His face was hard.

'I am sorry, Johann. This is no longer your house.'

LXXIX.

Oberwinter

The shadow under the gate was darker than anything Nick had imagined. He shivered as they pa.s.sed through it. A few paces on, he looked back. The town was already fading behind them, wrapped in mist and the safety of its walls. Inside, soft light glowed behind curtains; a Christmas tree twinkled in a window; a recorded soprano sang a lonely song. Beyond the walls, nothing but darkness.

They walked up the highway. Habit kept them pinned to the verge, though there was no traffic to avoid. Soon enough, they drifted to the middle of the road and walked side by side. Their shoes crunched in the ankle-deep snow; the shovel slithered as Nick dragged it behind him. Once or twice they heard rumblings from the river to their right, and saw lights like distant stars as barges swept past.

Nick had no idea how long they walked. On a map it probably looked no distance at all, but in that cold, monochrome world, with only his footsteps to mark the time, it seemed an eternity. Lost in his thoughts, he might have missed the turning altogether if Emily hadn't tugged his sleeve.

'Is that a path?'

They'd come to a bend where the road swung sharply around one of the mountain's flanks. Just before the turn, a lay-by had been scooped out of the forest that ran up the gorge beyond. Where Emily was pointing, a dark cleft loomed in the ghostly snow-covered trees.

Nick turned on the flashlight. Before he could look for the path, something at the edge of the road caught his eye. It was a sign, barely poking out of the snow bank that the ploughs had heaped up. Nick went over and rubbed the crust of frost off it.

'Wolfschlucht Brucke,' he read. 'Wolf's Gorge Bridge.' He looked around for the bridge, then realised he was standing on it. He peered over the guard rail and saw the yawning mouth of a corrugated-iron pipe disappearing under the road.

'I guess this is the place. That path you saw must be a frozen stream.'

They climbed over the icy guard rail and slithered down the embankment. The frozen stream led away into the forest, a narrow ribbon of white.

Nick reached out for Emily's coat. 'You don't have to come.'

She shook him off without reply and headed up the hill.

Even with the stream to follow, the woods were all but impenetrable. The forest seemed alive. Low branches snagged his shoulders, snapped into his face, poked his legs and dribbled snow down the back of his neck. Underfoot was equally treacherous. The snow smoothed out all traces of the rocks and roots lurking beneath. He didn't dare use the flashlight in case someone was watching from the castle. Even where it was flat it wasn't safe, for that usually meant they were walking on a frozen pool. Once Nick's foot went through to the ice: he skidded, flailed, and was thrown onto his back. The shovel banged on a stone. He lay there and listened to the echo clatter through the forest.

Blinded by snow and branches, they almost missed the castle. The only hint was a glimmer of light in the otherwise unbroken darkness to his right. That was enough. Nick struck off towards it, blundering through the undergrowth like a wild boar. A blizzard whirled around him; tree limbs creaked and cracked. If he didn't find it soon, he thought he might be lost for ever.

The trees ended in a rock face. Nick leaned against it, breathing hard and shivering. Melt.w.a.ter trickled down his back. The light had vanished, but if he craned back his head until his neck ached he could see stone walls at the top of the cliff, dark against the grey clouds. It looked a long way up.

There was a snap behind him as Emily emerged from the forest. She'd lost her hat; snow sprinkled her hair like diamonds.

'How do we get up there?'

Nick tried not to think about how high it was. 'Are you any good at climbing?'

'Not since I was ten.'

Gillian had been a climber, for a while at least. One of their less successful dates had been when she'd taken him to the climbing wall where she went every Wednesday. She crawled up to the ceiling like a spider, laughing, while Nick still hadn't figured out how to put on the safety harness. When he did finally make it onto the wall about eight feet up his wrists ached for a week.

'I guess I'd better try.'

He stared at the cliff, trying to figure out how Gillian could have got up. The black rock face offered no clues. He ran his fingers over the surface to feel for a crack or a ledge, anything to get him started. A small bulge, about knee high that might do.

'Here goes nothing.'

He put his foot on the outcrop, pushed off and lunged up for a handhold. All he felt was gla.s.sy ice. He scrabbled for purchase and got none; lost his balance and fell to the ground. The snow probably broke his fall, though it didn't feel like it.

Emily leaned over him. 'Are you OK?'

He brushed himself off and got up. 'Gillian wasn't a mountaineer. Even she couldn't have climbed a sheer ice face.'

He went back to the cliff and examined it again, brushing his hands over it in broad sweeps. Emily hung back. She fumbled in her pocket and examined the sheet of paper Gillian had left, now creased and damp from the snow.

'Maybe she didn't go up.' She tapped Nick on the shoulder and pointed to the paper. 'Mariannenbad means Mary's Pool. And the book in the restaurant said there was a shrine to her near the medieval monastery.'

'You think Gillian prayed her way in?'

'Marian shrines were often built over springs. They thought the water had healing powers.' Emily's words sounded quiet under the snow, as if the trees themselves were listening. 'We came up a stream bed. It must come from somewhere.'

They scrambled around the base of the cliff, wading through the deep snow. It looked so permanent. Any holes or caves must surely have been filled in weeks ago.

'What's this?'

There was hope in Emily's voice. Nick hurried over to where she was standing. Shading the beam with his hand, he shone the flashlight on the rock.

'Looks like some sort of landslide.'

At the foot of the cliff, a small heap of rocks spilled out across the ground. The snow that covered them was thin and broken, sinking into a shallow depression that snaked away from the cliff. When Nick put his foot on it, he felt ice.

'Here's our stream.'

Emily was already clambering up the rock fall. Lying flat, pressing her belly against the stones, she scrabbled the snow away.

'I think-'

There was a clatter, and a stifled gasp as the stones shifted under Emily's weight. She rolled back. Nick lunged forward to catch her.

'Are you OK?'

She brushed herself off. 'I think there's a hole up there. It's covered over, but the snow's not deep.'

Moving cautiously, Nick scrambled up the rocky slope. A couple of times the stones almost gave way under him and he stopped, his heart in his mouth. But Emily had been right. Between the top of the debris and the cliff face, there seemed to be a gap. Nick burrowed into the snow, scooping it away with the shovel. There was nothing behind it. When he stuck his arm in up to the elbow he felt only air.

Emily gazed up from the bottom of the slope. 'Can you get through?'

Nick felt around. 'Only one way to find out.'

Even with all the snow cleared out it was barely high enough for him to squeeze through. Rocks sc.r.a.ped his cheeks; snow dribbled down the back of his neck. He wriggled through on his belly. It was deeper than he'd expected; there was a moment when his whole body was under the cliff, and he had a sudden, paralysing vision of the stones giving way and crushing him.

And then suddenly the ground was dropping away. Nick pushed out an arm to steady himself but found nothing to hold. He tumbled down the slope in an avalanche of stones and bruises, until he landed with a splash and a thump on a hard floor.

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. Stalact.i.tes 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 coa.r.s.e, 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 stalact.i.tes 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 ca.s.sock 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?'

Lx.x.x.

Mainz, 1455

'You cannot come in.'