Even so, this incident served as a warning. When next I wished to keep a patient longer, I knew I could not rely solely on presenting falsified documentation of troubling symptoms. I would have to induce them.

I administered doses of medicines that made my preferred patients demonstrably sick when they were due for examination. It was easy enough to do. It proved evidence enough to satisfy even the like of Dr Hewitt.

More so than when I merely altered the ward journal, I marvelled at the effects of my actions. It appeared I had the ability to bend matters to my will simply by the administration of medicine. It created in me an ever-deeper curiosity, an insatiable thirst for greater knowledge.

I watched the doctors carefully. It seemed to please them that I was showing such a keen interest by asking them about dosages and the effects of the various pills and potions that they prescribed.

There was a limit to how much first-hand experience I was permitted, however, which was why I liked being on the ward at night. With the doctors largely absent and nurses sparsely spread about the hospital, I was free to experiment. I dosed patients with morphine in ever-increasing amounts and paid close attention to the results. I watched as their breathing slowed and their pupils shrunk in size.

The next station upon my journey was marked by a dock-labourer from Leith by the name of John Robertson. He sustained a burn to his upper chest on account of sleeping too close to the fire while under the influence of ardent spirits. The burn extended to the front of his neck and caused him to experience a restriction in his breathing, for which he was prescribed warm-water dressings and morphine three times a day. I gave it more frequently than that, watching as this brute of a man became drowsy and incapable.

In the midst of my experiment I was called away to assist another patient who had had a seizure, and when I returned, I found that Mr Robertson’s breathing had stopped altogether, and he was quite dead.

I did not mean to kill him. But nor did I have any regrets about having done so. Rather, I felt powerful that I had wrought this. A man so mighty, felled by my small hand.

That sense of power only increased the next day when his newly widowed wife came to claim his remains. I watched her weep and wail, this gushing, uncontainable outpouring of grief. A drastic change had been wrought upon not one but two people: one life ended, the other altered for ever, and all of it precipitated by actions that were unknown and unsuspected.