For a fire to be born, you need optimum conditions; the perfect mix of oxygen, fuel, and ignition. At least 16% oxygen, just like open air. Just a spark, too, a very little one, like the one arcing from the broken switch main on the wall.

And fuel, like the sweet hit of organics that John can smell from the petrol spreading across the floor in a dark wave around his feet.

Sherlock's out cold, felled by a blow to the head exactly like the one John got when they snuck through the warehouse door. A tiny trickle of blood traces its way out of his hair and along his temple, threading its grisly way down his cheek and to the point his face is in contact with the floor. John scrambles over to him and sighs in relief at the warm breath he feels across his hand, the steady thump of Sherlock's pulse in his throat. John feels for the knot on his own head, and pulls his hand away sticky and red. He can only attribute that he woke up first to the strength or accuracy of the bloke that hit him, and he's feeling woozy and a little sick. He's obviously concussed, but if the growing smell of petrol is any indication, they need to move, quickly.

He looks at Sherlock, all six-foot-one, one hundred seventy pounds of gangly dead weight of him, and realizes there's only one way to do this, and it's going to hurt.

John gets into a crouch, shoves his hands under Sherlock's arms, and hauls him up until John's holding him, almost hugging him in front of his body. Sherlock's head lolls to the side, his mouth open and John cringes at the sight of it, a flash of another man working its way into his consciousness. John drops his shoulder, folding Sherlock's body over his, and reaches behind his head with his left hand, ignoring the sickening twist and pop of his shoulder. It's instinctive, the shift and pull of Sherlock's limp form until he's draped across John's back, one hand wrapped behind Sherlock's knee and the other locked into the crook of Sherlock's elbow.

The smell of petrol is getting stronger, and John spares a quick glance at the pool making its way across the floor before he takes a deep breath and straightens up, nearly staggering under Sherlock's unexpected weight too far over on one side. Those legs might be skinny, but they weigh a ton, so John stops for a moment, wiggles Sherlock's body until it's balanced properly and curled around his, locks his hands together and sets off for the nearest door as quickly as he can.

It's been three years since he's had to carry anyone this way, and the weight of Sherlock across his back feels like a phantom limb; the feel of the straps of his pack cutting into his shoulders and the frightening rapidity of Chase's hot blood coursing into his collar and down his back is beating itself back into his consciousness until the sensation overwhelms him and he has to stop. John closes his eyes, sucks in a deep breath to steady himself, and pulls grim determination up from the depths to turn and thread their bodies through the door. He prays like anything that whoever left them there to die didn't wait around to watch the tableau play out.

Fortunately no one tries to assault them as soon as they make it to open ground, and after a quick look around, John sees no faster options for getting away from the door other than straight down the alley and into the street. The route is dicey; if there is someone waiting, he and Sherlock will be utterly without cover for about one hundred yards. His shoulder is screaming protest, the angle of his arm wrapped around Sherlock's awkward and strange after so long without training. He's not sure he's got the strength to make it the entire way to the street.

It won't be a big explosion when it happens, but the flash fire will likely reach into the alley, and John just wants to get them as far away as possible before it happens. But just as he starts to take a step toward the street he feels tension coiling in the long body over his shoulders. He stiffens, realizing Sherlock is starting to stir. He hopes that panic isn't Sherlock's first reaction upon waking up; otherwise he'll end up on the pavement head first, most likely.

"What the hell?" he slurs.

"Just hold still a minute," John grits out, trying to focus on putting one foot in front of the other as quickly and steadily as possible.

"But I – "

"Just shut the hell up for five minutes, I am begging you," John rasps. His lungs are burning with the exertion, and now that Sherlock is awake, he could probably put him down. But there's only about 30 yards to go, and he knows it'll just be faster to keep going. Momentum pushes him forward, and as they reach the end of the alley, he hears the distant whump and flare as the petrol catches, blowing a hot wind across the back of his legs and causing Sherlock to tuck his head against John's shoulder.

The most sheltered spot John can find is the stoop of the building next door, so he stops long enough to let Sherlock slide off of his shoulders and land, a little unsteadily, on his feet. John pushes Sherlock down on the top step and slides his fingers into Sherlock's hair, feeling for the cut he knows is there. It's longer than John expected, a nasty gash that needs stitches. The thought of Sherlock's face when they shave off a patch of his hair to do it sets John off in a fit of relieved giggles.

"You're going to look like a porcupine," he laughs, "and for the love of God, try not to get knocked out next time. You've had too many concussions as it is, and my shoulder can't take another run like that one." John kisses Sherlock's forehead, glad they made it out without more trouble. He feels a little lightheaded himself, trying to clear his head as he massages his shoulder, rotating the joint and feeling the bones grind slightly. His shoulder feels a bit looser, actually, and John realizes the adrenaline rush of trying to get Sherlock and himself out of that building let his body ignore the pain of breaking loose scar tissue that was too painful to move during physiotherapy before. He twists his arm a bit and looks up to see Sherlock staring at him, his eyes still a bit hazy.

"You never complained about taking my weight before," Sherlock slurs. "Matter of fact, you seem to like it."

John shakes his head. "Save it for later, yeah? You need an eval." John pulls out his mobile and hits #3 on his speed dial. "Lestrade? Of course it's us, who else would you think? Well, we could use a ride to A&E. Yes. Again."

"John," Sherlock calls from the sitting room. "Move these boxes with me, would you?"

John rolls his eyes. Ever since he managed to haul Sherlock's dead weight out of that warehouse, Sherlock's been asking him to do more and more of the lifting and carrying than he's used to. Admittedly, it's helped keep his shoulder pretty limber. Curiosity drove him to get a guest membership to the gym so he could do a few lat pulls, the first in over a year, and it felt pretty good.

But really, he huffs as he picks up the third tote full of God-knows-what Sherlock had delivered and hauls it upstairs, it's like Sherlock's just inventing things for him to shift, and it's getting annoying. That is, until he turns around from lifting the last of the crates onto the stack and sees the intense, hungry look on Sherlock's face; the one that never fails to send a shock of arousal through John's body, the one where Sherlock looks like he could devour him whole. John stops and stares for a minute, deliberately giving Sherlock a good once-over, just to see the flush rise on the other mans neck and his eyes darken.

"How much of this junk do you actually need?" John asks casually, as if he's not watching Sherlock's dick get hard under his trousers.

Sherlock ignores his question and poses one of his own. "How much could you lift before you were shot?"

John looks at him carefully, a little curl of suspicion unfurling in his mind. "Depends. Are you talking bench press, deadlift, or what?"

"Either. Both."

John shrugs. "Last I was in the weightroom, I could bench about 195, deadlift 225. Leg press 300."

John watches Sherlock's eyes widen slightly. "That's quite a bit for a man of your stature."

"Yes, well, not any more. Surprised I could get you over my shoulder, honestly. The walking wasn't too bad once I did, though." John shifts slightly, the tension between them tightening, coiling, and ready to snap.

Sherlock starts fiddling with the edge of a newspaper hanging from the edge of the bookshelf, and looks at John from under lowered lashes. "I find myself thinking about what happened fairly often, concussion aside," he says.

"That so?" John says as he steps up to Sherlock's chest, effectively forcing him backward until he bumps against the wall. John reaches down slowly, working on Sherlock's belt, his buttons, his zip; all the while watching him become more and more unfocused, his body slumping against the wall, knees barely holding him steady.

John gets his trousers and pants down, lets Sherlock balance against his back as he pulls off Sherlock's shoes and socks. When his bottom half is naked, John leans in quickly to kiss him, hard.

"Let me guess – you were wondering just how much I could actually hold," John says, and shoves his own trousers down.

Sherlock nods and bites his lip. John reaches behind Sherlock's thighs and encourages him up into the cradle of his hands, bracing Sherlock's back against the wall and feeling those long, long legs wrap around his waist. Sherlock's not nearly as heavy this way as John thought he might be, and as a matter of fact, this could work out very well. John feels a smug smile tug at his lips. Oh yes, he's definitely going to take advantage of this.

John kisses him, slanting his mouth across Sherlock's lush lips. The angle is odd, there's no lube anywhere in sight, and it's not like he's had a lot of time to get Sherlock ready, but he's going to do this if it kills both of them. The last time he had anyone against the wall was more than a decade ago, and he hasn't felt the need to do it again until right bloody now. Right now, when he realized he still could.

"God, Sherlock. Can I just?" John pants against Sherlock's mouth.

Sherlock just kisses him harder, pulls back, and spits into his hand. He slithers his long arm between their bodies, and before John can blink, Sherlock's shifted enough for John's cock to press against his slick opening.

"Tilt up a bit," John says, and feels Sherlock's hips move in response, making the angle a bit easier for both of them. He uses his fingers to line up a bit, and slowly pushes his way in. He can tell Sherlock is fighting to relax, his deep breaths pushing against John's chest. John stops about half-way, pulls back slightly, bears forward again and doesn't stop until Sherlock is nestled against his hips.

"All right, there?" John asks.

"Fucking hell," is Sherlock's breathless reply, so John takes that as a confirmation and begins to move. His slow, purposeful shoves against Sherlock's body are short and controlled for fear of losing focus and dropping Sherlock, and in this position who knows what damage could be done to either of them. But the more the sharp heat of Sherlock's body surrounds him, the more Sherlock claws against his back, chanting "More, harder, harder, fuck, yes, yes, yes" in his ear, the faster he thrusts, all but pushing Sherlock's back up the wall with every smack of his hips into Sherlock's rear until he feels the bright sparks of his own orgasm skittering along his nerves.

"Are you close?" he asks, adjusting his grip on Sherlock's thighs, which are becoming increasingly slippery with sweat. His shoulders are burning with the effort to both hold Sherlock in this position as well as try to fuck him, but the adrenaline pulsing through his body and the satisfaction of actually pulling this off keeps him going.

"So close," Sherlock answers, unwinding one arm from around John's back to rub himself in time with the motion of John's body. He sucks a breath in through his teeth, and releases it on a groan as his orgasm hits him hard.

The reflexive tightening of Sherlock's body on John's cock has him suddenly hurtling toward his own orgasm, unable to stop it if he tried. He comes in short, quick bursts, and before he's barely finished he starts to lose his hold on Sherlock's suddenly dead weight. He's about spent, his muscles trembling in protest. "Christ, Sherlock, down you go. You're going to kill me."

Sherlock unwinds one leg at a time from John's waist, putting his feet on the floor as John releases his weight. They stand together for a moment, John's forehead leaning against Sherlock's shoulder, both breathing heavily. That was not at all what John expected when Sherlock had asked for help, but he's certainly not disappointed at the result.

"Fullfill that little fantasy you had?" John asks eventually, and flattens his hands against the wall on either side of Sherlock's body, nosing open his collar and kissing Sherlock's smooth throat. They really should go clean up, perhaps take a little nap. John's starting to think sleepy thoughts when Sherlock's voice cuts through the post-orgasmic haze.

"More than fulfilled, John. Once we're showered, I want to show you a little something I found on page 53 of The Gay Man's Kama Sutra. It's called "The Wheelbarrow." I'm sure now that you're up for it." Sherlock's slides out from between John's body and the wall and saunters off toward the bathroom, leaving John staring after him, shaking his head and rolling his shoulder. Doesn't feel too bad, all things considered.

Oh, what the hell, he thinks, shedding his shirt on the way to the bathroom and calling out, "Hey, how much of you do I need to hold for that?"

sees the heated, intent expression on Sherlock's face when he lifts the last crate to balance on the stack.