It started off as a game, a simple matter of seeing just what bonds exactly Sherlock was capable of breaking. Handcuffs were laughably simple, as were square knots. So they branched out, got creative. It was fun; it was silly. Until it very suddenly wasn't, and then Sherlock found himself strongly bound, bitter and petulant, refusing to give up, snapping out insults, heat rising in his flesh. Until John Watson had him at his mercy, if only for a short moment, and then lips were crushing against each other, and bodies were writhing against each other. Helpless moans and gasps filled the air, desperate needy little sounds. The hands of one flew over the body of the other, driving both to distraction, before pulling hardened flesh free from trousers and sliding unceremoniously over it. A yell was bitten back, a moan was pushed against damp skin. Hips skittered nervously, bucking like newborn colts, and just as suddenly both men were shouting, spurting, shuddering, collapsing. It had started as a simple game, nothing very serious. But it had become something altogether different all too quickly, something darker and more delicious. And when John cut Sherlock free and helped massage feeling and life back into the long, sharp limbs, both men found themselves more than eager to repeat the experiment.