Pearl squints and lowers her chin to protect her eyes. ‘There’s no kindling,’ she squeaks. ‘There’s nothing in that fireplace.’

But they can hear it crackle and pop.

The dark patterns begin to take form: they flatten out, grow edges, spread into faces – no, profiles. They are shades; the shades Agnes has cut with her own hands. Astonished, she watches them flick past as quickly as the pages of her duplicate book.

The Carfax children, Montague, Mr Boyle, Ned – and other faces with names she has long forgotten. Was that Mrs Campbell, there? She cannot be sure, the images are cycling by so fast …

But the last shape she knows.

It flickers, suspended, as if held underwater.

‘Constance?’ she cries.

Soot rattles down the flue, raining black over the flames. Constance’s profile breaks and scatters.

As quickly as the fire burned, it winks out.

The room falls into darkness and whoever it was – whatever it was, it has gone.

Pearl releases her hands. Without their support, Agnes topples.

‘Careful!’

She catches herself just before she meets the floorboards. Her arms shake under the strain; her knees feel like they have had knitting needles driven through them.

‘Here, let me help you stand up.’

Looking at the room, Agnes can barely credit that any of it really happened. The house around them seems tranquil. Their noise has not awoken Miss West or the neighbours.

Pearl steals up to the fireplace and pokes one of her fingers into the ash heap.

‘It’s cold,’ she marvels. ‘How can it be cold after that fire?’

The entire place feels cold to Agnes, even though she is slick with sweat. She keeps seeing the way those flames rippled, more like water than fire, and Constance’s face beneath the river.

‘Are you sick, ma’am? It’s usually me what gets ill after a séance. Take a big breath. I’d give you a glass of water if I had any.’

At the mention of water, Agnes shakes her head.

‘Who …’ Pearl starts cautiously. ‘Who’s Constance? You called out her name. Was that your sister?’

‘Yes.’

‘How did your sister die?’ Pearl whispers.

Agnes closes her eyes. ‘She …’ She is about to say drowned, but she bites the word back. That is only the socially acceptable version of the story. This girl who has hidden her all day and risked so much for her sake deserves honesty.

‘No one was able to tell us exactly what killed her. Whether it was her injuries or … You see, there was … an accident. We were in a carriage when the horses bolted. It ended up in the river. They say my friend Simon rescued me but I cannot recall that. I lost consciousness underwater. When I came to myself, I was safe and Constance was … gone.’

Pearl clutches her hand. ‘I’m sorry.’