,’ she said.

‘I’ve travelled around. Yours is pretty good too. How long have you lived here?’

‘Nearly six years now.’ She sipped the hot coffee. ‘So let’s get down to business, Ben. You want to talk to me about alchemy? How did you hear about me?’

‘Professor Jon Rose at Oxford University put me on to you. He’d heard about your work and thought you might be able to help me. Naturally,’ he lied, ‘you’ll be fully credited for any information used in the article.’

‘You can leave my name out of it.’ She laughed grimly. ‘Probably best not to mention me at all. I’m officially the untouchable of the scientific world these days. But if I can help you, I will. What d’you want to know?’

He leaned forward in his seat. ‘I’m looking to find out more about the work of alchemists such as…Fulcanelli, for instance,’ he said, sounding deliberately casual. ‘Who they were, what they did, what they might have discovered, that kind of thing.’

‘Right. Fulcanelli.’ She paused, looking at him levelly. ‘How much do you know about alchemy, Ben?’

‘Very little,’ he said truthfully.

She nodded. ‘OK. Well, first off, let me get one thing straight. Alchemy is not just about turning base metals into gold, all right?’

‘You mind if I take notes here?’ He drew a small notepad from his pocket.

‘Go ahead. I mean, in theory it’s not impossible to create gold. The difference between one chemical element and another is only a question of manipulating tiny energy particles. Strip off an electron here, add one on there, and you can theoretically change any molecule into any other. But for me, that’s not what alchemy is really about. I see the base metals into gold thing as more of a metaphor.’

‘A metaphor for what?’

‘You think about it, Ben. Gold is the most stable and incorruptible metal. It never corrodes, never tarnishes. Objects of pure gold stay perfect for thousands of years. Compare that to something like iron, which rusts away to nothing in no time. Now, imagine if you could find a technology that could stabilize corruptible matter, prevent deterioration?’