‘No,’ Emma said, apparently unable to tell if a question was rhetorical.

‘It’s quite a load,’ Mr Wurms said. ‘You’d do best to fetch the trolley.’

With that he turned away, back to his reading, as though the two girls were an electric light he’d switched off. Alice wanted to say something, just to make him turn round again, but she thought better of it.

She turned to Emma. ‘Come on. We’d better get to work.’

The trolley was an ancient, squeaky-wheeled monstrosity that required both of them tugging to steer. It seemed almost sacrilegious to push the rattling, screeching thing through the deadly quiet of the library, and Alice fancied their progress was preceded by a vanguard of fleeing cats. Following Mr Wurms’s directions, they found a place where an ancient set of shelves had given way under the weight of books, spilling fragments of rotten wood and hundreds of volumes across the stone floor.

When she saw it, Alice sighed. ‘This is going to take all afternoon.’

Emma didn’t express an opinion one way or another, just set to work picking up the fallen books and stacking them in piles on the floor. Alice hesitated for a moment, distracted. She felt a peculiar itch between her shoulder blades, an odd sensation of being watched. Something moved, at the corner of her eye, but when she turned to look it was only a thin grey cat, slinking through a gap between the shelves.

‘There’s no percentage in hanging about,’ she said aloud. It had been something her father had told her, whenever he’d needed to get her moving; she’d said it automatically, but the memories it called up made her chest clench tight. She squeezed her eyes shut for a moment, then forced herself to take a deep breath. Maybe if we finish early, I can ask Mr Wurms if it’s all right to take something back to read. ‘All right. Try and pick out the biggest ones first, we’ll need to put them on the bottom.’

Emma followed Alice’s instructions dutifully, and once she’d got started, she worked tirelessly. The biggest books were a set of huge, linen-bound folios, yellowed and musty with age, which the two girls extracted and laid on the trolley like foundation stones to support the rest of the pile. It was heavier work than Alice had expected, and after an hour her back was aching. Her blouse was damp from the exertion, and the dust mixed with sweat to form a grey paste that covered her skin like the marks of some horrible plague.

And someone was still watching her. She was certain of it, in the pit of her stomach, but no matter how fast she turned round, she could never catch a glimpse of the observer. She wondered if it could be Mr Wurms, secretly checking on their progress.

Probably, she thought, it’s just the cats.