Excitedly, Sherlock started to read a passage from the book in front of him.

Despite his background in medical science John was beginning to feel lost within the first ten minutes, what with whole physics of matter and energy overlaid with metaphysical philosophy but still his friend, heedless, continued reading various passages.

As he moved on to another book John stepped closer.

"Wait." He said, finally catching up with Sherlock's thousand-words-per-second explanation. "Hang on Sherlock – are you telling me that we are just energy, caught in some kind of loop between the physical state of matter and the metaphysical possibilities?"

"Yes – didn't you hear what I was saying?"

John laughed.

"Sherlock that is the crankiest theory I've ever heard you come up with!" He gestured towards the book that he had been reading earlier. "You're even beginning to sound like one of the witnesses in this book..."

Sherlock read the title – The 1894 Census of Hallucinations – and frowned at his friend.

"...it's just a collection of so-called ghost sightings, and theories as to why they happened, there's everything there from sad ghosts who don't want to leave their loved ones, to angry ghosts who want revenge on their murderers and every other type of ghost in between!"

"But John, don't you see? This is partly a particle physics theory, the question around is matter real? And whether or not reality can be explained in terms of matter and energy."

"Still doesn't explain why we're here. Let's face it, everything we read will simply tell us the living theories of ghosts – no one has as yet written it from the ghost's point of view."

Opening his mouth to refute John's comments Sherlock suddenly looked stunned.

"You're right." He said finally. Pacing away, he looked distressed. "There has to be an answer."

"Why?"

"What do you mean why?"

"Tell me, if you were to look at the phenomenon logically, what would your logical brain tell you about ghosts."

"That they can't possibly exist, but John..."

"So logically neither you nor I can actually be here?"

"Yes... I mean no..."

"Y'know Sherlock, I really wish I could appreciate you being this lost for an answer, but in all honesty I can't." He sighed gustily and ran a hand over his face. "I know the scientist in you wants to pin this down, but I'm afraid you aren't likely to do it."

For a moment Sherlock just stared at him, his face a curious mixture of annoyance and resignation.

"I don't like not knowing John, and I especially don't like it when it's my own existence that I cannot explain."

The vulnerability in his voice tugged at something inside John. Sherlock had always been so sure of himself and his ability to solve any problem that it hurt to see him so lost.

His feelings must have shown on his face because a moment later Sherlock was once more his usual acerbic self.

"Stop pitying me John – you're in the same predicament that I am."

"Yeah, but I at least am content to accept the fact that what is just is, and if it can't be explained at least I won't worry about it."

"I envy you."

Surprisingly, Sherlock genuinely meant it, and it just made John want to reach for something to keep him occupied for the last hour before midnight, something that would at least take his mind away from the lack of answers.

The CCTV camera caught his eye, and he huffed a short laugh.

"Looks like the security equipment in here is almost as ancient as the books it's guarding."

Sherlock followed his line of sight.

"I don't think I've seen cameras like this since I was in school." John added as they both moved to stand in front of the lens. "I wonder if we can be seen on this like we can the modern ones?"

"These operate on a tape feed rather than a digital recording." Sherlock supplied, his mind doing what it did best and throwing facts out for him to impress his friend. "Generally they work on a twenty four hour loop."

"Does that mean more likely or less likely then?"

"Let's find out." Sherlock replied with a slight smile. "This time I'll concentrate and you can pass a message to... Who are we going to leave a message for?"

"Greg would be the obvious one – the police will get involved if they see us on the tapes, and the minute he hears about it Greg will want to see for himself anyway, so why not direct it straight to him?"

"Right." Sherlock turned to face the camera full on before adding "Just try not to make it too sentimental."

xXx

Greg Lestrade walked into the New Scotland Yard building feeling refreshed and ready to face whatever the day has to throw at him. In fact, he could get used to dining in the Diogenes Club, and it appeared that Mycroft Holmes was equally as happy to make this an annual event in honour of his brother and John Watson.

It still seemed strange, not to have those two lunatics bursting into his office at the most inappropriate times to tell him how to do his job, and he was surprised to find himself admitting to the elder Holmes that he actually missed the insults and snarky remarks.

Mycroft had understood exactly what he meant – of course he would, this was his brother they were talking about – and as they sat once more exchanging reminiscences about Sherlock and John he had felt strangely accepting of the fact that now this was how it would be – memories and nothing more...

Pointedly neither he nor Mycroft had mentioned last year's strange goings on, although he wondered if like himself, the other man was expecting some sort of visitation. He shook off the daft daydreaming as he exited the lift and crossed to his office.

"Sir, there was a message for you." Sally Donovan intercepted him as he was about to walk through the steel and glass door.

He pulled out his mobile and glanced at it.

"No, they said it wasn't urgent, but to tell you when you came in." She looked at him a little strangely.

Greg carried on into his office, knowing that his DS would follow. She closed the door and waited until he had hung up his overcoat.

"It was the security guys from the British Library. They said that something strange had happened there last night."

A cold sense of déjà vu ran fingers down Greg's spine.

"Why tell me?"

"It seems that there was a message left there for you."

He stared at her, frowning.

"Did they say what kind of message?"

"They said you'd want to see it for yourself."

For several long minutes Greg just stood staring at his desk, then he nodded.

"British Library you say? Okay, if they ring again tell them I'll be on my way in a short while."

"I'll get the car..."

"No it's okay Sally, I need to make a call then I'll buzz over there – no need for us both to go."

He could see the disappointment in Sally's face, but she had no reasonable argument to make in favour of her going with him. She nodded and backed out of the office.

Once the door was shut behind her, Greg picked up his mobile and pressed the speed dial.

"Mycroft Holmes residence." An elderly male voice at the other end said.

"I need to speak to Mr Holmes urgently." Greg responded. "My name is Detective Inspector Greg Lestrade – he will know who I am."

"Please hold sir."

A moment later Mycroft's rounded Eton tones came through.

"Gregory, what can I do for you?"

"Can you meet me at the British Library? Say in about thirty minutes?"

There was a slight pause, then

"I believe I told you last year that I'm not my brother, I don't 'do' crimes scenes."

Greg stifled a laugh.

"No, but you do 'do' strange messages at Halloween..."

"I beg your pardon?"

"Yeah. Apparently something odd happened at the library last night, and a message was left for me – now if it was a break in or something even vaguely resembling a crime scene it would have come through normal channels."

"Let me pick you up and we'll go together."

xXx

Walking side by side through to the security office, Greg and Mycroft kept silent. In the car they had returned to the previous year's message, yet neither ventured a suggestion as to what had caused this particular event.

At last they were shown into an airy room with a dozen or more monitors around the walls.

"If you come through to the manager's room," the officer said "I can show you what we found."

He waited until they were seated then switched on a largish monitor.

"Every morning we run through the tapes just to make sure nothing untoward has happened overnight, and Sunday's are no different – well, at least they weren't."

Mycroft cocked an elegant eyebrow. Greg waited patiently.

"Well then, we were looking through the tapes when suddenly we saw this..."

And on the screen appeared two figures, Sherlock Holmes and John Watson, much the same as the previous year except that this time it was John doing the talking...

'If you can see and hear us, this is a message for Detective Inspector Greg Lestrade. You can reach him at New Scotland Yard, the number's in the book...'

'John stop wasting time...'

'Yeah right. Anyway Greg, if you can see and hear us you are officially part of one of Sherlock's wonderful experiments! The equipment in this room is so old it has 'Property of Noah' stamped on it'

Greg barked out a sharp laugh.

'We wanted to know if equipment this antiquated is as sensitive as the new digital stuff. So it's going to take us a year – won't feel like that to us but there you go – to get an answer on this but if you see us, can you leave a message somehow? Probably leave it back at home somewhere, because that's where we always seem to start out.'

The figure glanced over his shoulder, looking pointedly first at the clock with read 11.55, then at his friend, and then turned back to the camera to add with a grin

'And for God's sake Greg, try to arrange a nice murder for him for next Halloween – he's driving me demented!'

As they watched the two friends, still laughing at the screen, started to fade from view.

The security officer stopped the recording and looked at Greg and Mycroft who were, it had to be said, taking it all very calmly.

"Can you show us the room that this feed came through from?" Greg asked, but to his amazement the guard shook his head.

"Look at that room." He said pointing to the now frozen image on the screen. The barest outline of the fading apparitions frozen too, but through them could be seen the old room, the dusty shelves and the ancient books. "That room was pulled down to make way for this building back in the early nineties. That's why the cameras and stuff looked old to them."

"But..."

"The room was always said to be haunted, that was why they put the books about paranormal and supernatural phenomena in there." The security officer scratched his head, and then grinned. "Looks like they were onto something!"

A/N: That's it friends...until next Halloween...