Blood is beautiful. Everything about it. Take that rich garnet red, a colour so real that other colours fade to insignificance around it. Or the living heat of it, because it's not just a liquid, it's alive. The elegance of its viscosity, a little thicker than water, lends to the way it drips and spills.
He loves the scent. In small quantities, it smells of copper and lightning. In large ones, it thickens the air with a stench of rich mouldering earth; the smell of fertile renewal, even in volumes large enough to signify death.
He knows it comes off as morbid to most people. It only gets worse if they know what he does for a living. He's even been accused of being a serial killer, so he mainly keeps it to himself.
People associate blood with death, is the problem. They associate it with pain, violence and disease. And they've got a point about the pain, but that's because pain is like blood. Any doctor or soldier could tell you that they're proof you're still alive.
So here they are again, Sherlock and John, patching themselves up in the bathroom. If they're less sliced up than they deserve for taking on a knife fighter hand to hand, they still look like they got the worst of it going a few rounds with a garden rake. John is scuffed, cut, and throbbing with pain he's finally beginning to feel, while Sherlock, across from him, looks like a defaced marble statue, streaked with soot and rust.
They're breathing. Bleeding. Smiling. Beautiful. Life demands more than observation from a distance, and John has never cared what Sherlock knows about him, so with no pretense he begins licking the blood out of the defensive cuts on his own forearms, setting the cuts to fresh stinging.
Sherlock puts down the antiseptic wipe he'd been cleaning himself with in order to watch. When John meets his eyes, they're laser-sharp.
Once he's got everything he can reach with his tongue, cuts shimmering with bright pain from the treatment he's given them, John rips open a wipe and briskly sets to work on the rest.
It's not pain that turns him on. He doesn't enjoy seeing people hurting. Blood, though…blood is the hot interior of the body, a smear of passion, a proof of living, breathing, fighting survival in the face of the odds. Because the odds are always against life. Life is a precarious tower always on the verge of toppling, that somehow manages not to tip its balance.
Sherlock is still watching him, ravenously curious, so John asks, "What does blood tell you?"
"It's a clue," Sherlock answers promptly.
"Of?"
He can feel Sherlock's eyes hooking, lifting, weighing him, and wonders what they see. "It can be endlessly communicative," Sherlock says after a moment, "in the right circumstances. Identity, genetics, health. A person's presence, position, path through a scene. Their death. I can map a person's life based on how, where, and when it falls."
John wants, then, but he isn't sure what he wants, so he says nothing.
...
Sherlock has his own relationship with blood, but John's never been sure of its nature. He can reconstruct a person's entire life from a handful of cells, but John doesn't know how to ask whether that means something to him beyond the satisfaction of acquiring data.
They're crouched on a rooftop, singed and laughing. John's pretty sure there's nothing more he'd wish for in the world right now.
Well. Maybe a tube of burn cream.
He holds up the knife they took, their prize for surviving the evening. "To think we almost burned to death for this." It's a beautiful thing, custom-made as part of a set. The maker's mark is engraved in tiny characters on the bolster.
John feels drunk with altitude and risk, and probably also smoke inhalation. He hands Sherlock the knife and asks him, "What does this tell you?"
Sherlock turns the knife in his hands thoughtfully, admiring its shape and the glint of the blade, testing the edge delicately. Then he turns the same look on John. "It's been prepared for use," he says finally. "On someone."
"On someone?" John holds out his hand to take it back, so he can look.
"It's been sharpened and disinfected. It's not a cooking knife, but it wouldn't need to be this clean if hygiene weren't an issue." Sherlock takes John's wrist with his free hand so that their inner wrists both face up. "The question is, on whom?"
John's lips part as the blade descends till the point dimples the soft skin of his inner wrist. Sherlock smiles and presses just that little bit harder. John would close his eyes but he can't look away from the little stinging split in his skin.
Sherlock lifts the blade away to let the drop of blood well up, a tiny gem of consummation whose heat spreads through John's body.
And then his eyes lock on the flashing knife as it descends again, to prick at the skim-milk white of Sherlock's wrist. John might make a noise when Sherlock's skin parts and a red bead blossoms on Sherlock's wrist to match the one adorning John's.
Sherlock smiles, sly and inscrutable, into John's eyes and sets the knife down. Anticipation blooms as hot in John's gut as Sherlock's grip on his wrist.
...
John controls his breath ruthlessly, in time with the knife's movements through his flesh—slow, steady, and deep. Sherlock's hand splays out across his abdomen like a warm crab, thumb and little finger spanning from point to point of his pelvis in a reminder to keep still. It's smeared with John's blood, ivory and crimson, and John thinks he's never seen such a work of living art.
Sherlock glances up from where the tip of the knife is sunk into John's flesh and bends to kiss at the welling line it's left behind. When the tip of his tongue parts the wound, John gasps in delighted pain.
Blood trickles down Sherlock's left breast. John gasps again, struck with the pang of needing Sherlock in him. Soft hair twists in his fingers, coaxing Sherlock up till John can press his lips to the cut beneath that graceful arc of collarbone and let the iron coat them.
Sherlock makes a soft noise, something like startled approval. They turn their heads at the same moment to bring their mouths together, their blood mingling on their tongues.
He can feel Sherlock's eyes grazing over his wounds, sinking down into his body, cataloguing him, knowing him. John shivers. "What does blood tell you?" Sherlock asks.
He reaches out to brush Sherlock's scraped knuckles. "It tells me we're still here."