Disclaimer: Sherlock and its characters do not belong to me. This work is not for profit.
The strings always led back to him. He, of course, was just a name – the strings never actually led back to him. It amused him endlessly. He could hide in plain sight and watch them stumbling around after his strings as he jerked them along or see them pass him on their way through the supermarket, eyes drifting over him like any other stranger. There he was, the source of all their pain and frustration, sliding a jug of milk across the scanner. The cover was unnecessary, of course – he had the money and power to do as he pleased with his time – but his existence would be so utterly dull without it. The supposed challenge was still too simple, but he wouldn't trade the joke for the world – not that he'd need to. To all intents and purposes, he had the world already. No need to sacrifice the one laugh left worth living for.
He lived for that laugh, the last laugh, the pleasure of knowing the strings led back to him and using them to make his trackers dance. A detective, after all, was nothing more than a critic, following the steps of his artistry. Critics thought they knew so much, but they would never really understand the art until they picked up the paints themselves. Now wouldn't that be amusing, if he could get them to lay down their own strings across his stage. Not knowing it was his, of course, not until he swept it out from under them and they found themselves dangling from his strings.
One day, he supposed, he might consider showing them the face behind his name. The timing would need to be perfect, but he was the master of the last laugh, and that laugh would have to be his. They always were. They always would be.
And Jim Moriarty lived for the last laugh.
A/N: This came out of a challenge ("Write a nineteen-line narrative with a villain in it") that came with a prompt ("The puzzling identity is revealed"). It had me thinking about Sherlock, and this is what came out. The timeline for this is probably at some point before he meets Sherlock. The line about the detective as critic comes from Gosho Aoyama's Detective Conan, so I claim no credit for it.
