“There’s two of them about seven feet in, both of them old ’uns with a crook—I fancy they must’ve crook-hitched one another good when they met promiscuous-like, the way it must’ve been in the dark when candles were the thing—and they’re laid out in what was an underground chapel here long time ago, closed up back when all the heads was rolling and everyone was lifting toasts to Bonnie Prince Charlie and all that.”

Dickens and I stood in the dark where we were while Dradles descended another dozen steps. The chill touch of rising damp moving past our ankles and necks made my hackles rise.

TAP, TAP, TAP… TAP, TAP… TAP, TAP, TAP, TAP.

“There!” cried Dradles, his voice echoing terribly. “Hear that?”

“What do we hear, Mr Dradles?” asked Dickens.

There came a scraping and slithering sound.

“Just my foot rule,” said Dradles. “Dradles measuring in the dark. Measuring in the dark is what Dradles is doing. Wall’s thicker here… two foot of stone, then four of space beyond. Dradles hears the tap-back of some rubble and rubbish that the careless ones who interred this old ’un left between the stone coffin and the stone wall. Six feet in there an old ’un is waiting amidst the fall-down and left-behind—just lying and waiting, no top to his box. If I were to break through with my larger hammer and pick, this old ’un, bishop-hatted crook-type or no, would sit up and open his eyes and say, ‘Why, Dradles, my man, I’ve been waiting for you a devil of a time!’ And then he’d turn to powder sure as not.”

“Let us get out of this place,” I said. I meant to whisper it, but my voice sounded very loud in the winding dark and rising damp.

OUTSIDE IN THE LAST OF THE NOVEMBER evening light, Dickens paid the insolent man some coins and waved him off with thank-yous and what I heard as conspiratorial laughter. Dradles slumped away, still clutching his bundle. He’d not got twenty feet when there was a cry of “Widdy widdy wive! I—ket—ches—’im—out—ar—ter—five… Widdy widdy wy! Then—E—don’t—go—then—I—shy!” and there came an absolute hailstorm of small stones pelting around and against the grey-flannelled figure.

“What a character!” cried Dickens when Dradles and the insane child finally disappeared from sight. “What a wonderful character! Do you know, my dear Wilkie, that when I first met Mr Dradles he was busy tap-tapping away at an inscription on some headstone soon to be set in place—it was for a recently deceased pastry-cook and muffin-maker, I believe—and when I introduced myself, he immediately said, ‘Here in my world I’m a bit like you, Mr Dickens.’ And then Dradles gestured to all the tombs and headstones and headstones in the making around him and added, ‘Surrounded by my works and words like a popular author, I mean.’ ”

Dickens laughed again, but I remained uncharmed and unmoved. Inside the now-lighted cathedral, a choir was singing, “Tell me shep-herds, te-e-ell me.…”

“You know, Wilkie,” said Dickens, still in good humour despite the late hour and growing chill as a breeze came up around us, stirring the brittle leaves across the flat headstone we had dined on only hours earlier, “I believe I know the name of that choirmaster.”

“Yes?” I said, allowing my tone to convey my total lack of interest in this fact.

“Yes. I do believe his name is Jasper. Jacob Jasper, I believe. No, John Jasper. That is it. Jack to his beloved and loving nephew.”

It was not like Dickens to babble on like this, at least not with such banal content. “You don’t say?” I said, using the tone I used with Caroline when she prattled at me while I was reading a newspaper.

“I do say,” said Dickens. “And do you know Mr Jasper’s secret, my dear Wilkie?”

“How could I?” I said with some small asperity. “I did not even know of the choirmaster’s existence until a second ago.”

“Indeed,” said Dickens, rubbing his hands together. “Mr John Jasper’s secret is that he is an opium addict.”

The skin on my face prickled and I found myself standing very straight. I do not believe I breathed for half a minute or so.

“The worst kind of opium addict,” continued the Inimitable. “No laudanum or tincture of opium for Mr John Jasper, the way a civilised white man uses the drug for medicinal purposes. Oh, no! Mr John Jasper takes himself to the worst parts of London, then to the worst slums in those worst parts, and seeks out the worst—that is, to him, the best—opium den.”

“Does he?” I managed. I could feel the rising damp stealing up through my bones to my brain and tongue.

“And our choirmaster Jasper is also a murderer,” said Dickens. “A cold-blooded, calculating murderer, who, even in his opium dreams, plans to take the life of someone who loves and trusts him.”

“Dickens,” I said at last, “what in the blazes are you talking about?”

He clapped me on the back as we began walking across the graveyard towards the road where his carriage had just returned. “A fiction, of course,” he said with a laugh. “That ghost of a glimmer of a shade of an idea—a character, a hint of a story. You know how such things happen, my dear Wilkie.”

I managed to swallow. “Of course. Is that what this afternoon and evening have been about then, my dear Dickens? Preparation for one of your books? Something for All the Year Round, perhaps?”

“Not preparation for my book!” cried Dickens. “For your book, my dear Wilkie! For your Serpent’s Tooth.”

“The Eye of the Serpent,” I corrected. “Or perhaps, The Serpent’s Eye.”

Dickens waved away the difference. It was becoming difficult to see him in the growing darkness. The lamps on the carriage were lit.

“No matter,” he said. “The idea is the tale, my friend. You have your wonderful Sergeant Cuff. But even the best detective requires a mystery to solve if he is to be of any use or interest to your readers. That is what I hoped would come of our luncheon and Dradles outing today.”

“A mystery?” I said stupidly. “What mystery was there today?”

Dickens opened his hands and arms to take in the dark cathedral, the darker graveyard, and the many tombs and headstones. “Imagine a villain so devilish and clever, my dear Wilkie, that he murders someone simply to have had the experience of murder. Not murder a family member, as was the way of it in the Road Case in which you and I were both so interested—no, but to murder a stranger, or near-stranger. A murder with no motive whatsoever.”

“Why on earth would any human being do that?” I asked. Dickens was making no sense to me whatsoever.

“I just explained,” he said with perhaps some small exasperation. “To have the experience of having murdered someone. Imagine what a boon that would be to an author such as yourself—or to me. To any writer of imaginative prose, much less the sensationalist imaginative prose for which you are known, my dear Wilkie.”

“Are you talking about preparation for reading a Murder in your upcoming tour?” I asked.

“Good heavens, no. I have my poor Nancy waiting to be done in by that ultimate villain, Bill Sikes, someday. Not now. Already I have jotted down improvements on the method and description of that bloody massacre. I am talking about your tale, my friend.”

“But my tale is about a diamond that brings bad luck to the family that…”

“Oh, bother the diamond!” cried Dickens. “That was just an early draft of an idea. The Koh-i-noor diamond was a disappointment to everyone who went out of their way to see it at the Great Exhibition. Its color was a sickly, urine yellow—no real diamond to the English eye. Toss away your worthless gem, Wilkie, and follow the path of this new tale!”

“What tale?”

Dickens sighed. He ticked off the elements on the fingers of his gloved hand. “Element the first—the idea of someone murdering a near-stranger simply for the experience of having murdered. Element the second—the perfect way to dispose of a body. Your Sergeant Cuff will have a devil of a time figuring that out!”