Genius may have its limitations, but stupidity is not thus handicapped.
Carl "The Cardman" Connors loved his job. Easy money and no risk whatsoever: take possession of bank cards and the like from those who 'acquire' them but lack the skills to use them safely and, via runners who couldn't be traced back to him, send them along to those who could, earning a tidy profit for his efforts of course.
He maintained some scruples with how he worked, although less due to moral issues and more as a result of common sense. If you acquire your merchandise as a result of grave bodily harm, don't come to him and expect him to take it off your hands; he wasn't getting anywhere near anything that might become a murder investigation. And don't even think of nicking anything off a copper and try to pawn it off on him, coppers were tenacious buggers and if you crossed them you deserved what you got.
His rules were well known, he had no qualms rolling over on anyone who broke them, which was why he was stunned when Thug, Slug and Bug (not their real names, of course, but they were brothers and their surname was something completely unpronounceable so when someone stuck them with that nickname a few years ago it stuck) showed up talking about "teaching that meddling ponce a lesson" he began to fear the story behind the wallet they were shoving at him.
"This isn't a copper's, is it?" he asked, his hand hovering a few inches away from the proffered item.
"Nah, y'know we'd never go after one of those, not after the last time." Bug, as always, spoke for his brothers. Carl sometimes wondered if Thug and Slug, towering massively behind their brother, had ever even mastered the powers of speech.
Still a little hesitant, Carl took the wallet and was just about to pull out the cards and various detritus within it when Bug added, "It was that little hanger-on, you know, the one always trailing behind that creepy looming freak. We were just minding our own business, checking some back doors," which Carl translated as trying unsuccessfully to break into some shops, "and there he was, strolling down the alley like he owned the place or something. So we jumped him. Little bastard was a handful though, got a couple of good licks of his own in, even managed to knock out the dummy here," he hiked a thumb over his shoulder at Slug. "But a couple of good fists to the kidneys took care of that and he went down like a tonne of bricks."
Carl wracked his brain trying to think of who the hanger-on and looming freak Bug could be talking about could be. The answer struck him like a bolt of lightning the moment he opened the wallet and saw the name John Watson.
"Oh, shite. Shite! Fucking hell, don't you have any idea what you've done? The freak is Sherlock Holmes, you morons. Tell me you didn't hurt Watson that much." The three looked at him with blank, sheepish stares and hastily cleared their throats, shrugging. "Holmes is worse than the cops, especially when he puts his mind to it, and you've hurt Watson. His Watson. Idiots. There is no way he's not coming after you. Here," he shoved the wallet back at Bug. "Take this, take this and get the hell out of here. I don't know you, I've never heard of you, and if I ever see you darken my doorway again I'm calling the cops on you myself. Now, go!"
Ignoring their protests, Carl shoved them out the door. "Shite," he muttered as he quickly locked up behind them, "Holmes is going to go spare. I gotta lie low for a while. Or maybe find someplace to hide. Cornwall's supposed to be nice this time of year. Always wanted to go to Cornwall. Yeah, that sounds good, he'll never find me in Cornwall. Who'd think of looking for me in a place like Cornwall?"
"Who indeed?" a voice called out from behind him.
Carl spun around. "Oh, fuck me. Sherlock Holmes."
"Now, I have no intention of doing anything that unpleasant, I do have standards after all. However, I do believe you have some information I desire and I am quite sure you're willing to share it with me, am I correct in that assumption?"
"Yeah. Of course." Carl swallowed heavily, shuddering at Holmes' tone. If he got out of this alive he was definitely going to Cornwall. A vacation sounded like a really good idea right about now.