Usual disclaimer: Holmes and Watson are the creation of Sir Arthur Conan Doyle and do not belong to me.

BY THE PRICKING OF MY THUMBS

"Don't go up into that tower tonight, gents – Sir Lucas walks abroad on nights like this, so he does."

I recalled the housekeeper's words more than once as I followed Holmes through the deserted tower that evening. He, naturally, had ignored the good woman's warning, probably not even aware of the date, but I am afraid to say that my nerves on this occasion failed to match my friend's, and the implications of our situation were very real to me.

This was in part due to the lonely, isolated and abandoned nature of the building in which we presently found ourselves. The tower was at the very edge of the east wing of the house, and had not been occupied for three centuries; shut up by the family after one of their number – Sir Lucas Trent – committed suicide in spectacular fashion by throwing himself from the very top of the turret before the horrified eyes of his children after being spurned by his beautiful young wife.

I will say now that I am not naturally a nervous man, and dangerous situations hold no fear for me. I have been a soldier, and over a decade's acquaintance with Sherlock Holmes has accustomed me to all kinds of peril. However, the dark, echoing chambers and the curtain of cobwebs which greeted us as we opened the rusty door did not in my opinion bode well. It would have been uncomfortable at any time, walking into such an unloved and unhappy environment, but on All Hallow's Eve it was particularly difficult.

Holmes, naturally, thought nothing of this, taking no notice of the ominous creak made by the door as he swung it back and lifting his lantern high to guide us into what had once been Sir Lucas's inner sanctum. Though I knew that the door had creaked because its hinges had not been oiled since the late sixteen hundreds, I could not help the shiver that ran straight down my spine upon hearing it. I remained outside, some unknown force preventing me from crossing the threshold, until at last Holmes, having realised I was not behind him, turned back, the lamplight casting strange shadows from his hawkish features and turning his face into a yellow carnival mask.

"Is something wrong, Watson?" he asked, spotting me hovering in the passage.

I could not explain my sudden reluctance to enter the tower any more than I could justify the superstition that had taken hold of me since the housekeeper had issued her warning. Until that moment I would have told anyone who might have asked that I did not believe in the supernatural, but now…now I was not so sure, and said so.

Holmes clucked his tongue impatiently. "We have a duty to the living to discover who is behind these thefts. This agency is firmly rooted in the here and now – no ghosts need apply," he said. "Are you coming, or shall I seek the culprit alone?"

With a sigh and deep breath, I marshalled my courage and stepped into the tower. The moment I did, I felt my skin rise in gooseflesh, as though I had stepped into a draught. I glanced about me, but the cobwebs were still – there was not a breath of air in the room. Holmes had taken the lamp and was prowling the perimeter of the chamber, brushing the thick white webs aside. The work of many generations of spiders, they had the appearance of gossamer drapes, bestowing upon the room an ethereal air. I walked hesitantly through them, feeling them catch upon my shoulders and in my hair, my footsteps on the rotting floorboards muffled by the thick layer of dust.

No one had entered this room since the day Sir Lucas died. Paintings hung on the walls, blackened by age; his papers still lay upon the desk, the quill brittle and stained with ancient ink. On the high back of the Carolean chair hung a gentleman's coat of what must once have been fine plum velvet, abandoned there by the man who had hurled himself to his death from the roof above us, driven to despair by the woman he loved. Reaching out, I dared to touch the fabric, only to have it crumble under my fingers, dust in mere moments.

"He has done it very well," muttered Holmes. "I congratulate him."

"Who has?" I asked, still in the dark as to the identity of the thief.

"Baxter. He has thought of everything. A very nice little hiding place this has turned out to be."

I glanced around me. Apart from our own there were no prints in the dust, no evidence to suggest that anyone had been here before us. "You think he has been operating from here?"

"Of course." Holmes looked at me as if the solution were obvious. No doubt it was to him, with all of the facts in his possession. "The legend of Sir Lucas has been the perfect protection."

"But, Holmes, no one had opened that door for three hundred years until you turned the key. How has Baxter been gaining entrance to the tower?"

"There are plenty of windows, Watson. If a man desires entry he will find a way, and the roof is accessible from the main house. I saw a figure on the turret last night – it must have been our quarry."

"It might have been Sir Lucas," I pointed out. "It is after all - "

He gave me a withering glance. "The date means nothing, Watson. I have no truck with superstition – just because the calendar states it, the dead do not rise up at an appointed hour to haunt the living. I am sure they have far better things to do."

"Mrs Henty told us that Sir Lucas always walks abroad on the thirty-first of October. He has been seen many times."

"ʻBy the pricking of my thumbs, something wicked this way comes'? Oh, Watson, you surely do not believe the tales of an old woman? No doubt she has been trotting out the same story to visitors for the past forty years. If everyone believed in such nonsense, we would - " Holmes stopped speaking abruptly as the lamp in his hand quite suddenly went out, pitching us into darkness.

My heart leapt into my throat. "You should not be so dismissive," I said in a rather strangled voice.

"It was merely a gust of wind," he said firmly.

"There is no air in here, Holmes."

"There must be a broken window, a draught from under a door. That is the only explanation," he insisted.

The gooseflesh on my arms had returned; I could feel it despite the heavy fabric of my jacket. Icy fingers inched their way down my back. Though we stood in pitch darkness, I was sure that someone was watching me. Before I could speak of it to Holmes, my ears caught the sound of music, very faint and only just on the edge of my hearing. It was strange and ancient-sounding, the notes sharp and disjointed. I did not recognise the tune, but it was eerie, melancholy.

My throat was dry as I whispered, "Holmes, can you…"

There was a pause. I distinctly heard him swallow before he said, just as softly, "Yes, I hear it."

"Do you think it might be Lady Isabel, in the music room?"

Another pause. Holmes's voice contained the slightest tremor as he replied, "The music room is on the other side of the house, and I do not think the family own a spinet."

"Then…?"

"I…rather think that in my researches I came across a mention of Sir Lucas being proficient upon the instrument."

We stood in silence for some seconds, as the music, still only just audible, played on. My cold feeling increased tenfold, and was sure there were eyes upon me, despite the darkness. From the harsh breathing of my friend beside me, I knew that, whatever his inclinations, he could feel it too, however much he might try to explain it away. It took a great deal to rattle Holmes, but he was most definitely shaken now, I was sure of it.

"Can you light the lamp?" I asked, grasping his arm to make sure that it was indeed him at my side.

He was trembling, and not just from the cold. I heard a rustling noise as he put a hand into his pocket. He swore under his breath. "I do not seem to have my matches."

"But you used them to - "

"I know."

There was another pause. Quite irrationally I did not now want him to light the lamp, for I did not wish to see whatever, or whoever it was I felt lurking on the edges of my perception. And there was someone in the room with us, of that I was now quite certain, someone who had made no sound on the boards as they approached, and who would have left no footprints behind them. Holmes said nothing, and I knew that he was using all of his formidable intellect to find a prosaic and ordinary reason for what was happening.

At last I could stand the silence, broken only by the sound of our breathing, no more. "Holmes?" I hissed.

I heard him take a deep and slow breath. "I think that a tactical retreat might be in order. We are unarmed, and he has the advantage of us."

I gazed about me in the darkness but it was absolute – I had no idea in which direction the door lay. Beside me Holmes was rummaging in his pocket again, and he gave a little cry of triumph. There was the sharp scrape of a match, and a moment later he had coaxed the lamp into feeble life. He did not wait to look at our surroundings but made immediately for the door. I followed upon his heels, determined that he should not leave without me. As I crossed the threshold the hairs rose on the back of my neck as though a chill breeze had touched me, and I distinctly heard a deep, throaty laughter. The sound propelled me back into the main house – I fairly bolted into the passage, closing the door swiftly behind me and leaning upon it.

When I had recovered myself I looked up at Holmes. He was pale in the lamplight, but the unease I had felt and heard back in the tower was hidden behind the mask he habitually wore. This was not a surprise, as he would never show his dealings even to me, unless forced, but the very fact that he had been able to light the lamp puzzled me.

"I thought that you could not find your matches?" I asked him.

"I could not."

"But how - "

"They must have somehow slipped into the lining of my jacket."

I was not to be taken in by his theory this time. "That is a brand new jacket, Holmes - you have no holes in the pocket for the matchbox to fall into."

"It is the only possible explanation," he insisted. His eyes narrowed. "Baxter is certainly a bold and clever man. He has far more ingenuity than I had at first given him credit for. It will take no little cunning to run him to ground."

I stared at him in amazement. "Holmes, after all that we have just witnessed, surely you cannot still maintain that Baxter was behind it all! There was a presence in that room, and it was no mere man. No human being could have produced such a terrible effect!"

"There can have been nothing else behind it, so logically it must have been Baxter. Eliminate the impossible, Watson, remember."

"No." I shook my head, straightening. "I know that there was something else in the room with us. I don't know what, exactly, but it was most definitely not Baxter. You felt it yourself, don't deny it." I looked him straight in the eye. "You know as well as I do that he was there."

He met my gaze, and hesitated, just for a moment. I could see the tiny spark of uncertainty in his eyes, but it was gone in a flash, and the confidence returned. "Poppycock," he declared, and whirled on his heel, heading for the main body of the house and the warm comfort of the living, his tall, lean shadow thrown onto the wall ahead of him.

For a second longer I lingered by the tower door, but I could feel nothing now. We had left Sir Lucas to his midnight wanderings, and he had left us now that he would be undisturbed. I glanced at Holmes's silhouette, disappearing down the passage, and hurried to catch up, not wishing to be left alone in the dark in this part of the house, even if its tragic master was no longer at my elbow. Whether it was due to my own imagination, or the potent symbolism of that night I still do not know, but that he had been there I was in absolutely no doubt. I followed Holmes, leaving the doomed occupant of the tower to his restless existence.

My friend's voice drifted back to me, adamant as ever: "No ghosts…need apply…!"

There are more things in heaven and earth, Horatio…

FIN

Author's Note: As a sceptic with much in common with Holmes, I am the first person to deny the existence of ghosts. However, my sister, a friend and I did have a very uncomfortable experience last summer at Bolsover Castle in Derbyshire (not helped by the place being empty at the end of the day and some freaky audiovisual effects from English Heritage), and it is upon this that the fic was based.