In the early years, there were rumbles about the prison management being too lenient to deter repeat offenders, but Agnes sees nothing of this. The gaol seems as cold and sterile as the interior of the Dead Room; from the morose demeanour of the staff to the harsh clang of metal doors that sets her teeth on edge.

It is fortunate that Simon accompanies her, because without him nothing about this miserable kingdom would feel real. She is painfully aware of her throat, and a blockage within it like a wad of cotton. Every instinct recoils and urges her to run. But this is the last place a person can flee from.

The visiting room is packed with desperation. Coarse, rough-featured women cling to the chaplain and must be prised off; another, more genteel-looking creature sits listening to a lawyer with her head in her hands. There is no prevalent age group. Agnes is surprised by the number of women older than herself. Villainy, it seems, is not something one grows out of.

She thinks of little Pearl, who will never age now, and her empathy for the prisoners withers, replaced by a cool fury. If Agnes were to look in the mirror, she feels sure she would see the flinty expression of Constance staring back.

The warden makes them sit in front of a small desk. The chairs are battered and unsteady; Simon’s squeals under his weight. She had hoped they would only be permitted to see the prisoners through bars; in this chamber, there seems so little standing between her and evil.

Boots crunch on the floor beside them. A turnkey with a heavy brow hauls a prisoner to the opposite side of the desk; it takes Agnes a moment to realise that it is Miss West.

Prison has sucked the glamour from her. Her flaxen hair is shorn and concealed beneath a cap; only a hint of her widow’s peak shows at the brim. She wears a dingy prison uniform that dulls the lustre of her eyes.

‘Strike me blind,’ she laughs as she is pushed into a seat. ‘You came.’

Agnes cannot speak; contempt almost chokes her. The way the young woman leans back in her chair and crosses her arms is not just insolent, it is heartless. She is still putting on a show: the unrepentant sinner.

‘Miss Darken has called upon you, despite her ill-health, as an act of charity,’ Simon announces sternly. ‘And she hopes to encourage compassion in you likewise. Will you not admit to all your atrocities, Miss West? What about Mr Boyle, Mr Lewis and Commander Hargreaves?’ He spreads his hands. ‘Come, let us bring this awful matter to a conclusion. Give the bereaved families the comfort of knowing that justice has been served.’