‘Miss West!’ Anger and disgust squirm within her. ‘How dare that woman ask anything of me? She is a monster!’

He tilts his head, appraising her. ‘A monster? Do you think so? I am wary of judging her as such. From what I can gather, she was deeply unhinged by grief. She lost her parents at a young age and was put under intolerable pressure caring for a newborn. It does not excuse her behaviour, precisely, but I have seen too many cases of imbalance not to feel a modicum of pity.’

Agnes always knew that Simon was a worthier person than her, and this only goes to prove it. She may have sympathised with Miss West on that first visit, long ago, but she certainly does not now. ‘Her actions were calculated, Simon. She used the poison deliberately, to deceive and make money. Fools like me really believed …’

‘I have met at least one woman of a darker disposition,’ he says sourly.

She chews her lip and considers. What strikes her is not his veiled reference to Constance, but the thought of the phosphorus. A sharper eye may have noticed that the glow surrounding Mr Meers and his daughter was suspiciously similar, but that is not all she founded her faith upon.

‘You are right, in one respect, Simon: I do need answers. It does not make sense to me. Pearl was not party to the phosphorus deception, I am sure, yet she said remarkable things … She manifested such believable symptoms … There must have been some truth in her power. I do not think Miss West’s abuse can explain Pearl’s behaviour at the séances.’

‘It can, though,’ he says sadly, folding his hands behind his back. ‘Miss West is a practitioner of Mesmerism. While that discipline is perfectly useless in curing physical ailments, it can readily supply a range of tricks. I have seen them myself in lectures. The mesmeric trance is a state of altered consciousness, Miss Darken, and it seems that your young friend was particularly susceptible to it. She was completely in her sister’s power. All Miss West needed to do was put her in a trance each morning and instil the things she wanted Pearl to see, say and do. She may even have trained the girl’s unconscious to respond to certain cues and stimuli. It is impressive, in its way. Beyond the powers of an ordinary match girl. It is a shame Miss West did not put her talents to better use.’

‘But …’ Agnes stops and bites back her words. Simon sounds so certain that it was an elaborate hoax. No doubt parts of it were: Pearl’s unearthly lustre, the rocking table, the information about Commander Hargreaves taken from the newspaper and gingered up with the imitation of drowning.