Gregory Lestrade had first met Sherlock a long time ago, not long before he became a Detective Inspector, and a long time before Sherlock was clean, let alone presentable to the rest of society. Anderson was working somewhere in Manchester and Donovan hadn't even finished her training.
At first he hadn't particularly liked the younger man (or even at all), never mind wanted to let him on his crime scenes. The drugs had made the boy's (he looked barely older than nineteen or twenty) tongue sharper than usual, not that he'd known that at the time. All he'd seen was a particularly rude stalker who knew far too much of his private life.
The day they'd met hadn't been particularly complicated – or so he'd thought at first. The weather had been difficult, fluctuating between pleasant and awful; which really should've been an indicator as to the kind of day that was to follow.
The case had been fairly simple as well. A shoe fetish, a murder and they'd arrested the main suspect and were hoping to be back at the Yard in time for lunch.
As they were packing up and leaving, Lestrade had spotted a teenager with glazed but intense eyes and a short sleeved black t-shirt that explained everything. The boy's hair was matted and wild, despite the current outburst of rain, and he was paler than anyone Greg had ever seen.
When the boy had first spoken his voice had been sharp but eloquent, in spite of his grubby appearance and combined with what he was saying Greg had been convinced someone else was speaking. "You've got the wrong person you know."
No, the boy was the only other person around – the others had headed back to the Yard and the forensics team was sniffing around the crime scene. "What?"
The boy seemed amused. "You've arrested the wrong man."
Greg humoured him. "Have we?"
A slight smirk appeared – one he would learn to loathe – and a sliver of intelligence, brilliance, sparked through the clouded eyes. "You'll see. Soon."
"And why do you think that?"
"Why do I think you've got the wrong man or why do I know you'll find that out soon? You should be more careful with your questions Sergeant Lestrade."
Lestrade started. "How do you know my name?"
The boy ignored the question. "Take a look at the victim's passport and then back at his phone." And then, without looking back, the boy turned on the spot and disappeared into the shadows. Lestrade stared incredulously after him before sighing. It had seemed too good to be true and it couldn't hurt to double check.
He just wouldn't be telling his superior's he was taking policing advice from random junkies off the street. Or he'd never get that promotion.
oOo
The second time Lestrade met Sherlock; it was during a drug's bust. It wasn't a first for either of them but it was the first of many involving the two. This one, however, definitely involved actual drugs.
(As Lestrade later told Sherlock, it was quite good they'd turned up when they had. Sherlock, not that he'd know the boy's name yet, had merely scowled and said 'he' wouldn't allow him to die. Lestrade hadn't known at the time who this 'he' Sherlock was talking about was. Now, Greg could make a fairly reliable guess.)
When Sherlock was released from the hospital Greg couldn't decide whether he was glad to see him go or if he was going to miss the kid. But he knew the hospital staff wasn't going to miss him. Sherlock had been trying to leave for the last week and a half. An hour after his first escape attempt a small army of men in black suits descended upon the hospital and promptly deposited him back on his bed whenever he left it.
oOo
The third time they'd met hadn't even been his choice – or Sherlock's as he'd later heard. The current case was becoming increasingly complicated due to an apparent lack of links between victims.
Sherlock turned up at the crime scene and promptly solved the crime, finding a link between the victim's coats and watches, explaining it in that particularly annoying way that made you feel like an idiot for not seeing it before. Lestrade hadn't appreciated the feeling. Usually he was the one making people feel like the idiot. It hadn't happened to him since he'd become Sergeant.
He'd left the crime scene hoping to never see the arrogant man ever again.
He returned to the Yard to find an official order from the higher up's consenting to the use of Sherlock Holmes in solving crimes. Luckily he'd known the boy's name by now or else it would have confused him for a brief moment – who would let a druggie on a crime scene?
(Again, at the time he'd failed to work out how he'd received the order. What kind of police force allowed a drug addict to work with their officers to solve crimes? Now he made an educated guess.)
He agreed as long as Sherlock turned up to his crime scenes clean.
(He didn't admit it but the younger man was starting to grow on him. Sherlock could tell anyway.)