The woman in the cereal aisle at Tesco's that afternoon had been tall, curved in just the right places, and dressed to kill. Way too dressed-up to be shopping for oatmeal, anyway. John had only seen her for a moment, just long enough for short smiles and brief eye contact, but then she actually gave him a once-over as he passed her and even five hours later he couldn't get the picture out of his head. Women didn't ogle him all that much nowadays - the downside of looking ordinary, probably. Great that nobody expected you to be a serial killer, but terrible for picking up hot women at the supermarket.

Hot women with absolutely gorgeous legs. John rolled over under his blanket and groaned. No sound from downstairs - Sherlock was probably still sulking in his room, then, as he had been all evening. Not really "sulking" - "lurking?" Griping about John's totally unreasonable request that he get his bloody lab equipment off the bloody kitchen table every once in a bloody while?

Whatever. John slipped a hand inside his boxers and palmed his half-hard cock. Not that he'd let Sherlock's presence in the common areas of the flat deter him if he really needed a wank, but usually it was best to be prepared. Silent and under the covers (or in the shower) meant plausible deniability. John hadn't actually been on a date for a month and a half, damn it, and sex was (should be) a perfectly natural part of a person's life. Any person except Sherlock Holmes, apparently.

John let his mind drift back to the Tesco's woman, lingering over the memory of her hips and thighs and calves. Shortish skirt and heels - not slutty, just sexy. Straddling the line of "professional" and "evening wear." Heading straight from work for a night out, then? Not anywhere John was likely to go - he was definitely too old to troll clubs and bars for women a decade his junior - but then even just the fantasy was helpful. Helping. John tightened his grip and rubbed a bit more forcefully. Definitely helping.

Still no sound from Sherlock. This was for sure going to happen, then. John rolled over on his back to fumble blindly in the nightstand drawer for his lube, but something stopped him short. Wrong bottle - wait, two bottles? He pulled himself up to take a look.

His usual container of lube was gone. In its place were four smaller bottles, helpfully labeled "A" through "D," in a neat row. And a folded piece of paper which looked suspiciously like a spreadsheet. John had a sinking feeling he knew who was responsible for the swap, but he unfolded the paper anyway.

SAMPLE EASE OF APPLICATION APPROPRIATE VISCOSITY EASE OF CLEANUP

A
B
C
D

Right. No doubt Sherlock thought he had a perfectly reasonable explanation for all of this, but right now his complete lack of personal boundaries meant John had to either wank dry - which was not appealing - or use some sort of mystery substance which may or may not be appropriate for contact with human skin. The fact that it was actually a difficult decision said a lot about his current state of desperation. If only his bloody flatmate didn't make it so difficult to meet women-

"Ah, you found them."

John jumped about a foot in the air and slammed the drawer so fast he nearly caught two of his own fingers. "Sherlock! What the hell are you-"

Sherlock rolled his eyes. "It's obvious, don't you think? I've been working on this for weeks but I need more data. Just fill out the chart - a 1-10 scale should do; 1-100 would likely introduce spurious precision which might devalue the results."

John just stared. "Um. Working on what?"

"Lubricant, obviously," Sherlock retorted. "The commercially-available brands grow microbes at a significantly faster rate then they claim - the 'use by' date is a joke. I had time between cases and I have the lab equipment and this would actually be useful. Mind if I stay and watch? Or - oh, do you need a pen?"

Watch. As in, watch me wank? John cleared his throat. "Sherlock, bit not good. Again."

Sherlock's face slid into its default I-don't-understand-your-obsession-with-personal-boundaries expression. "It's not like I don't know you masturbate. Surely you don't suffer from performance anxiety?"

"Oi, I can get it up just fine when I need to, thankyouverymuch," John snapped back. "But Sherlock - really? You don't think it's maybe a bit unusual to present your flatmate with homemade lube and expect him to put on a show for you? I don't even know what's in this stuff - after what happened at Baskerville, I don't know that I'll trust you with unknown substances in or around my body ever again."

"Oh. That." Sherlock sighed theatrically and flounced from the doorway to the bedside, where he opened the drawer again and set the four bottles all in a row on the bedside table with their labels facing John. "Here, pick one. I'll stand over here so I can't see which letter you choose."

John hesitated, but then pointed wordlessly to bottle B.

"Fine." Sherlock popped off the top and squeezed a small puddle into his hand. "Totally harmless, you see? Not even knowing which one you picked, I can assure you they're all totally safe unless by some random chance one were allergic to silicon derivatives. And I know you aren't."

"You'd touch it even if it weren't safe," John pointed out. "I've seen you do it before, with that quote-unquote 'harmless' acid on the kitchen towels last month. Still not putting anything homemade on my dick, thankyouverymuch."

Sherlock rolled his eyes. And then unzipped his trousers with his clean hand and reached down inside his briefs to slick the lube around. John's jaw dropped.

"I've already got my own data recorded," Sherlock grumbled. "Although I suppose a single-blind test isn't the end of the world, for confirmation." He raised an eyebrow and nodded toward where John's lap was only partially concealed by his bunched sheets. "Go on, then - we can compare notes."

"I - you - the fuck?" John knew he probably should have had a much more coherent argument - he usually had no trouble telling Sherlock exactly which behaviors were crossing the line into totally unacceptable - but the linguistic processing centers of his brain appeared to have gone temporarily offline at the sight of Sherlock's long, slim fingers massaging his own cock underneath the fabric of his pants. The cotton pulled and shifted, drawing tight across a knuckle one moment and outlining a startling clear delineation between shaft and corona the next. Sherlock wasn't fully hard yet, but he was getting that way rapidly and John couldn't look away.

"Might have to save the numerical assessments for afterward." Sherlock's voice came out a touch breathy, like he was trying very hard to sound normal and wasn't quite succeeding. "Use - mmm! - use the same bottle, John. Will help reduce outside variables when I compare the data later."

John dragged his gaze from the mesmerizing motion of Sherlock's hand up to his face, but that wasn't all that much better - Sherlock's eyes were half-closed as he worked himself with strong, efficient tugs. John licked his lips and didn't realize it until his tongue was already sticking out of his mouth. Sherlock's own lips turned up in a half-smirk and he held John's gaze expectantly.

"Oh, for God's sake," he finally said. "Here - give me your hand. No, your left hand." He snatched up the bottle and poured a healthy dollop into John's palm. "There - use that."

Am I really doing this? Christ, I'm doing this. John gingerly reached down into his boxers and slicked the lube onto his cock. It was definitely interested in the proceedings, now, even more so than it had been when he was daydreaming about the woman at Tesco's. Given that the only thing on his mind since Sherlock burst in the door had been Sherlock, that was a somewhat disturbing revelation. Luckily, thinking about anything - much less having a bit of a sexual identity crisis - seemed to be beyond his brain's capacity at the moment.

Sherlock's whole posture changed the moment John actually gave in. He braced himself on the corner of the nightstand with his free hand, propping himself up, and started a very definite rolling movement with his elbows which had his hips twitching forward on the downstroke. He was very pointedly not looking at John, although it didn't escape John's notice that Sherlock's "vacant gaze off into the distance" was in fact directly into the mirror over the dresser. Which probably didn't show any more of John's lap than just looking straight down would have, but it was so quintessentially Sherlock to be covert in his observations and John couldn't suppress a little huff of laughter.

"I don't know what the hell we're doing," he said aloud. "What am I doing, Sherlock?"

"Masturbating," Sherlock replied, over-enunciating each consonant. "Wanking, jerking off, jacking off, pleasuring yourself, diddling, fist-fucking, having it off, rubbing one out, choking the chicken-"

"Fuck, stop!" John knew he was probably bright red - and that never happened, even when Sherlock was being a first-class berk - but something about hearing the rapid recital of synonyms in Sherlock's baritone I'm-rubbing-one-out-too voice was working on his libido in ways he didn't know his libido could be worked. "Just - don't, okay?"

"You like my voice, though." Sherlock didn't sound angry, just confused. "You haven't attributed sexual feelings toward it until today, but you regularly stop to listen even when what I'm saying can't possibly interest you."

"It's different when - when you're wanking, Sherlock. It just is." John slid his hand down further, a quick pass over his bollocks, then he settled back into the tug-and-twist he knew was usually his best chance at coming quickly.

"You like hearing - ngh! - hearing when my speech is impeded?" Sherlock straightened his spine a bit, even as he redoubled the intensity of his wrist movement. "That's - ah! - not uncommon in partnered sex. Nothing to be ashamed of."

"You're going to ruin your experiment," John retorted - the only defense he had left, but a good one. "Now your voice is a variable you'll have to include every time."

"Every - oh!" Sherlock sucked in an audible gasp and then froze, panting rapidly. And fuck, John could literally see the outline of Sherlock's cock twitching as he came. It was so wrong to watch, so Not Good and inappropriate for a straight flatmate to be mesmerized by, but John took in Sherlock's trembling posture and involuntarily tightened his own hand and then he was coming too, warm spurts of sticky moisture which would certainly necessitate changing his boxers and t-shirt and cleaning up before he could go back to bed. For right now, though, all he could do was to flop back onto his pillow and stare.

"Every time, John," Sherlock said quietly. He lifted his head and met John's gaze. "You said every time - that means you're willing to do this again?"

Christ. Every rational part of John's brain was saying no - he wasn't gay, this wasn't normal, what kind of straight flatmate wanks off with his male flatmate standing not two feet away? In the "yes" column, though, stood that fact that it had been one of the more incredible orgasms John had experienced in quite a while. And - despite his dating history - that title had quite a bit of competition.

Still . . . "You're utterly barking mad, you know that?"

Sherlock grinned, went to run his hand through his hair, and only just stopped himself before he smeared semen and homemade lube through his carefully disheveled locks. "That's a yes?"

"That's a yes."

"Excellent!" Sherlock yanked open the bedside table drawer, pulled out the chart, and extracted a pencil from his pocket. All left-handed. "Now - tell me. Ease of application? On a 1-10 scale?" He paused and glanced down at the remaining three bottles. "That was sample B, wasn't it?"