She would do what she was asked, quickly and without hesitating, and was capable of executing quite complicated tasks flawlessly. She could read and write – Alice watched her go through a stack of newspapers for Mr Black, page by page, noting down some detail from each into a little notebook. And she was unfailingly polite, even when Mr Black fumed and glowered.

But she seemed, for lack of a better word, empty, like the house itself. A friend of Alice’s father had described someone by saying: ‘The lights are on, but no one’s home.’ In that case, he’d merely meant the poor man had gone mad, but it seemed to Alice that this was more literally true as a description of Emma. When no one gave her anything to do, she would simply do nothing, standing in the front hall or sitting alone in her room for hours without any sign of discomfort. She was more like a mechanism than a person, Alice thought, and wondered if there was a secret catch at the back of her head that would open up her skull and reveal whirring gears and pistons.

Emma was a servant, in that she did what Geryon or Mr Black – or Alice, for that matter – told her to do, but she didn’t do what Alice thought of as servants’ duties. As far as Alice could tell, no one did, and yet things did get done, in a clandestine way that started out creepy and ended up as plain infuriating. There were no cooks in the kitchens, but meals were laid out on the table when she arrived and whisked away when her back was turned. When she returned to her room in the evening, the linen had been laundered and the bed made. The floors were always mopped, the windows scrubbed, the gaslights cleaned and lit and the lintels dusted. But it all happened out of sight, when she wasn’t looking, and no matter how fast she raced from one room to the next or how suddenly she turned round, she could never catch any of the mysterious cleaners at work.

It felt like an enormous practical joke, or possibly a determined effort on the part of whoever it was to drive Alice insane. The suspiciously mindful silence round every corner made her want to run through the house screaming, fling her dishes against the wall, or break some windows, just to see what would happen. She didn’t, of course, because her father hadn’t brought her up as the sort of girl who broke windows, and also because she was gloomily sure they would only be made whole while she wasn’t watching.