Part 1:

Sherlock as a general rule was not especially worried when his Irregulars disappeared for certain lengths of time. Sometimes, after all, they were caught.

Occasionally this was by do-gooders who wanted nothing more than for the kids to be at school and being fed three square meals in a relatively non-hostile environment.

Other times, it was the police, as though the Irregulars were more than happy to keep Sherlock informed enough to prevent crimes and catch murderers, on the other hand, drug use, stealing and generally getting up to mischief of the vandalism or joy-riding varieties were common-enough pursuits that Sherlock did not even bother to discourage them from.

After all, he of all people understood boredom.

So when the boy that Sherlock knew as "Eggsy" disappeared for a few weeks, Sherlock was initially not especially bothered. He heard from one of the others that Eggsy had been "picked up by the coppers fer nickin' Rottweiler's car and takin' it joyridin'," and assumed that the obvious had occurred- that Eggsy was serving some time.

But then one of Eggsy's friends, Jamal, (Sherlock never deleted the Irregular's names because… because it would mean that they would feel slighted and would cease informing him, yes, that was it,) asked Sherlock if he had heard anything about what happened to Eggsy, and wondered if the detective couldn't look into the matter. "Because I heard from his Mum that he somehow got released by the fuzz, and then he went home, his bastard step-father and his gang tried to kill him, and then he scarpered with the help of some toff-sounding bloke and hasn't been seen since." Jamal had swallowed. "Whole story sounds mighty on the nose, if you ask me, 'specially if you believe the rumour that Dean's gang were searching for some posh suit who apparently beat the shit out of them for calling Eggsy a rent-boy."

Sherlock paused. That scenario sounded…

Intriguing.

(And quite possibly, not boding well for Eggsy's health.)

Either way, it was certainly something he felt he should look into.

"Watson!" he shouted when he returned to 221B, "I have a case!"

Watson, (dressed as sloppily as ever in one of those awful cardigans that he always seemed to acquire regardless of however many destructive experiments that Sherlock conducted on them in the name of taste science,) looked up from his newspaper, an excited glint already coming into his eyes.

(It was times like this that Sherlock was reminded why it was that he was so fortunate to have his… blogger.)

Eight days later, and Sherlock was almost (almost, not quite, things had not quite reached that dire point) ready to call Mycroft in sheer frustration.

"Still haven't found your chav?" Sally Donovan asked them, unable to hide the slight sneer in her voice when she came to (grudgingly as ever) demand their help on the latest murder.

Sherlock sneered right back. "Gary "Eggsy" Unwin, 23 years old. Quit what was looking to be a promising career in the marines because he was worried (correctly) that his stepfather was beating his mother. Has no job to speak of, in part because he has a somewhat deserved reputation from engaging in petty crime as an adolescent, and in part because has spent most of the last year and a half taking care of his infant half-sister, which is also the reason why he quit taking drugs. Last seen over three weeks ago running for his life from his stepfather's gang, possibly in connection to a man in his early fifties with a probable expensive taste in suits, and a definite excessive taste for violence. Has not been seen nor heard from since. No I haven't found him, the trail is cold, and I am starting to think that the young man who gave me the information that was essential for solving what John described as the Tell-Tale Locket Case may be beyond my abilities to find." He raked a hand through his hair, and stormed away, coat flapping dramatically.

(Behind him, he could hear John chastising Sally. The words "insensitive" and "classist" came up, before Sherlock rounded a corner and could no longer hear the quiet but forceful – typical John Watson – lecture. In revenge, he solved all four of the current homicide cases open, including the one she had given him, in the space of about half an hour, explaining in scathing detail where knowledge he had picked up from the Irregulars was useful. He was unsure if she had got the point -typical thick-headed plodding police officer- but she was looking rather subdued, and John was giving him the look where he smiled with his eyes, and so Sherlock considered that he had come out ahead.)

Nine days later, and Sherlock's search for Eggsy was rudely interrupted by extremely well-trained thugs who proceeded to kidnap both him and Watson.