Harold stood in the spot where Conan Doyle’s desk had been. Where his chair had been set back. Where the stories had been composed, where they had been written down in longhand. Where Sherlock Holmes was resurrected.

The old centuries had, and have, powers of their own, which mere modernity cannot kill. Stoker had been right. So had Alex Cale. There was something alive in this house. Not even modernity, not even the horrible rinse of history, could kill what had been born here.

Harold formed his hand around an imaginary pen. He placed it on his imaginary paper, on top of his imaginary desk. He wrote, imaginarily, with a wide flourish.

Penelope Higgins coughed. She seemed used to this sort of behavior from visiting Sherlockians.

“What are you looking for, Mr. White?” Her tone was firm. She wanted a real answer.

“The diary,” said Harold, absentmindedly. “I’m looking for the diary.”

Ms. Higgins smiled. “Best of luck to you, then,” she responded. “You’ve an illustrious set you’re following. Since 1930 we’ve had chaps like yourself in and out of this room looking for that diary. How many times do you think they’ve paced around here? How many times do you think they’ve pulled at the floorboards? Tapped at the walls for hollow spaces? Unscrewed the light fixtures? They must have gone over this room…what, now? A hundred times? A thousand? That’s more than eighty years of Sherlockians that’ve been in here. I don’t think there’s much left for you to search.”

Now it was Harold’s turn to smile. And he smiled bigger and wider than Penelope Higgins ever would. Here he was in Conan Doyle’s own study, in his own house, and here before him was a mystery worthy of his efforts.

“Elementary,” Harold said, because he simply could not resist.

Penelope Higgins shook her head.

“I’ll leave you to it, then. Here are the photos. Just don’t poke yourself on a rusty nail, give yourself tetanus.”

Penelope Higgins left, though she did not close the door. It seemed she would wearily give Harold the benefit of the doubt.

He settled in. He sat on the broken floor. He closed his eyes. He pressed his stubby fingers together in his lap, and he devoted his mind to the task at hand.

The diary would not be found by searching. It would be found by thinking. All problems have solutions, even if they’ve evaded a generation of inquisitors.

The diary was here. It had been hidden here a hundred years before. But how? But where? He had no doubt that scores of Sherlockians, of scholars both professional and amateur, had combed over every inch of this room. What would they have missed? What hiding place was obvious enough that Bram Stoker was able to quickly stash a leatherbound book in it, without plan or preparation, and yet was ingenious enough that both Conan Doyle and a thousand literary detectives had missed it? What spot had remained untouched over a century of icy winters, summer storms, and ravaging descendants?

Harold thought of “The Purloined Letter.” No. In this case, the diary had not been hidden in plain sight. That would be too easy.

What was the twist? If Conan Doyle had hidden the diary himself, where would he have hidden it? Or, better yet, if Conan Doyle had hidden the diary for Holmes to find and Holmes were strolling through this study right now, where would he look? If Harold was sure that the diary was hidden here, and he was… well then, he was only more sure of one thing: that there would be a twist. Because there always was.

He thought of all the great twists he’d read at the ends of all the great mystery novels. Some were small shifts of focus, others were radical shifts of plot, such that everything you thought you knew turned out to be false. Harold wasn’t certain what sort of twist he hoped for. But all the best twists he’d read shared one key feature.

The well-written twist always preyed upon the reader’s assumptions. Something the reader had simply assumed to be true-because how could it not be?-turned out to be false. Something unquestioned was questioned. Something that had never felt worth examining was examined, and an answer was found in the most unlikely place.

What did Harold assume? That Bram Stoker had hidden the diary so that he could come back later and destroy it. That Bram Stoker had hidden the diary within this room. That no one had ever found it. That the room had been emptied, destroyed, turned over a thousand times and that the diary wasn’t here.

That the diary had been here. That the diary wasn’t here.

Harold stopped breathing.

The diary had been here. The diary wasn’t here.

And it was all so stunningly, embarrassingly obvious.

He flipped through the pages of photographs quickly, looking hard at the gray-on-gray images.

“Have we found the diary yet?” came the voice of Penelope Higgins.

He looked up to find her stocky frame in the doorway.

“Yes,” said Harold, in no mood for games.

Ms. Higgins laughed at him through her nose. “Right then! Well, where is it?”

Harold earnestly turned back to the photos, plowing through her sarcasm. “The diary was hidden here in 1900. But it’s not here anymore, and it wasn’t here after Conan Doyle died. So at some point between 1900 and 1930, someone took it out of this room.”

“So somebody stole it?”

“No. Somebody took it out of this room. But I don’t think they knew what they were taking. I think somebody removed the diary by accident, not realizing what it was. So what I want to know now is, what was taken out of here in those years? What was big enough, and obvious enough, and hollow enough, that somebody could have quickly shoved a diary in it but that no one would have looked inside? It’s not a vase, it’s not a chest… Maybe the empty base of a lamp?”

“The lamps all went to Conan Doyle’s daughter, I believe. And there weren’t many of them. Fairly little, too, if I remember. Probably kept them in her attic. But I don’t think you’d be the first to search Conan Doyle’s daughter’s attic for the diary, Mr. White.”

Harold turned the page and laid his eyes on a small, dark photograph from 1899. It was of the study, of a liquor table in one corner, festooned with clear decanters and a strange, tall object. He squinted and looked closer. It was bigger than any of the liter-size decanters, wider around the bottom and rising a good two feet into the air. Both the base and the balloon-shaped body were made of opaque glass. A series of what looked like tubes ran around it, and something like a nozzle poked out from the top.

He flipped the pages quickly, finding a later photograph of the same space. It had been taken in 1905. The angle was different, and the liquor cabinet was in a slightly farther spot along the wall… But the object was gone. In its place was something similar but smaller. Much smaller.

He pressed his finger against the first photograph. “What is this?” he asked. “It’s hard to make out.”

Penelope Higgins bent over the photograph book herself, squinting past her thick, round glasses.

“Oh!” she exclaimed. “The gasogene!” Harold remembered reading about gasogenes over the years, but he didn’t think he’d ever seen one. They were early carbonators, used privately to put the bubbles in a gentleman’s seltzer. They were expensive and rather unwieldy, and they were found only among the bar sets of the wealthy.

“It’s huge,” said Harold.

“Yes, rather. It was an early gasogene, I think. Conan Doyle received one of those monstrous nineteenth-century ones early on and got rid of it when the newer ones were developed a few years later. This one was a gift, if I recall.”

“From who?”

“Bram Stoker. They were friends, you know.”

Harold froze again.

“He got rid of it? To where?”

“Hell if I know,” said Ms. Higgins. “Conan Doyle would have sent the thing away long before he died. 1901? ’02? ’03? Must have been.”