Just because the idea amused me.
Boundaries
John shut his eyes with a frown and blinked them open again with his head tilted.
"Sherlock, what exactly…?"
The detective snapped his attention back to the man he had pressed against the wall and an annoyed look flashed over his face.
"Couples John! Couples do this," and with that his attention diverted back to somewhere off to John's right, leaving the doctor blinking in a mixture of bewilderment and exasperation. His mouth opened and shut as his mind tried to push its way through the mire and tangle of what Sherlock's logic could possibly be whilst forming his scattered response of…
"But…we're not a couple Sherlock!"
At which point the detective clapped a long-fingered hand rather unceremoniously across the unwilling doctor's mouth and hissed that if he wasn't going to be useful he could go home. John did try to point out that he would rather go home but the hand over his mouth and the compromising position they were in didn't really give him much room to make it.
The genius was staring off to the side for some considerable time before his head snapped back to face the doctor, smiling brilliantly.
"Oh…oh! How elegant! How wonderfully elegant! We have him John! We – have – him!" and with that he abruptly released the disorientated doctor and darted off.
It took the poor doctor another moment for his brain to catch up, at which point he turned his head and stared off into the darkness where Holmes had disappeared. A puzzled look was on his face, which morphed into resignation and a sigh.
"I thought we were just going to get milk."