‘A daughter, apprenticed to a weaver, and a son. You will meet him soon enough. The guild has just approved his enrolment as my apprentice. You will share the room.’

We reached the platform at the top of the stairs and ducked into the attic. A window in the gable admitted a cool autumn light. Otherwise the room was bare save for a lamp, a chest and a single bed.

‘This is where you and Pieter sleep.’

I crossed to the window and looked out. Directly opposite rose the half-built cathedral – the needle-thin chapel the only part rising to its full height. The city stretched away from it in a broad crescent, mirroring the bend in the river which ribboned away to the south, back to Mainz. The view reassured me. Perhaps Gerhard’s tutelage would not be such an ordeal.

The door banged open and I turned, thinking the wind had blown it in. A youth, not much more than a boy, stood on the stair outside and peered in curiously. He had soft white skin, unmarked by any line or flaw, and a cap of golden curls. For a moment I thought he must be an angel. Then I saw the resemblance with Konrad. They were as alike as two clay vessels moulded by the same potter’s hand, one fired and cracked, the other moist and smooth, untouched by the kiln. He smiled at me.

Schmidt made a gesture between us. ‘This is my son, Pieter.’

That moment, I felt the demon enter my soul.

IX

New York City

Bret’s eyes opened wider – at least he was alive. He stared out of the laptop window and jerked his head back over his shoulder. The gunman’s gaze was fixed on the door; he hadn’t noticed Nick’s face on Bret’s screen.

Nick’s mind spun; he wanted to vomit. What was this?

A door banged open behind him. ‘Nick? What are you doing?’

Nick turned. It was Max, his neighbour from across the hall, an eight-year-old latchkey kid whose mother worked all hours at some big legal firm. Nick had helped him with his homework a couple of times. He was peering out his apartment door, sucking on a soda and looking down curiously at Nick. ‘Did Bret lock you out again?’

‘I-’

Nick heard the gunshots through the wall. A split second later the noise repeated through the speakers, a digital echo almost louder than the original. By then, Bret was dead. His body convulsed under the impact of the bullets, jerky and unnatural, as if the enormity was too much for the camera’s connection. The man in the room was staring at the monitor, watching Nick on screen. For a moment their eyes met, artificially opposed in virtual space. Then the gunman moved for the door.

Max screamed and slammed his door shut. Nick picked up the laptop and ran. Sick with shock and adrenalin, he burst into the stairwell. Up or down? Downstairs was the street, people, safety – would the gunman expect that? Was there someone else waiting for him there? If he went up, would he be trapped?

The door to his apartment opened and he decided. Down. Slipping and sliding, hanging on to the rail for dear life as he corkscrewed around. He passed the door to the second-floor corridor and kicked it open, hoping to confuse his pursuer. But he was the only person on the stairs: his footsteps must have clattered all the way up to the roof. There was no way the gunman could mistake it.

Nick skidded to a stop at the bottom of the stairs. The lobby was empty, but through the glass doors that led onto the street he saw movement. A man was loitering outside, keeping just out of range of the light over the door. He had a black coat draped over his right arm, covering the hand and whatever it held.

It could have been anyone: someone waiting for his date, a smoker getting a fix, a driver making a pickup. Nick didn’t want to find out. An animal instinct seemed to have taken over. Everything else – the horror, the confusion, the terror – had been locked down. Footsteps were pounding down the stairs.

Nick threw himself into the waiting elevator. His thumb hammered on the button; the footsteps were almost on top of him.

The doors slid together with a grumble. In the narrowing crack, Nick saw the gunman race into the lobby. He’d pulled off his balaclava, revealing a closely shaved head and a row of gold studs gleaming from one ear. His head turned; their eyes met. Then the doors shut and the elevator began to rise.

He was heading for the top floor. Instinct had made the decision again, the basic desire to go as far as possible from danger. But how far was that? All the corridors were dead ends. There was a door onto the roof – he’d taken Gillian up there in the summer to stargaze, though all they’d seen was the navigation lights of planes dipping into La Guardia. But where then?

The elevator stopped. From below, Nick could hear footsteps clattering up the stairwell once more. He turned down a short corridor that ended in a door with a green FIRE

EXIT sign nailed to it. Nick slammed straight into the metal bar and barged it open. He stumbled out onto the roof.

An angry, high-pitched whine erupted behind him, the building itself protesting against his trespass. The fire alarm. When he’d come up with Gillian, they’d used a credit card and a roll of tape to disarm it. Now it was in full roar, filling the cold night with its siren. Good. Help would come, the fire brigade or the police.

But until then…

Raindrops spat against his face. A shiver of despair knifed through his body. He had come out onto a small square of Astroturf that some optimist had once laid to impersonate a lawn. All around him were the water tanks, heating vents and satellite dishes that crusted the roof. Plenty of cover – but nowhere to hide for long.

The fire alarm hammered against his ears. He couldn’t even hear if the killer was coming up the stairs. He stood there on the soggy fake grass, stiff with indecision. All his life had been based on reason: methodical, boring, safe. Now he had nothing. No framework. No time to think. Whatever instinct had driven him up there was spent. He had nowhere to go.

Strangely, in that moment of emptiness he didn’t think of Gillian, or his parents, or his sister. He thought of Bret, lying dead in an easy chair four floors below him. Bret who had told thousands of men how to go all night without ever, to Nick’s knowledge, bringing a girl back to the apartment. Bret who had bid for countless auction items he had no intention of buying. Bret who had sat with a gun held to his head and still managed to warn Nick. Buzz me.

Nick ran across the wet roof and threw himself down behind an air-conditioning unit. Puddled water soaked into his shirt. At least his coat was black. He peered around the corner, between the struts supporting a water tank.

For a moment he thought his pursuer might have given up. In the pink half-light that passed for night he saw the stairwell door swaying loose in the wind. The fire alarm wailed. The damp shirt pressed against his chest like a heart attack.

Then Nick saw him, crouched in the doorway as he scanned the cluttered rooftop. The pistol swept over Nick’s hiding place and carried on around. He was a short, heavyset man and looked out of breath. It was the first time Nick had supposed he might be anything less than superhuman.

Almost because he knew it was expected of him, Nick felt a powerful, suicidal need to run. He fought it back. They couldn’t stay like this for ever. Even in New York someone must have heard the shots, called the police.

The gunman knew it too. He edged away from the door, tracking the pistol in sharp sweeps across the rooftop, silent under the shriek of the alarm.

Then, as suddenly as it had started, the alarm cut out. A desolate silence filled Nick’s ears. Even the gunman was caught off guard. He paused, glancing around uncertainly.

Nick reached inside his coat pocket and felt his keys, cold and wet. He balled them in his fist and pulled them out. The background roar of the city at night was beginning to filter back over the ringing in his ears, but he didn’t dare risk being heard. Across the rooftop, the gunman was still edging closer.