On this particular Sunday, much as he needed it, he could not afford the luxury of a recreational expedition. He and Sarah had to venture north through the murk to learn more about certain tragic events that might shed further light upon their investigations. Four deaths in one household in a matter of weeks – spanning three generations – was highly unusual and might well be another instance of the disease he was hoping to identify. If the symptoms were consistent with what had been described before, then this household could go down in history as the place where Raven’s Malady was verified. Three cases would be insufficient to convince anybody, but seven? That would be hard to refute.

Sarah had still not been dissuaded of her notion that the nurse had been taking an active role in the demise of her patients, though they were at least united in agreement that Mary Dempster might be a crucial common factor in this series of deaths. In her stubbornness, she had taken a trip to the Royal Infirmary and was still refusing to relinquish her wayward theory despite learning nothing more substantial than that Mary Dempster had been dismissed for being light-fingered; and that she might once have climbed into bed with a patient whose self-confessed delirium at the time made her the epitome of an unreliable witness.

Raven had begun preliminary work on a paper but would have to admit that a lack of primary evidence was undermining him. He cursed the fact that he had only begun to identify the illness after George Porteous died, meaning he had missed the opportunity to more closely examine a live sufferer. For now, all he had were sketchy second-hand accounts. Two of these were occluded by the fog of emotion, and neither Dr Johnstone nor Greta Porteous had been closely involved in their relatives’ care. The third witness was Dr Fowler, whose judgment was clouded by altogether different factors.

As a medical man Raven had been appalled by Dr Fowler’s obtuseness and superstition, though he suspected his disdain paled in comparison to Sarah’s. Her anger at the absence of opportunities for women to educate themselves was only matched by her resentment at the privilege and preferment extended to men she considered her intellectual inferiors. Raven had little doubt that a bumbling anachronism such as Dr Fowler would have fallen into this category; he suspected it to be a wide field, one in which he was probably included too. For that reason, he would have to admit to deriving some satisfaction from setting her straight on her flawed poisoning hypothesis. She was clever, but like her revered Dr Simpson, her judgment was not infallible.