He slid off the stone and paced around me. ‘If every challenge was overcome at the first attempt, it would never have been a challenge. Do you know how many sheets of paper and copper I ruined to make the playing cards? How many three-legged bears and unicorns that looked like goats?’

‘Your unicorn still looks like a goat.’ I wanted to wound him, but he shrugged it off with rare modesty.

‘Catch me one and I will draw it better.’

‘At least a unicorn would be worth something.’

‘But we are hunting a rarer beast. If – when – we make it right, a more valuable beast.’

He pulled a coin out of his pocket and flipped it towards me. He must have brought it with him precisely for this piece of theatre, for I never otherwise knew him to carry any money. I snatched it out of the air.

‘Imagine that is your bride.’

The image on the coin was a man, John the Baptist, his head framed in a heart-shaped halo. I read the inscription around the border. IOHANNIS ARCHIEPISCOPVS MAGVNTINVS. John, Archbishop of Mainz.

‘I saw Dunne the goldsmith yesterday,’ Drach said. ‘He has been carving a new plate which he says will make the lettering more even. But it takes hours to make. He cannot afford the time without extra payment.’

I was not listening. The lettering on the coin had transported me back to my childhood. Some colleagues of my father from the mint had lived in our house for a time. A die maker had been one. I remembered tiptoeing into his room one afternoon and watching him at work. He took the block of iron that he had engraved with the design, held a steel rod against it and struck it hard with a hammer. Sparks flew; I whimpered in surprise. He heard me and beckoned me over. He let me hold the steel rod and told me it was called a punch. He showed me the end, which had been carved away so that the letter A stood proud on its tip. When he struck it against the die, it left a perfect imprint in the iron. Later it would be filled with gold, and the impression of that letter hammered into the coin. Such was the unceasing cycle of creation and reproduction: punch and form, male and female, stroke and imprint.

Like all obvious ideas, the wonder afterwards is that it took so long to discover. Why had we wasted months trying to carve the words with a graving tool, when Dunne and I both knew that the best way to imprint letters in metal is with a punch-stamp? All I can say is that Drach had engraved his cards, and we were so bent on following his method we did not pause to think.

Drach was watching me impatiently. He hated to be ignored. I met his gaze and smiled. Of course I saw what he was doing. But I could not help myself.

‘How much is Ennelin’s dowry?’

Paris

‘Could they have followed me?’

It had taken Emily three hours to get back. She’d changed trains, jumped indiscriminately on and off buses, browsed in the reflections of shop windows, made sudden detours – all the while looking over her shoulder for any sign of pursuit. Darkness had fallen by the time she sneaked back into the hotel. She’d shaken Nick awake from his jet-lagged sleep and dragged him to a café in a quiet backstreet near Montparnasse. She still didn’t feel safe.

‘If they’d followed you, they’d have come back to the hotel.’ Nick sipped his beer and looked around the café for the dozenth time. He couldn’t sit still. ‘It was lucky you had that pepper spray.’

‘I had a bad experience once.’ Emily barely moved. Shock gripped her like stone. ‘It must have been the book. It must have triggered some kind of alarm somewhere. A tripwire.’

Not so long ago it would have sounded ludicrously paranoid. Now, Nick just nodded. ‘Maybe that’s how they found Gillian. That’s why she left her library card in the bank vault.’ The cards Gillian had left them were beginning to look more like a box of sharpened knives than a treasure trove. ‘If only we could find her that easily.’

Emily cupped her palms around her mug of coffee in silence. Twice she looked as if she was going to say something, but held back. Nick could guess what it was.

‘If you want to go home, I understand.’ He said it quickly, knowing he’d regret it if he gave himself time to think about it. ‘God knows what those guys would have done to you if you hadn’t escaped. There’s no reason for you to risk it for Gillian.’

Emily seemed to flinch. ‘I’m not…’ She trailed off, paused, began again. ‘I’m not going home.’

He knew he ought to argue but he didn’t have the will. She flicked him a tentative look and he held it, trying to reassure her. It was hard when he had so little to give.

‘At least I got something for my troubles.’ Warmth returned to Emily’s face. ‘Gillian was reading up on a physiologus – a book of beasts. I’ll bet that was the book she found the card in. There must have been one in the chateau’s library.’

Nick thought about it for a second.

‘I know the man who’d know.’

‘Atheldene.’

The familiar voice, so intimidating in its studied neutrality. ‘It’s Nick.’

A taxi drove past the phone box. The noise of its wheels on the slick cobbled street drowned out Atheldene’s surprised silence. As it died away, Nick heard, ‘Any news of our mutual friend?’

‘Maybe – we’re not sure. We need to check the list of books she recovered from the chateau. Can you do that?’

‘Perhaps with a good enough reason.’

‘Gillian’s missing. Emily went to the Bibliothèque Nationale today and almost ended up the same way. How’s that for a reason?’

‘I’m very sorry to hear it.’

Nick glanced at Emily, watching through the phone-box door. She nodded.

‘Gillian found a card. An old one.’

‘The Master of the Playing Cards, I presume.’ Atheldene didn’t sound surprised. ‘Have you got it?’

‘We think she may have found it in some sort of bestiary, or…’ Nick stumbled over the word. ‘Physiologus.’

‘Really?’

Nick could almost imagine the raised eyebrow, the searching stare. He was glad of the phone line between them. He waited out the silence.

‘I’ll check the inventory from Rambouillet. Can I call you back on this number?’

‘It’s a payphone.’

‘I’ll be quick.’

Atheldene hung up. Nick waited in the phone box, scanning the road through the cracked glass. A little way down the street, a homeless man sat hunched under a filthy quilt on a raft of cardboard boxes. Nick was amazed he hadn’t already frozen. His hand dipped to his pocket to find some euros, but fear restrained him. What if the old man wasn’t what he seemed? He was sure he’d read books where spies dressed as bums to conduct surveillance. Was the man looking at him? Nick watched him carefully and kept his hand in his pocket.

A shadow crossed his line of sight. He jumped, but it was only Emily. She walked across the empty street and crouched beside the homeless man. She dropped some coins into his styrofoam cup and exchanged a few words, then hurried back. Nick felt ashamed.

‘What did he say?’

‘He said you should stop staring at him.’

Before Nick could feel even more guilty, the phone rang. He seized the receiver gratefully.

‘Yes?’

‘Good news. There was a bestiary in the old man’s collection. Just the one. Gillian catalogued it. Date, mid to late fifteenth century. Remarks: some stylistic similarities with the workshop of the Bedford Hours Master.’

‘The who?’

‘I’ll tell you later. You’ll like it.’

‘When can we see the book?’

A dry laugh. ‘I’m afraid it’s not quite so straightforward.’

‘What do you mean?’

‘Well for one thing, the book’s not in Paris any more. Remember it had been soaked through? The conservators took it away to their controlled storage facility.’

‘Where’s that?’

‘Brussels.’

Nick swore. ‘Can we get in there?’

‘I could get you in there.’ There was an implicit offer in the sentence, a stress that opened a negotiation. Nick’s mind raced. He looked down the street and saw that the beggar had gone. Had he used Emily’s gift to find a warm bed for the night – or was he even now telling a man with a broken nose where to find Nick and Emily?