Some people are givers. The photosynthesizers of humanity. They live off sunlight and give away—well, whatever life really means—when the clouds pass over. There is not one in every crowd, but they do manage to join every crowd—generally. The last and most important distinction is that they will not recognize themselves in this description.

John Watson was a soldier. Perhaps it is more descriptive to say he was a killer born—if a killer can be born instead of evolving from a small, soft-edged child with ruffled blonde hair and wide blue eyes. In any event, when John threw himself into combat for the first time (it is not pushing the boundaries of hyperbole too far to say that combat threw itself into John), he knew that he had been thirsting all his life for dry desert air and the heat-shimmer-sheen of adrenaline and the eloquent whistle of bullets to shatter the stillness. (The later Bullet, that shattered more than stillness, was an Unfortunate Complication). Who knew that the nocturnal wailings of a sandy-haired infant could be translated into British Non-Infant colloquial as…

"Bored."

John Watson threw a pillow at his flatmate. It hit him squarely in the chest instead of the face, which is how Sherlock knew that despite appearances (newspaper and telly and obligatory cup of tea) John was bored too.

The question was how bored. All worthwhile experiments contain an element of risk.

Sherlock shifted onto his back above the protest of sofa cushions and turned his gaze to the ceiling.

"Mind you," he drawled, twiddling his thumbs in a calculated simulation of mindlessness, "I suppose there's a chance my mind would depart this insupportable state of ennui if you let me test the flash point of the sorry-looking casserole in the oven, or if I had reason to believe you disrupted the experiment of several weeks that's unfolding in your sock drawer…I assume you did have the sense to purchase new ones?"

John's knuckles whitened around the remote control, he unleashed a torrent of swearing, and Sherlock knew it was Bad.

The detective refrained from commenting on fixed variables and how he should've saved that batch of bacteria for the casserole and pretended to visit his mind palace while pretending to watch crap telly. In reality, he was watching John. Who was making a concerted and nearly invisible effort not to clench and unclench his left hand.

That's when Sherlock knew it was Dangerous.

There wasn't a lot you could do when Dangerous occurred, except growl at people in a manner more snide than usual to ensure that they Stayed the Heck Away, which was safest for everyone. Or better yet, hope that you were sprinting through an abandoned warehouse or the backstreets of London somewhere chasing down someone who, in all likelihood, was scared but Not As Scared As He Should Be. Which was not safest for everyone—but if Lestrade wanted his quarry unscathed then he should make an effort to keep up.

In more ways than one, mused Sherlock, steepling his hands in order to appear to be thinking too hard to be thinking about what John thought he was thinking about, which was irritating because that was the one time John's thinking usually led him to an accurate conclusion.

This time, however, John's thoughts were too concentrated on clutching his tea in his extremely steady left hand to bother with reading Sherlock's. All in all, the familiar quick tread signaling the imminent arrival of Scotland Yard and peril was more of a relief than otherwise.

Out the door in under a minute, tea and token protests abandoned, the celebrated Mr. Holmes flying down stairs still winding his scarf in its usual complicated knot, and Lestrade wondering at his considerate haste—and only the consulting detective noted, with considerable satisfaction, that the good doctor strode along without the trace of a limp.