Agnes turns the paper over for the girl to see. Freezes.

There is no mistake, small and faint as the profile is. Mrs Campbell was right: it is not Lavinia.

The physiognotrace has drawn Constance.

‘That’s adequate for me,’ Lavinia yawns. Her perfectly manicured fingers tug at the paper but it is a moment before Agnes can force herself to let go.

What is happening? How is this possible?

‘I will enlarge it, cut it out—’ she starts but Lavinia waves her off.

‘Really. Do not trouble yourself.’

Mrs Campbell sniffs. Her mouth has pinched, highlighting the wrinkles around it. ‘I did have something better in mind. I take it you will not be using that incompetent contraption for my own shade.’

‘No, no.’ Agnes hurriedly pushes the physiognotrace aside, disengaging the pole and propping it up in the corner. ‘I did not wish to use it in the first place. Please, have a seat. I will … Let us use paint! I will paint your silhouette onto plaster, how about that?’

She hopes her hand will be steady enough. The prospect of four and six seems to be drifting further and further away.

Why Constance?

She cannot begin to comprehend how a machine, an actual machine, could make this error. Her own hand might cut something from memory, yes, if she lost concentration. But the physiognotrace? She is tempted to take the paper from Lavinia and pore over it, see whether her eyes were mistaken.

It must be the séance – all that talk of ghosts is making her see them everywhere.

Mrs Campbell spreads her skirts and descends upon the chair.

Agnes gathers her apparatus: not really paint but India ink, water and soot blended together to make the perfect consistency of black, and a white oval of plaster for the background.

Her trembling fingers select a round, soft brush. Then she begins to work.

It is soothing. With scissors, she is forced to cut away from her body, but now she can pull the brush towards herself. The lines are soft, oily smears. There are two edges to her brushstroke and she focuses on the left, the clearer one, ignoring the other that encroaches into the white space she will later fill.

Forehead, nose, mouth, chin.

These are not Constance’s features. She makes sure of that. But the machine’s drawing still flashes before her. Impossible, as were the things she saw in Miss West’s parlour on Walcot Street.

Perhaps this is what happens when you meddle with the natural order. She did not stop to fully consider the consequences before she called up spirits, but of course it makes sense: if one ghost can wander, surely they all may.

Constance always wanted to be her only sitter.