He turned on the flashlight.

He was sitting in a stream that flowed through the bottom of a narrow cave, just wide enough for him to stretch his arms between the walls. Stalactites dripped from the ceiling like candle wax, leaving milky deposits in the water, which disappeared into a cracked pipe beneath the rubble.

‘Nick?’

Emily’s voice cut through the darkness, above and behind him. He swung the beam around to see her disembodied face peering out from the hole.

‘Be careful coming down,’ he warned.

She slithered down the slope head first. Nick caught her and helped her to her feet. If they stooped, the cave was just high enough for them to stand. On the back wall of the chamber he could see a carved image of the Virgin Mary cradling her infant son. The work was coarse, except for a smooth spot above the baby’s head. It reflected the flashlight like a halo.

‘That would have been from the pilgrims,’ said Emily. ‘There must have been some tradition in the Middle Ages that if you touched it you’d be healed, or have your prayers answered, or be lucky.’

Below the statue was a stone basin, a shallow pool. The stream spilled out over its edge, but something gleaming in the bottom caught Nick’s eye. He knelt beside it and reached into the icy water. His hand came out clutching a flat silver quarter.

‘It was one of Gillian’s things – she always threw quarters in wishing wells.’

‘Then where did she go?’

‘Well, we know where the castle is.’

Nick shone the flashlight at the ceiling. Even though he knew what he was looking for, it took him a while to see among the forest of stalactites and the shadows they cast. But at the edge of the cave he found a dark spot that wasn’t a shadow. A hole in the ceiling, a shaft rising towards the castle. On the wall he saw shallow ridges carved into the rock like a ladder.

Emily touched his arm. ‘Are you sure?’

‘Whatever they did to Gillian, they did it in the hotel. I saw it on the webcam, remember? If she got into the castle, she must have got out again.’

‘What if they found out how she did it?’

‘Then they’d have blocked up the hole.’ Don’t let yourself think or you’ll give up. ‘The snow must have covered it over before they could find it.’

He slung his backpack over his shoulder and started to climb.

The walls were slippery, coated in a powdery slime that rubbed off on his fingers, but the shaft was so narrow that he could brace himself against it. With the stone rungs to cling on to, he climbed quickly, flitting in and out of the beam of light Emily shone up. He tried not to look down.

By the time he reached the top the flashlight beam was a faint presence far below. He didn’t even know he’d arrived until he reached up for the next rung and felt smooth stone blocking the way. He paused, resting his weight against the wall. Yet another dead end. But the adrenalin was flowing: he knew Gillian had come this way. He put his shoulder against the stone and heaved.

It lifted free with less effort than he’d expected. Braced against the wall of the shaft, he almost lost his grip. He stiffened and steadied himself. Then he slid the stone aside, opening a narrow gap just wide enough to squeeze into. He hauled himself through and looked around.

He was in the castle. He’d come out into a small round chamber that must be the base of one of the turrets. A staircase spiralled up into the darkness. He craned his head back, looking for the telltale winking light of a security camera or an alarm. Nothing.

Emily clambered through the hole. She clutched his arm as she surveyed the high room, covering the flashlight with her fingers.

‘Do you think anyone heard us?’

‘Let’s hope not.’

They tiptoed up the stairs. On the first landing, a door led through into a long low-vaulted corridor. Recessed lights, hidden behind the arches, cast yellow pools of light on the flagstones.

Emily shivered. ‘It looks like some sort of dungeon.’

A row of oak doors pierced the wall, studded with wicked-looking lumps of iron and hung with heavy bolts. All the doors had grilles in them, presumably so that in ages past jailers could check on the miserable wretches in their charge. Nick went to the nearest one and peered in.

A body lay sprawled on the floor, arms outstretched in a pool of blood.

In that instant, all Nick’s nightmares, all the fears he’d stifled, struck him in a single, shattering blow. He sank to his knees and puked. Everything was wasted.

But even in his despair, he knew something wasn’t right. He pulled himself up and forced himself to take another look, peering through the bars into the murky cell.

Fear had played him false. It wasn’t Gillian.

The body was wearing a long white gown, which explained part of his mistake – he’d thought it was a dress. Blood covered half the face, which had also misled him. But there was no way it was Gillian. It was a man, a monk in a cassock belted at the waist with a twist of rope. Nick could see the brow of a tonsure just above the single bullet hole that pierced his forehead.

Relief flooded through him so fast he almost puked again. He forced himself to think. The blood looked wet – the puddle was still spreading at the edges. Whoever had done it couldn’t have gone far.

In the corner of his eye, he saw Emily coming up behind to take a look. He pushed her back.

‘Don’t.’

Emily shot him a searching glance, but stayed back.

He moved on to the other doors, steeling himself for more horrors. Thankfully, there were no more corpses. One room was stacked with oil drums, which struck Nick as dangerous in a castle housing a medieval library. He could smell the vapour leaking out through the grille. A second room was lined with steel bookshelves. The next room was empty, though dark stains splashed the wall. How old were they?

Nick approached the last door. His wet trousers clung to his legs, trying to hold him back; the adrenalin was draining out of him. A voice in his head screamed at him to retreat. He looked through the grille.

A young woman sat on the floor, her head pressed against her knees. Her hair hung over her face, and her bare arms were mottled black with bruises. She must have sensed the motion by the door. She looked up.

‘Nick?’

LXXX

Mainz, 1455

‘You cannot come in.’

Fust’s eye stared at me through the window in the door, pressed so close that his knotted skin seemed cut from the same timber.

I didn’t understand. ‘Is this a joke?’

‘You have broken the terms of our contract. I am calling in my loan.’

I still could not comprehend it. Like a chicken strutting around the farmyard spouting blood from its gizzard, I carried on as if it were a reasonable discussion.

‘How much do you say I owe you?’

‘Two thousand gulden.’

I laughed wildly; I did not know what else to do. ‘You know I cannot pay. Every penny I have is tied up in the Bibles. Every scrap I own is mortgaged against them.’

The eye surveyed me dispassionately. ‘If you cannot pay, then you forfeit everything. I will take over the works and finish the Bibles myself.’

‘How can you?’ A thousand questions distilled into one. Fust chose to answer its narrowest, pragmatic meaning.

‘The men know who pays their wages. They will see the work through. I will meet you tomorrow to discuss it.’

He snapped the window shut.

Ten years of hope died in an instant. I slammed my fist against the gate so long I almost unhinged it. I denounced Fust to all the powers of sin and the devil, while passers-by gathered in knots and stared. No one took mercy; no one came out of the Humbrechthof, though every man inside must have heard me.

When I had spent every drop of my rage, I crept home.