It was an idea that required some chunky mathematics – maths that turned out to be as useful for piecing together real documents as detecting fakes. Nick had emailed him afterwards to compare notes, and from there they’d become occasional collaborators. Randall had also brought him into Gothic Lair. For several months they’d roamed across the online fantasy kingdom almost every night: killing dragons, saving princesses and storming castles filled with unimaginable treasures. Before Nick swapped the company of the princesses for Gillian.

A nimbus of white light flared around Urthred the Necromancer as he came alive again.

‘Any joy?’

‘All I got was garbage.’

Nick had spent enough frustrated hours waiting for a computer to deliver its verdict to know not to expect much. But this wasn’t just another exercise. He squeezed the mouse in frustration, accidentally sending the Wanderer scuttling across to the far corner of Urthred’s chamber.

‘It’s not the algorithm. The picture’s completely screwed up.’

‘What do you mean?’ Nick guided the Wanderer back to the centre of the room. ‘Is the file corrupted?’

‘It’s not the file.’

Belatedly, Nick realised Randall was trying to tell him something.

‘You know my analogy about the ripples in the pond? Well, imagine you pull up a sample and it turns out the pond’s not even water. That’s what I’m talking about.’

‘I don’t-’

‘Someone’s done something to this file. The picture’s still there, obviously – I can see it fine. But something’s going on under the surface that’s completely changed the file coding.’

Nick finally got it. ‘Encryption.’

‘Exactly. Someone’s buried something inside this file that doesn’t show up when you look at the picture. There are over five million individual pixels in that image, each one stored as a string of six characters. All you have to do is change a handful of them so that those numbers and letters spell out a message, and you can hide a whole string of text without anyone knowing. Invisible to the naked eye.’

Nick knew how it worked – he’d come across it before. Why didn’t I think of that?

‘Would Gillian have known how to do that?’

‘Sure. There are a bunch of programs you can get to do it for you. Figure out which one she used, run the file through and it’ll just pull the data back out. It’s probably password-protected though.’

Bear is the key. ‘I’ll get right on to it.’ For the first time since Gillian’s name had lit up on the screen, Nick felt hopeful again.

‘You could try to her IP address as well,’ Randall suggested. ‘See where she got to?’

‘She Buzzed me. Peer to peer. I thought that was impossible to trace.’

‘Someone must have managed it.’ Urthred turned and looked at him. ‘Otherwise how did they find you?’

On screen, Nicholas the Wanderer leaned on his staff and stared across the moonlit chamber at the Necromancer. In a busy Internet café on lower Broadway, Nick leaned back on the stainless-steel barstool. The place was full: no dwarves or magicians, but just about everyone else. Filipinos and Indians checking in with their families back home; European backpacker-types bragging to their blogs; some Mexican kids playing Counterstrike. A tiny, infinitesimal fraction of the chatter shooting around the world over wires and airwaves. Yet through all that hubbub, someone had traced a message from a frightened girl in Europe to an apartment in New York. Nick glanced over his shoulder. A Korean man with pimpled cheeks and a buzz cut seemed to be waiting for a free machine. Was he familiar? Had he seen him before?

‘Are you at home now?’ Randall asked through the earphones.

Nick shook his head, then remembered Randall couldn’t see. ‘Home’s a crime scene. I’m not allowed back there.’

‘That’s probably a good thing.’ Urthred came around the table to stand right in front of the Wanderer. ‘You’ve got to be careful. You and I, what we do, we’re so used to seeing this illegal shit as paper, pictures, numbers we hack up. But this is real. Real people, real bullets. Don’t fuck around.’

‘I’ll be careful.’

Nick hit ESCAPE and dropped out of Gothic Lair. Into a world where there were more than monsters to fear.

XVIII

Paris, 1433

Aeneas once said that a man’s life is a blank page on which God writes what He will. But paper must be formed before it can take the ink. I considered this while I waited in the paper maker’s workshop. The whole room stank of damp and rot, like an apple store at the end of winter. A woman sat at a table with a knife and a pile of sodden rags, cutting them into tiny scraps. These went into a wooden vat, where two apprentices with long paddles beat them into a porridge. When this was ready it would be pushed to the side of the room to fester for a week, then beaten again and again until the original rags were utterly obliterated. Only then would the master paper maker scoop out the paste in a wire form, squeeze it dry in his press, harden it with glue and rub it with pumice to make it smooth beneath the pen. So must a man’s life be dissolved and remade before one drop of God’s purpose can be written on it.

The paper maker brought me a bale of paper bound with string. Behind him, one of the apprentices turned the screw on the press. There was a slurping sound as water oozed out of the wet paper into the interleaved layers of felt. In a moment of whimsy I imagined the water as ink, as if words themselves could be squeezed out of the paper, destiny unwritten.

‘Your master must keep you busy.’ The paper maker took the coins I gave him.

I shrugged. ‘We sell salvation to sinners and knowledge to the ignorant. We never want for customers.’

I carried the paper back to our workshop, across the bridge so thick with houses you never saw the river. The only sign of water was the grumble of the milling wheels in the arches below. I passed under the watchful gazes of the twenty-four kings of Israel carved into the face of Notre-Dame cathedral, and crossed the invisible river again into the warren of streets around the church of St Severin, in the shadow of the university. This was my home. Goose down and parchment shavings drifted in the air like snow; even to breathe was to take in great lungfuls of them. Copyists sat by open doors and windows with books propped open on stands beside them; illuminators called new and fabulous beasts into being in the capitals and margins of their manuscripts, and students in threadbare finery haggled with the stationers, trying to save their coins for the whores across the rue St Jacques.

The shop was about halfway down a lane, with a cloth awning and a few battered books laid out on a table in front. A large poster nailed next to the door advertised the stationer’s many hands: heavy blackletter with ornate initials; fine cursives whose stems twined like a tangled garden; thickset minuscules that only a glass could read. On the corner of the house, the figure of Minerva sat atop a pile of books and peered down at the street.

‘There you are.’

Olivier de Narbonne – stationer, bookbinder, my employer – looked up from the Bible he had been poring over with a customer. I was about to sidle upstairs to begin work on a piece I had promised him that day, but he beckoned me over, steering his customer so that he could introduce us.

‘A countryman of yours. Allow me to present Johann Fust. From Mainz.’

I knew where he came from. I knew where he had lived, where he had attended church and where he had gone to school. I knew he was two years older than me, though with grey already flecking his dark hair it looked more. I had fled the length of Christendom to escape my past, each calamity toppling into the next like dominoes. Yet here in Paris a face from my childhood stood in my shop, smiling curiously.