I'll admit I didn't really want an elaborate set-up. The pool confrontation is convenient because it's a scene in which Sherlock, John, and Moriarty are all together in the same place at once, and Sherlock and John are at Moriarty's mercy. So, my fill is set in an AU in which Moriarty kidnaps Sherlock and John during the confrontation at the pool, with the sniper guns being loaded with tranquilizer darts.