‘Mr Wurms is working there.’ Emma pointed to the glow.

‘I haven’t seen him in the house,’ Alice said. ‘Does he live in here?’

‘Yes,’ Emma said. Whatever spirit had briefly animated her was gone, and she was back to answering in monosyllables. They walked on in silence for a few moments.

‘What do I do,’ Alice said after a while, ‘if I get lost?’ It was easy to imagine in this huge, dark place.

‘Look at the ceiling,’ Emma said.

She raised the lantern as she spoke, so Alice could see the stones that made up the roof. Something glittered among the irregularly shaped blocks – a chunk of obsidian, roughly triangular and about the size of her fist.

‘The narrow end always points towards the front door,’ Emma explained tonelessly. ‘You should always be able to find your way back.’

Unless your lantern goes out, Alice thought. But she kept that to herself.

They seemed to have walked for miles by the time Mr Wurms’s table came into view. It was set amid the bookcases, and volumes were piled up around his lamp. Beside them, in a rickety-looking chair, was a bespectacled man in a black suit.

He was middle-aged, Alice guessed, but he seemed old. His hair was still deep brown, but it had receded enough to leave him with a broad crown of shiny forehead. His face was thin and sallow, with sunken cheeks, and his hands had long, thin fingers with thick knots at the joints. He dressed in shabby black, like a clerk or an undertaker, but he sat so still that dust had settled all over him, like snow, and turned him a dirty grey. When he stirred at the sound of Alice’s footsteps, it puffed up and rolled off him in waves.

‘Ah,’ he said. His voice was as dry as a corpse. ‘Emma. And you must be Ms Creighton, though I don’t believe we’ve met.’

Alice nodded politely. ‘Yes, sir.’

‘My name is Wurms.’ He had a slight German accent that turned it into Vurms. ‘Otto Wurms. It’s a pleasure.’

His tongue, shockingly soft and pink, rasped across his dry, cracked lips. The thick glass of his spectacles turned his eyes into huge, distorted pools, but she could nonetheless feel something unpleasant in his gaze. It felt . . . hungry, somehow. When he smiled, she could see his black, rotten teeth.

Alice decided she did not like Mr Wurms.

She cleared her throat. ‘Mr Black said you needed some help?’

‘Yes.’ He turned his gaze away from her with some reluctance and pointed off into the shelves. ‘There’s been another collapse. The rot gets into the shelves, you know. Mr Black has promised me he’ll see about getting another set, but in the meantime I need you to bring all the books back here. We can’t have them lying on the floor, can we?’