Miss West chuckles. ‘Ah. You didn’t read the card in the window, then? This is a special house.’

Agnes sips at the water, giving herself time to think of a response. Either she has lost her wits, or Miss West has. Given her fainting fit, the former seems likely.

‘Special how?’

Miss West considers. Just when Agnes thinks she will not answer, she says, ‘Tell me, ma’am. Would you like to speak with your dead sister?’

‘Good heavens, no.’ She drops her cup. Miss West lurches forward to save it, her brilliant eyes widening.

‘Careful. I didn’t mean to scare you. I know it ain’t for everyone.’ She hands the glass back to Agnes. ‘I was just trying to explain what we do here. I read auras. Cleanse and heal them with my Mesmerism. That’s not much good to you. But the Sylph … I thought the Sylph might be able to help.’

Agnes struggles to get her bearings. Sylph … she has heard this somewhere before. But it does not help her make sense of the strange words this girl is saying. Mesmerism? Was that not proved to be quackery? She remembers Simon speaking of it once, after he attended a demonstration. He had been impressed by one aspect, although she is at a loss to remember what …

‘The truth is, ma’am, that I can’t help you identify your friend. You’ll have to go see the corpse, or else wait until someone else does. That might take months. Or’ – she looks straight into Agnes’s eyes, unabashed – ‘the other way. We ask the man himself.’

‘I do not have the pleasure of understanding you.’

Miss West points. ‘Behind that door, asleep, is the White Sylph. She can speak to the dead.’

Prickles run all over Agnes’s skin. The White Sylph. She remembers now: Mrs Boyle. Mrs Boyle spoke of contacting her murdered husband through a spirit medium of the same name.

It all crashes together in her head: the large cabinet, the crystal ball on the table. Necromancy.

‘I …’ she begins, but it transpires there is no adequate response when people talk of communing with the dead.

Can it really be possible? Can it?

Agnes imagines skeletons, ghosts and ghouls. The pictures fill her with an abject, quivering dread, until she thinks of Papa and her heart stutters. If it was true … If she could actually talk to him, one last time …

She clears her throat, raises herself to a higher position. ‘I thought you said that your sister was unwell, Miss West.’

‘She is,’ Miss West agrees. ‘The Power comes after a spell of bad illness, and it can make you sick, too. That’s the price you pay for the Gift. But in a few days I’m sure she could do a séance for you.’