Trapped indoors by a thunderstorm, they'd been restless all morning. Holmes finally settled down with his hair-trigger and began to make a neat row of bullet-holes in the mantelpiece, despite the Doctor's requesting, demanding, and then outright pleading for him to desist.
Receiving only a testy growl, Watson resigned himself to another nerve-shattering afternoon and busied himself about the flat while the gunfire kept time with the thunder, putting away papers and books and making the place more respectable. He wrote a letter (or tried to), sorted the post, and began to take inventory of his medical supplies.
Holmes was on his last half-dozen cartridges when, after a shot that coincided with a monstrous burst of thunder, he heard glass shattering behind him followed by a muffled cry of pain.
"What's the matter?" He peered over his shoulder at the table, where Watson was cradling his left hand close to his chest and reaching for the water decanter.
"Bad timing," the Doctor gasped, losing no time in pouring the water over his hand. "I was holding that phial of Prussic acid…ouch, don't!"
Holmes had taken the injured hand in his own, wincing at the sight of the reddened skin, swollen despite the prompt rinsing. "I startled you," he stated, flushing with guilt.
"Not just you," the Doctor sighed, gingerly flexing the burned fingers. "The thunder…just bad timing all-round. I spilled it everywhere, too."
Holmes was about to lecture him on the idiocy of cleaning the table before his own hand but thought better of it. A surgeon, and a writer, needed the use of his hands, and his poor friend's face was already assuming a mournful expression. He reached into the open bag and removed some cooling ointment, making as if to begin treating the injury.
"I can manage." The Doctor pulled his hand free, glaring in obdurate stubbornness.
Holmes blinked placidly and uncorked the bottle of ointment. "No doubt. Now keep still, do."
Watson muttered under his breath but finally gave in, wincing as the detective began to carefully daub the thick cream over the burn. "Will you – ouch! – now will you stop turning our sitting room into a firing range?" he demanded. "Besides shattering everyone's nerves, you're liable to destroy something badly enough that Mrs. Hudson will throw us out!"
"After seventeen years?"
"And I'm sure the neighbours are no more thrilled about the gunfire than they are about your violin solos at two in the morning…ouch!…Holmes, for pity's sake! It is no wonder you were banned from several of the classes at St. Bart's."
"Just hold still," The detective scowled, corking the bottle and unwinding a roll of bandaging.