“You mean the Falls of Reichenbach ?” Mycroft looked shocked. “My God, yes, but I should think that’s the last thing you’d want to relive.”

“Aptly said!” declared Holmes. “Can you do it?”

“Of course.”

“Then do so!”

And so Holmes and my brains were scanned and in short order we found ourselves inside a superlative recreation of the Switzerland of May, 1891, to which we had originally fled to escape Professor Moriarty’s assassins. Our re-enactment of events began at the charming Englischer Hof in the village of Meiringen. Just as the original innkeeper had done all those years ago, the reconstruction of him exacted a promise from us that we would not miss the spectacle of the falls of Reichenbach. Holmes and I set out for the Falls, him walking with the aid of an Alpine stock. Mycroft, I was given to understand, was somehow observing all this from afar.

“I do not like this,” I said to my companion. “’Twas bad enough to live through this horrible day once, but I had hoped I would never have to relive it again except in nightmares.”

“Watson, recall that I have fonder memories of all this. Vanquishing Moriarty was the high point of my career. I said to you then, and say again now, that putting an end to the very Napoleon of crime would easily be worth the price of my own life.”

There was a little dirt path cut out of the vegetation running halfway round the falls so as to afford a complete view of the spectacle. The icy green water, fed by the melting snows, flowed with phenomenal rapidity and violence, then plunged into a great, bottomless chasm of rock black as the darkest night. Spray shot up in vast gouts, and the shriek made by the plunging water was almost like a human cry.

We stood for a moment looking down at the waterfall, Holmes’s face in its most contemplative repose. He then pointed further ahead along the dirt path. “Note, dear Watson,” he said, shouting to be heard above the torrent, “that the dirt path comes to an end against a rock wall there.” I nodded. He turned in the other direction. “And see that backtracking out the way we came is the only way to leave alive: there is but one exit, and it is coincident with the single entrance.”

Again I nodded. But, just as had happened the first time we had been at this fateful spot, a Swiss boy came running along the path, carrying in his hand a letter addressed to me which bore the mark of the Englischer Hof. I knew what the note said, of course: that an Englishwoman, staying at that inn, had been overtaken by a hemorrhage. She had but a few hours to live, but doubtless would take great comfort in being ministered to by an English doctor, and would I come at once?

“But the note is a pretext,” said I, turning to Holmes. “Granted, I was fooled originally by it, but, as you later admitted in that letter you left for me, you had suspected all along that it was a sham on the part of Moriarty.” Throughout this commentary, the Swiss boy stood frozen, immobile, as if somehow Mycroft, overseeing all this, had locked the boy in time so that Holmes and I might consult. “I will not leave you again, Holmes, to plunge to your death.”

Holmes raised a hand. “Watson, as always, your sentiments are laudable, but recall that this is a mere simulation. You will be of material assistance to me if you do exactly as you did before. There is no need, though, for you to undertake the entire arduous hike to the Englischer Hof and back. Instead, simply head back to the point at which you pass the figure in black, wait an additional quarter of an hour, then return to here.”

“Thank you for simplifying it,” said I. “I am eight years older than I was then; a three-hour round trip would take a goodly bit out of me today.”

“Indeed,” said Holmes. “All of us may have outlived our most useful days. Now, please, do as I ask.”

“I will, of course,” said I, “but I freely confess that I do not understand what this is all about. You were engaged by this twenty-first-century Mycroft to explore a problem in natural philosophy — the missing aliens. Why are we even here?”

“We are here,” said Holmes, “because I have solved that problem! Trust me, Watson. Trust me, and play out the scenario again of that portentous day of May 4th, 1891.”

And so I left my companion, not knowing what he had in mind. As I made my way back to the Englischer Hof, I passed a man going hurriedly the other way. The first time I had lived through these terrible events I did not know him, but this time I recognized him for Professor Moriarty: tall, clad all in black, his forehead bulging out, his lean form outlined sharply against the green backdrop of the vegetation. I let the simulation pass, waited fifteen minutes as Holmes had asked, then returned to the falls.

Upon my arrival, I saw Holmes’s Alpine stock leaning against a rock. The black soil of the path to the torrent was constantly re-moistened by the spray from the roiling falls. In the soil I could see two sets of footprints leading down the path to the cascade, and none returning. It was precisely the same terrible sight that greeted me all those years ago.

“Welcome back, Watson!”

I wheeled around. Holmes stood leaning against a tree, grinning widely.

“Holmes!” I exclaimed. “How did you manage to get away from the falls without leaving footprints?”

“Recall, my dear Watson, that except for the flesh-and-blood you and me, all this is but a simulation. I simply asked Mycroft to prevent my feet from leaving tracks.” He demonstrated this by walking back and forth. No impression was left by his shoes, and no vegetation was trampled down by his passage. “And, of course, I asked him to freeze Moriarty, as earlier he had frozen the Swiss lad, before he and I could become locked in mortal combat.”

“Fascinating,” said I.

“Indeed. Now, consider the spectacle before you. What do you see?”

“Just what I saw that horrid day on which I had thought you had died: two sets of tracks leading to the falls, and none returning.”

Holmes’s crow of “Precisely!” rivaled the roar of the falls. “One set of tracks you knew to be my own, and the others you took to be that of the black-clad Englishman — the very Napoleon of crime!”

“Yes.”

“Having seen these two sets approaching the falls, and none returning, you then rushed to the very brink of the falls and found — what?”

“Signs of a struggle at the lip of the precipice leading to the great torrent itself.”

“And what did you conclude from this?”

“That you and Moriarty had plunged to your deaths, locked in mortal combat.”

“Exactly so, Watson! The very same conclusion I myself would have drawn based on those observations!”

“Thankfully, though, I turned out to be incorrect.”

“Did you, now?”

“Why, yes. Your presence here attests to that.”

“Perhaps,” said Holmes. “But I think otherwise. Consider, Watson! You were on the scene, you saw what happened, and for three years — three years, man! — you believed me to be dead. We had been friends and colleagues for a decade at that point. Would the Holmes you knew have let you mourn him for so long without getting word to you? Surely you must know that I trust you at least as much as I do my brother Mycroft, whom I later told you was the only one I had made had privy to the secret that I still lived.”

“Well,” I said, “since you bring it up, I was slightly hurt by that. But you explained your reasons to me when you returned.”

“It is a comfort to me, Watson, that your ill-feelings were assuaged. But I wonder, perchance, if it was more you than I who assuaged them.”

“Eh?”

“You had seen clear evidence of my death, and had faithfully if floridly recorded the same in the chronicle you so appropriately dubbed `The Final Problem.’”

“Yes, indeed. Those were the hardest words I had ever written.”

“And what was the reaction of your readers once this account was published in the Strand ?”