In regards to my covetous nature, I blame my given and family names: Jules Pfennig. Jules, a sound that conjures an image of gemstones. Pfennig, from German, meaning a mere penny. I have passed my life suspended between aspiration and deprivation. So, when a certain individual offered me an opportunity to lay my hands on a gem of great value, he roused my interest.

Allow me to set the scene. After my most recent outing, one wherein I exposed the secret behind a supposedly miraculous bell, I returned near midnight to my flat at 223 Baker Street only to discover my door ajar and an intruder sitting behind my desk.

At first I thought my visitor, ensconced in shadows, must be my neighbour, Sherlock Holmes. I've had a feud with that impudent detective—he being jealous of my investigatory skills and rankled that my talents were luring away his patrons. Yes, I have represented myself to potential clients as being the Sherlock Holmes, but when my inquiries led to success weren't they giving him the credit? He should be thanking me.

The uninvited stranger spoke in an icy voice, "Mr. Jules Pfennig." I felt unnerved that he knew who I was: the invasion being ever the more personal. "I am James Moriarty."

The room was chill, but not cold. Nevertheless, he was bundled in a dark grey greatcoat with a navy blue scarf knotted around his neck. He had a hawkish look, or better said, that of a vulture in the way he craned his neck forward. His mostly bare skull appeared swollen, his brain prepared to burst out. His hands rested on the desktop, his fingers curved like claws. He informed me he was a former professor of mathematics. "But I am not here about maths." I heaved a sigh of relief. "Do you know what a carbuncle is?" he asked.

"Of course, I do." When I was but a sprout, I made a few extra shillings by scraping the bottoms of boats. I didn't bother to tell him they were correctly called "barnacles."

Would you have any compunctions regarding stealing the largest, most valuable carbuncle in toto mundo?"

"Compunctions? I don't know the meaning of the word." I remembered they were some sort of punctuation but that bit of knowledge merely served to further confuse me. In toto mundo? Did that mean naked? And how valuable could a barnacle be? What was he talking about? This man with his vast vocabulary was either a madman or some sort of indecipherable genius, the Napoleon of bulgy heads.

"No compunctions, excellent," Moriarty remarked. "A man who has broken free from the trivial shackles of right and wrong has an advanced mind, indeed."

When in doubt, always agree firmly. "Trivial shackles. Precisely."

My advanced mind was exhausted. As I had mentioned, I had just returned home and it was late at night. I was desperate for sleep and this encounter felt unreal. Being lit by a single flickering candle on the nightstand by my bed, my room seemed unfocussed, like a half-remembered dream. With Moriarty in the shadows, when he rose from his chair, he seemed to float. I had to force myself to envision legs and feet fixed to his fearful form.

"What if I were to tell you that the theft will be perfectly legal?" he said.

Lawful larceny? Hmm. I licked my lips. "I'm listening."

"A jewellery concern in Hatton Gardens, Morgan, Stern, and Morganstern, keeps the Black Carbuncle, a spectacular dark red ruby, in a special display case in the centre of their store. They use it to advertise the prestige of their business and to lure in the curious as prospective patrons."

Aha! The Black Barnacle was the name of a ruby. But of course! Much the same as the priceless jewel in The Moonstone, the mystery novel that first inspired my lust for detection, did not come from the moon. A surprise twist!

"The firm has asked me to test their security. I will pay you to snatch the gem, make your way to the street, and pass it to me and my associate, Sebastian Moran, in a waiting carriage. Your task completed, surrender yourself to the police. Once we have shown the jewellers just how easily the stone can be appropriated, we will arrange for the authorities to release you." He said the last part fluttering a hand as though describing a mere afterthought.