The problem with being absolutely certain that one is ready for every eventuality is that by the time one is proven wrong—as one invariably is—it is almost always too late to account for the one exception.

Sherlock Holmes stands in the smell of chlorine and gentle sloshing sounds of water in the pool filters, and holds the data stick in the air, and is absolutely certain he is ready for every eventuality.

Then the exception steps out.

Condition A: Only the bomber knows he will be here.

The shock, he will tell himself later. It is the shock that does it. Who wouldn't be shocked? Him, though, that's who, he is never shocked because he is always right. He does not recognize shock when it comes.

Condition B: John is here and is expecting him.

This is what he notices when John steps out and looks at him: not the tense set of his jaw, the rigidity of his shoulders, not even the bloody parka, never once seen beforeand overwarm for the weather to boot. What Sherlock notices is what anyone might: hands nonchalantly in pockets, the outwardly calm way he meets Sherlock's eyes.

Conclusion C: …

For twenty one terrible seconds, Sherlock's mind is not his own.

Myfriend, says his mind, but then immediately replaces it with "colleague," and then replaces it again with "friend." Because he knows "colleague," a colleague helps you and works on your side and what they feel or think about you is largely irrelevant. He's had colleagues before. He's had enemies too, plenty of enemies, but enemies do not move in with you or tell you how brilliant you are in a voice of quiet awe or fuss when you don't sleep or nag you to buy milk.

Do friends do that? Sherlock doesn't know.

Do friends strap hostages to bombs? Insufficient data. Unnamable variable. He gets even that far and still doesn't get it, doesn't see.

John stares back at him. Time moves at underwater speed, as though they are in the pool instead of beside it.

He doesn't have friends, he decides to remind himself. He has enemies. The closest thing, his brother says.

"Evening," says John. Sherlock sees the dryness of his lips, the nervous flicker of his eyes. He does. Sherlock sees, but he does not observe.

He looks at John, and John looks at him, and Sherlock's mouth opens a little, but he doesn't say anything. And still Sherlock does not understand.

"This is quite the turn up, isn't it, Sherlock?"

He feels the disconnect between himself and his logical brain, but doesn't know what it means, cannot identify what it is he's missing as a result of it. He knows he's missed something—his bloody flatmate is standing with his hands in his coat pockets by the pool where Carl Powers died, he has missed something—but when? where? He can't use his mind. He feels like he is drowning inside his head, drowning like young Carl Powers. All he sees is John Watson.

"John," says Sherlock's thick tongue. John Watson. It comes out hoarse, his lungs not possessing quite enough breath for the name. John Watson. "What the hell—?"

"Bet you never saw this coming," says John Watson.

John Watson. John Watson. It is John Watson speaking, but who is that? John Watson doctor John Watson soldier John Watson flatmate John Watson idiot John Watson genius John Watson friend-colleague-friend?

John Watson enemy?

his mouth open like gasping for air underwater why can't he just think why can't people just think when did he become people

If John Watson is his enemy, does Sherlock really want to win?

he is just so tired

But as soon as that stray, drowning thought passes through his head he meets John's eyes—really does, this time, and it is all of Sherlock looking—and he sees that John is tired too. Sherlock has been awake for 78 hours and has been keeping John up for some 40. He knows that, afraid of how long he will end up sleeping, John has not yet allowed himself a nap. Sherlock observes in himself the slight heaviness of limb associated with impending bodily weariness, and observes in John his bleary eyes and the bags underneath, despite the adrenaline he's operating under.

And then, a moment before John opens the parka to show him, he observes the semtex vest. Everything suddenly gets clearer, his mind unfogs all at once and the pieces click into place and yet somehow it isn't actually any easier to deal with than it was.

John Watson, friend. It's so much more terrifying than John Watson, colleague or John Watson, enemy.

The red light appears on John's chest, and all the possible eventualities change at once.

Sherlock isn't ready for any of them.