‘She wouldn’t take her medicine because she said it was making her sick. She didn’t understand that she was already sick and even if it tasted nasty, the medicine would make her better.’

‘I see.’

As did Raven. Finally. Belatedly.

Iain glanced back to the garden.

‘If that is all, I ought to return to my labours. I am sorry I could not assist you.’

‘Not at all,’ Raven told him, the words catching in his throat, but not for the reasons that might be assumed. ‘Thank you for your candour at such a difficult time.’

They watched him walk away with a heavy tread. He looked weighed down, and small wonder, but he had no notion of the burden he had just passed to them. The man had been more helpful than he could possibly know, and certainly more helpful than he could be permitted to know. Raven suspected that it was only for that reason that Sarah was able to wait until he was out of earshot to announce her vindication.

‘The trail left by Mary Dempster grows ever longer. Do you still think she is transferring some morbid principle to these patients on her hands?’

Under the circumstances, she at least had the decency not to sound proud.

‘Her hands are almost certainly responsible, but not in the way I had envisaged.’

‘I trust you are no longer optimistic about diagnosing a new disease?’

‘No,’ he conceded. ‘I think we can add Raven’s Malady to the list of fatalities attributable to this Mary Dempster.’

‘I shudder to think just how long that list might be. She must have been working as a nurse for at least a decade. How many patients might have died leaving nobody the wiser to her being the reason why? We must tell someone: Dr Simpson, or James McLevy.’

‘Not yet,’ Raven cautioned. ‘If word gets out that a nurse has been murdering patients – whole families, even children – then there will be mobs on the streets. We don’t want every nurse who ever lost a patient to be held accused by angry relatives.’

‘She must be stopped, though.’

‘As soon as possible, but to do that, we need more than simply to find her. We will require the strongest proof, for who will believe something so monstrous? I certainly did not before now. More than ever, we need the how and the why.’

FIFTY-FOUR

he air remained unsettlingly still and consequently there was no hint of the fog lifting as Raven proceeded alone through the city, bound once more for the cottage in Lochend. Sarah had again offered to accompany him, but on this occasion he had insisted she go back and spend the rest of her day with Archie. He left it unspoken that her time was limited and she should not waste it.