A/N: Bolded sections are quotes from 'Foxfire' by Joyce Carol Oates.

The strangeness of Time. Not in its passing, which can seem infinite, like a tunnel whose end you can't see, whose beginning you've forgotten, but in the sudden realization that something finite has passed and is irretrievable.

"No one could fake being such an annoying dick all the time," says John, and the clear, plain expression of amused faith in his eyes is everything Sherlock needs, has needed ever since John first innocently followed his dictation of that message to the serial-killing cabbie and then saw that pink suitcase sitting there in their first adventure together and took the apartment anyway, trusting him. Him.

"Moriarty wants me broken," he hears himself say. "He wants me dead." He doesn't say and what Moriarty wants, he generally gets, but it's there, anyway, hanging between them.

"He'll have to get through me first," John says, only half smiling, and Sherlock remembers John in a bomb vest beside a swimming pool and is up and moving around to the window before he can even think, breath ragged and desperate as he pulls John into him, wrapping long arms around his shoulders and waist and breathing deep the warmth of his hair, feeling the soldier's heart thrumming against his own body, pulse bright and fast and full of life, and he thinks I won't let you die, not for me.

"I believe in you," John whispers, and leans up and kisses him, lips warm and fervent and sure against his own. Sherlock's lips are cool and slightly unsteady in comparison, but he presses back all the same, tasting him, mapping the curve of his mouth and tongue-tip, committing each movement to memory.

It's not their first kiss - far from it - but Sherlock knows it might be their last, and he tries to pour everything into it, eloquent as dust. He thinks, silently: I love you and Thank you and You have saved me, so many times.

Eventually he just thinks, John.

And then John is pushing against his chest, walking Sherlock back to their shared bedroom and barely breaking the kiss, kicking aside the chair and the violin case and the stack of music compositions that don't matter because Sherlock will never get around to playing them, now.

This may be the last time I will ever taste your skin, Sherlock thinks, kissing his way down the man's warm chest as their shirts slip to the floor, unnecessary. This may be the last time you will ever unbuckle my belt, and if their lives were hourglasses then his would be tinted, hidden, and he would think This may be the last moment of sand I can ever give you.

Cool sheets press against his bare knees as he lays John down on the soft whiteness of the bed, and holds him there, forehead to forehead, as if he can be that man on that stupid TV show John likes watching. As if he can pass the unspoken thoughts through the barriers of naked flesh and bone.

He wishes, more than anything, that he could share this hollow ache with lover twists beneath him, as if to lie on his back, and Sherlock halts him with a hand on each shoulder and a look of slight hurt on his face, and he knows from John's eyes and the way he lies back and lets his thighs fall apart that he understands too much - and not enough.

This is the last time for me, he thinks, reaching out for the little cylinder on the bedside table and untwisting the lid. The gel is cool and slick against his fingers as he prepares John, quiet and soft and sad, and he would be even slower if Lestrade wasn't on his way to Scotland Yard to procure a warrant. This is the last time for us, he adds, too, watching John's chest shudder as he takes a breath at the second finger, then the third.

He wonders, a little jealously, if it will be the last time for John, who will go on, bright and shining in a world full of living men and living women, and he thinks conductor of light and knows he was wrong, because John Watson has a fire entirely his own.

The heavenly light you admire is fossil-light, it's the unfathomably distant past you gaze into, stars long extinct.

He lifts the man's hips, fingers splayed across his backside as he pushes his way in, lingering and slow and gentle, watching John blink. Watching him breathe. He wishes he had hours just for that; years, even. But he has mere minutes - ten, fifteen at most.

He refuses to rush this, all the same.

He lowers himself gently, resting his chest against John's body, skin to skin. He can feel their hearts thrumming together through their ribcages, moving in time with each other in this long, slow dance. John's arms reach up and splay across the firm lines of his shoulder blades, pulling him closer, wrapping strong calves around Sherlock's legs as he reaches up for another kiss, his length hard against Sherlock's stomach.

There is friction, and movement, and heat, but Sherlock's more interested in mapping out a memory of John with his fingers and tongue, relearning the curved shells of his ears and shoulders. He already knows them, of course, but all knowledge is useful; even now he is reinforcing his knowledge of the exact pressure of tongue against hollowed-collarbone that makes John jerk his head back, expose a milky throat for Sherlock to press his eyelids against and hide his tears.

He cries silently into his best friend's neck as his hands continue to glide across the firm lines of John's body, filing this memory under all my life and wonders whether he can measure the rest of it in hours or days.

He groans into John's mouth as he spills inside him, pulse beating a tattoo of yes into his neck as John floods the millimetres between them with warm come, and in their post-orgasm haze they cling together for the last time, and Sherlock thinks God and all his angels are exquisitely cruel.

They rest for what he can only think of as an abridged eternity before John's phone begins to buzz from the other room, and John unpeels himself from Sherlock's unwilling arms and says, hesitantly, "That -that'll be about them."

Sherlock nods and watches him go; hears the words warrant and bastards and thank you, Greg float through the open bedroom door, and he swings long legs off the bed and says, "I love you," into an empty room.

It's much later - years later - that he raises a fist to knock on John Watson's door, hesitant and uncertain and expecting to be punched in the face at any point in the next thirty seconds.

But, he thinks, standing on the edge of John's life, you can turn hourglasses over, start again, and the same old sand will run a new course. Grains, infinitesimal and beautiful, will shift together.

The door opens.

A flame is real enough, isn't it, while it's burning? Even if there's a time it goes out.