Please note:
I should forewarn, this is where it heads a little bit AU/non-canon with regards to Sherlock's past history with Jim Moriarty
Hope that isn't a problem.
FIFTEEN YEARS EARLIER
The door to the library creaked open, alerting Sherlock that he was no longer alone.
He raised his eyes from the book he was reading but saw no one.
From his corner of the aisle end in the library, he couldn't see the door anyway so he supposed that whoever had come in would also be unable to see him.
He hoped they would just get what they wanted and leave quickly and quietly however he soon realised that this wouldn't be the case.
"Did you get it?" a hushed, nervous-sounding voice asked.
There were shuffling noises and the sound of two chairs moving, as people seated themselves, echoed conspicuously through the large expanse of the library.
Two people then, Sherlock realised with an eye roll.
"Of course, Sebby." a reply came. The soft, Irish lilt sounded completely calm and in control, in contrast to the evident nerves of the first speaker.
"You have the money?" the Irishman continued.
Sherlock frowned. What were these people doing?
He had expected them to be late-comers looking for study aids but clearly whatever was going on was much more underhanded.
He slid his chair out quietly and sneaked to the end of the aisle. He could just make out the shapes of the two men, seated in a corner, out of view of the main door.
Students? he wondered. Impossible to tell from here, but he couldn't risk getting closer. Not without being seen.
Irish guy carried on talking; "It's fifty for the coke and forty-five for the charlie. And this isn't your ordinary street shit that you're getting here. This is proper high-grade stuff. Use it carefully."
The first guy - Sebby? - grunted an acknowledgement and stood, fumbling as he rummaged in his coat pockets and counted out cash.
Clearly this guy was nervous. An amateur, Sherlock supposed. First-timer, perhaps. Or whatever those new to buying drugs were called.
Irish guy nodded to Sebby, taking the money and handing over two small packets. Sebby grabbed the packs, nervously stuffing them into his jacket and turning to leave.
As the door clicked closed behind him, Sherlock realised that the Irish guy hadn't left; hadn't moved, in fact.
He was still sat at the table, his back to Sherlock, doing something which Sherlock couldn't see.
"See anything you like?" the Irish voice floated across the library, startling Sherlock from his position in the aisle where he had been standing quiet and, he thought, unnoticed.
"Don't be shy." it continued, "we're all friends here." The Irishman stood and turned towards where Sherlock had been hiding. Sherlock, realising the futility of attempting to remain hidden at this point, stepped out from the aisle and into the main room, facing the Irishman who had now approached to within three feet.
Sherlock may have looked confident however he far from felt it, and he really was not sure what to say to the person who he just seen dealing drugs on campus.
As it turned out, he didn't need to say anything.
"Ahhh, the elusive Sherlock Holmes!" the Irishman took another step forwards, taking the stunned Sherlock's hand and shaking it firmly.
"I have heard so much about you. Jim Moriarty." he offered. "It is my pleasure to finally make your acquaintance."
Sherlock raked his eyes over the Irishman, taking in his confident, well-dressed manner. He was truly stunning to look at.
Realising that he hadn't responded, Sherlock collected his thoughts and pulled himself together.
"Indeed." he finally replied. "I fear my reputation precedes me?"
Jim Moriarty threw his head back and laughed.
"Quite. But don't let this little event bother you." he waved his arm about the library, referring to the dealings which Sherlock had so obviously been witness to. "This is purely business. You however... you are most definitely a pleasure." The Irish lilt purred out the word 'pleasure' and Sherlock felt Jim grab his hand more firmly.
"Come." he instructed. "I have something to show you."
Sherlock had no idea why he was following a drug dealer through the campus buildings. All he knew was that this man; this crazy Irishman; Jim Moriarty intrigued him. Aside from noting that he was well-educated, well-spoken and well-dressed, he had not managed to deduce much about the young man. He was a mystery and Sherlock Holmes loved a mystery.
Jim finally stopped at a large dark oak door, unlocking it swiftly and signally for Sherlock to enter with him.
Sherlock stepped into what appeared to be a self-contained apartment, decorated lavishly with dark red velvet drapes and furnishings with purple accents.
He crossed to an ornate candle stand, which appeared to be positioned prominently in the room, and examined it studiously.
"Beautiful, isn't it?" Jim whispered from almost right behind Sherlock. "The antique silver finish is a perfect contrast to the rich deep purple candles, don't you think, Sherlock?"
The Irishman gazed at Sherlock who was looking rather bemused at the arrangement. Jim hummed to himself quietly before suddenly asking,
"Tea?"
Sherlock blinked twice, processing the change of ambience in the room which had gone from intense to tea in under a second.
"Um, right. Yes, please." he responded. "Thank you."
A few minutes later, both men were sitting in opposite wing back chairs, cradling cups of tea.
"My father told me all about you, you know, Sherlock." the Irishman began. "The child genius, he called you. 'You must seek him out', he used to tell me. 'He's so like you, Jim', he would say. 'You must make friends' " Jim chuckled.
Like me, Jim scoffed to himself. As if this confused, awkward, naive 'boy' could ever be anything like me.
Sherlock hesitated, not entirely sure how to respond to Jim's account.
"Right," he started eventually, "Well, I don't really have 'friends'." Sherlock took a calming drink of his tea before continuing.
"People tend to see me as something of a... " he paused, looking at Jim who appeared to be hanging on his every word, watching intently over his tea cup " ... a freak."
"My mind", he continued, "is always active. Always busy. Working; analysing; deducing. It overwhelms people, I suppose. They seem to dislike it." he tailed off, hoping he didn't sound as stupid as he felt.
Jim nodded. He knew. He understood.
"Sherlock." he began quietly, his Irish tone soothing and melodic, "I have just the thing for you."