He was right: Martha had been useful to Mary. But only in death. After Mrs Dempster died, they had moved from Canonmills to Lochend: somewhere isolated, where nobody would know or recognise them. At some point after that, Mary had killed Martha, then assumed her identity; and with it not only her money, but the status and respectability her name conferred. But she separately retained the identity of Mary, having a professional reputation to trade upon: a means by which to gain access to patients.

She switched between accents and must have switched between appearances too. That was why Martha always seemed so insipid: she was a cypher, a mockery. That delay in answering the door, after Sarah spied someone in the window: she had seen unexpected visitors and needed a few moments to transform herself, then further time to ensure nothing was on display that shouldn’t be.

Believing he was speaking to Martha, Raven had told Mary directly that she was under suspicion, and subsequently he had kept her informed of everything he had discovered about her. Then she had fed him evidence of her own guilt, intending to shed her compromised persona like a snake its skin.

Mary was Martha. Martha was Mary. And Raven had left Sarah with her, utterly defenceless.

SEVENTY

er memory was fractured. What used to be a path connecting moments had become a random series of discrete fragments. She remembered walking back from Stockbridge, the conversations she had that day jumbled and out of sequence. She remembered feeling weak, collapsing at her door. That was when what used to be linear had become splintered, the stained-glass windows of her mind shattered and transformed into a kaleidoscope.

She knew Raven had been there, but it felt like he was behind a gauze. Sometimes she was aware he was close by, but it was as though she could not break the surface to reach him. At other times, she felt his presence, but would open her eyes and find only Mrs Sullivan, or Martha.

She had heard him, but she was not always sure she had spoken in reply. She could not distinguish between words she had merely thought and what had issued from her mouth. Raven seldom answered her, merely told her to rest. Had she only dreamed her questions, or was there something he did not want to say?

She had been given chloroform, after that perhaps morphine, but she knew enough to understand that it was more likely infection that was addling her mind. She had felt the wound, touched the stitches. Raven had cut her open, and she knew why. She had been working for the Professor of Midwifery after all. That was how she knew she was dying. Raven had gone into her abdomen, an action of last resort. He had done whatever he could in order to save her, but she understood that it would not be enough.