From this distance it looks pedestrian, blending in seamlessly amongst its limestone companions. No passer-by would suspect that ghouls swarm inside. It is a kind of ossuary, she thinks, holding captive the bones of an albino child and a man with phossy jaw. This is what her beautiful city has come to: the beau monde and the dandies have fled, leaving only the spinsters, the soot and the ghosts behind.

She tucks a damp strand of hair behind her ear, and notices with a jolt that her left hand is bare of all jewellery. Of course, Montague’s ring must still be on the floor where it fell in the upstairs room; she did not have time to collect it before Miss West threw her out. She has worn the ring on her finger for all these years; it seems strange that she did not miss it until now. Perhaps hearing Montague’s voice at the séance is finally helping her to move on. But she would feel better if she knew what had made his spirit so afraid. Or who. What were his last words? She’s coming. Was he referring to Miss West, on the stairs? Or was he trying to tell her that the killer is in fact a female?

Agnes cannot ask him now. She has promised Simon.

Finally, the front door opens. Agnes turns to the side, letting her bonnet shield her face, and dips the umbrella a little lower. She is right to do so. Miss West leans out, casting her suspicious eyes up and down the street.

Satisfied, she calls over her shoulder – probably a warning to Pearl – and leaves the house. But then she performs an action Agnes has not noticed her take before: she turns and locks the door behind her.

‘Chestnuts all hot, penny a score!’

Miss West walks straight past the man hollering his wares and weaves effortlessly around a costermonger’s barrow. She has only a bonnet to cover her, but she does not bow her head under the rain. This is a woman who knows where she is going and will not let anything stop her from getting there.

Agnes watches her stride off towards Cornwell Buildings, where she is swallowed in a forest of umbrellas.

The shop bell jangles behind her. Simon emerges from the chemist’s with a bottle and a brown-paper parcel.

‘The sister has departed,’ she tells him. ‘We must move quickly.’

A boy does his best to sweep a path for them across the road and Simon tosses him a penny.

The rain has failed to wash the sooty fingerprints from the window of Pearl’s house, but Simon is able to read the advertising cards aloud.

New and scientific treatment

The Magnetic Touch for chronic disease

No medicine given

No pain caused

The White Sylph

Conductress of Spirits

Blessed with the gift of trance-mediumship

Enquire within

He raises an eyebrow at Agnes.