‘Phosphorus can be a poison,’ Simon counters. He is trying to be amiable to gain Pearl’s confidence, but Agnes knows him well and can hear the concern in his voice. He is grieved by the sight of this waif she has produced. ‘That is the substance your father used, to make matches for his employer. The phosphorus has hurt his mouth.’

‘We give him magnetised water to drink. Myrtle’s going to exchange his bad energy with hers. She’s strong, she’s got the vit – vite – vitality.’

‘Good. That’s good.’ He balls a hand by his side, the only indication of his outrage. ‘Miss Meers, I would like to take a look at your father and see how he gets along. I will not hurt him, I promise. I will not administer any medicine or even touch him, if you do not wish it.’

The little body retracts like a concertina. ‘He did say … he always wanted to see another doctor. But Myrtle wouldn’t let him, after the first one sent us here to Bath …’

Simon nods, rises awkwardly to his feet and offers her his hand. Pearl accepts it like something that might burn her.

Agnes trails them into a chamber at the end of the corridor, which is about the size of a small parlour – an innocent-looking room to be the source of the rot she has smelt since the first day she entered the house. The stink here is not just humming but festering, choking the breath from her.

‘Miss Darken, this is not a sight that—’ Simon begins.

She wonders what end he intended to put to that sentence, for there is not a word adequate to describe what lies before her. That is cruel; she should say who lies before her, but in all honesty she is struggling to identify the person on the narrow bed.

He is too horrible to concentrate on for any length of time. The wasted, skeletal body she can just about stomach, but the lower half of his face is dribble, corroded flesh and gaps where no gaps ought to be. Perhaps the worst circumstance is that his eyes, nose and forehead all look perfectly regular. It is only below them that he becomes a puppet with a wide, oozing grin, the teeth poking out at angles.

Has such a spectacle been a normal, everyday sight for a young girl like Pearl?

‘I will help,’ she murmurs, hardly knowing how.

Of course Simon is more practised. ‘Mr Meers?’ he asks, approaching the bed. ‘My name is Dr Carfax. With your consent, I should like to examine your jaw.’

The man blinks, struggles to focus. When at last his brain registers who Simon is, he gives an approximation of a nod. One atrophied hand motions to his face. The gesture is crude, but understood. Cut it out.