A short time later, they were shown inside, through a neat hallway into a bright parlour at the back of the house. Sarah surveyed it with a maid’s eye for what might have been urgently tidied away, but nothing leapt out at her. Her gaze was more pressingly drawn to the herb garden she could see through the window, as the relationship between plants and medicine had become a passionate area of study. The beds looked carefully tended. She spotted mint, sage and rosemary as well as yarrow and comfrey, suggesting that whoever tended this garden shared her interest in medicinal plants. There was one plant which looked familiar that she could not identify.

‘Is Mary expected home soon?’ Sarah asked as she took a seat.

There was uncertainty in Martha’s expression, as though she was not sure quite how to answer.

‘She tends to reside with the patients she works for,’ Martha said. ‘She left a few days ago to take up a new appointment. I do not know how long she will stay.’

‘Do you know where this appointment is and who it is with?’

Again the uncertain expression.

‘She does not always discuss these matters with me. Suffice to say she comes and goes, but I seldom have notice of either. What is this matter you wish to discuss with her?’

Raven sat forward in his chair, that eagerness animating him once again.

‘We have reason to believe that three of the patients she recently attended might have died from the same illness. We are concerned that she is at risk from it too, or that she may somehow be unwittingly instrumental in transferring it.’

Martha visibly bristled at this last, and rightly so. Raven really ought to have phrased this more delicately, but his enthusiasm for his theory over-rode such considerations.

‘My sister is an excellent nurse, and much sought-after,’ she said. ‘I am sure nothing that she did would have played a part in this.’

Sarah knew she had to ameliorate the situation, and quickly.

‘Mary’s reputation indeed precedes her. She was spoken of most highly by the doctors who worked with her in these cases.’

Raven picked up on her tone and attempted to make amends of his own.

‘Quite. It appears that these patients died of a new disease, not encountered before in this city. Mary is therefore the person best placed to provide accurate accounts of how the disease progressed in each case. She is in a unique position. She may be able to provide evidence vital to our understanding.’

Martha’s demeanour softened a little.

‘Yes,’ she said. ‘Mary did mention a young man who had died soon after his mother. She was most upset about it, as they had both appeared to grow stronger under her care, only to decline and then succumb. It was distressing for her. She is very particular in her care and takes pride in her work. We both do.’