He buzzed his secretary. ‘I need to travel to Liège. At once, and in private.’

Near Liège, Belgium

Nick had never thought about monks retiring. If he ever had, he’d have assumed they just carried on until they died, like the pope. He certainly wouldn’t have guessed the reality. Brother Jerome had swapped the Society of Jesus for the drab mortification of the suburbs: a cul-de-sac of brick and pebble-dashed bungalows on the edge of a small town. It felt like the end of the world.

Nick parked the car against a hedge to hide the broken window. Low clouds were holding back the dawn; the world was sunk in shadows, a thousand shades of grey. A woman in a quilted jacket walked a terrier along the opposite pavement; she shot them a suspicious glare as she passed. Otherwise, the street was empty.

Emily led them up a path to a white front door and rang the bell. Nick rubbed his hands together. The cold air was the only thing keeping him awake right now.

Emily rang the bell again. A second later, Nick saw movement behind the blurred glass panels in the door. A voice mumbled at them to be patient while keys jangled and locks clicked. The door cracked open on its chain and a gaunt face peered through the gap.

His eyes widened. ‘Emily. Was I to expect you?’ He noticed Nick. ‘And a friend. Who is he, please?’

If Andy Warhol had ever taken holy orders and retired to Belgium, perhaps this was what he’d have looked like. Brother Jerome was a thin, bony man with a mop of white hair that almost touched his eyes. He wore a Chinese-patterned bathrobe, loosely knotted so that when he walked his bare legs were exposed right up to his thighs. Nick had the unpleasant suspicion he was naked underneath it.

He unchained the door and kissed Emily on both cheeks; she stiffened, but didn’t pull away. Nick got a nod, but Jerome was already leading them into a room off the hall.

Nick looked around in amazement. The room was a mess. Books and papers overflowed from shelves that had been screwed to every available inch of wall. Mould frothed on the half-empty mugs that clustered around the battered easy chair in the middle of the room, which had several more towers of books wobbling uncertainly on the arms.

Jerome headed for the kitchen. ‘You would like some coffee?’

No one else did. Through the door, Nick saw him boiling a kettle.

‘So – Emily. It is a long time, yes? How have you been?’

‘Fine.’

‘I have thought perhaps I never see you again.’

‘We’ve got a book we’d like you to look at.’

Jerome came out of the kitchen with a steaming mug. It looked as though it hadn’t been washed up in weeks.

‘You want to give this to me?’

‘We want you to help us.’

The words had an extraordinary effect on Jerome. His bowed head suddenly snapped up with a furious stare; his body went rigid.

‘Do you know why I am here?’ He flung out an arm at the dilapidated living room. Hot coffee spilled over his fingers and dribbled onto the carpet, but he didn’t notice. ‘Do you know the reason of this exile? Do you?’

Emily bowed her head. A tear ran down her cheek. Nick moved closer to protect her, but neither she nor Jerome noticed. He had no part in their story.

‘I’m sorry,’ Emily whispered. ‘If I could go back…’

‘You would do the same. And so would I.’

As abruptly as it had flared up, his anger died away. He stepped forward and wrapped his arms around Emily. Her face was hidden from Nick, but she looked as though she was hugging a corpse.

Jerome stroked her hair. ‘Let us no longer deceive ourselves with remembrance of our past pleasures. We only spoil our lives and sour the sweets of solitude.’

Emily pulled back – gently – and straightened her hair. ‘I’m sorry to disturb you. But we need your help. And… I thought you would appreciate this.’

‘Let me see.’

At a nod from Emily, Nick pulled the defrosted bestiary out of his bag. Jerome licked his lips and held out his hands. ‘Please.’

Nick gave him the book. Jerome almost snatched it from him. He lifted it up like a priest reading the gospel and examined it.

‘The binding is of the seventeenth century.’ He turned it in his hands. ‘Calfskin leather with blind stamping, possibly German workmanship.’

‘I thought it was supposed to be fifteenth century,’ Nick interrupted. Brother Jerome fixed him with a scornful look.

‘It has been replaced. Bindings wear out faster than pages. As bodies fail before the soul.’

He carried the book to a wooden bureau in an adjoining room and sat down. From a drawer, he extracted a foam cushion and a pair of thin gloves. He pulled them on over his bony fingers, a pathologist preparing for an autopsy, and laid the book on the desk. He slipped a finger under the cover and gently tugged, peeling it away from the page beneath to rest open on the cushion.

The illuminated lion stared off the page. Nick glanced at Jerome to see if he recognised it, and caught the old man giving him a sly glance from under his white fringe. Neither said what the other was thinking.

Jerome thumbed the crease of the page. ‘This book has not been well preserved.’

‘It was in a library that got flooded.’

‘Beyond the obvious. There is a gutter here.’

Nick stared, not sure what he was looking for. ‘What’s a gutter?’

‘The bones of a missing page.’ Jerome pushed the cover and the first page further apart. Nick saw the edge of a thin strip of parchment, barely protruding from the spine.

‘A page has been cut out.’

‘Is that normal?’

‘Depressingly so. It is hard to steal a book but very easy to take a page. An individual leaf can fetch thousands of dollars. All these ancient manuscripts are worth far more in pieces than as a whole.’

‘It’s been going on for centuries,’ Emily added. ‘This one is not so long ago.’ Jerome pointed to a series of dark smudgings on the topmost page. ‘You see here the marks where the missing page has soaked through. It has only been taken after the flood.’

Emily and Nick looked at each other, daring each other to state the obvious. Jerome watched with a wicked smile, enjoying their discomfort.

‘Gillian was a professional who loved books,’ said Nick at last. ‘She’d never have mutilated it like this. She worked in museums, for God’s sake.’

Emily avoided his gaze. ‘It would be nice to know what was on that first page,’ was all she said.

‘Maybe we find more.’

Jerome fumbled in a drawer of the desk and brought out a thin metal tube that looked like a pen. He twisted the end, and a pale beam of purplish light glowed from the tip.

‘Ultraviolet,’ he said. He shone it on the inside of the cover. To Nick’s amazement, dark letters appeared on the stiff board, emerging under the light like hidden runes. Unlike the dense bestiary text, this was written in a thin, spidery hand.

‘How did that get there?’ Nick’s voice was barely a whisper. ‘It was written by the book’s owner. When somebody else got it – by gift or purchase, or perhaps by stealing – he erased the mark of the first ownership. But the trace remains still.’

‘What does it say?’

Still holding the light, Jerome picked up a magnifying glass to read it more closely.

‘“Cest livre est a moy, Armand Comte de Lorraine.” ’

‘What does that mean?’

‘It means it belonged to the Count of Lorraine. Once. The Count of Lorraine possessed one of the greatest libraries of early modernity.’

Nick didn’t know what Jerome meant by ‘modernity’, but guessed it didn’t fit with anything he thought of as modern.

‘What happened to it?’

Jerome shrugged. ‘It was lost. The Count’s heirs sold his collection piece by piece, or allowed unscrupulous men to loot it. What was left, I think, passed to the city archives of Strasbourg in the nineteenth century.’

Page by page, Jerome’s gloved fingers worked their way through the bestiary until he reached the end of the book. There was no illustration on the last page, only a couple of lines of text and a rectangular brown stain on the parchment about the size of a postcard. Nick swallowed hard and fought back the urge to pull out the playing card to overlay it. It looked as if it would fit perfectly.