Blame this on asteraceaeblue and her science class. She's the one who explained to me that you need to oil a microscope lens for 100X magnification because "the resolution is so high that the oil is needed to create a 'tunnel' of sorts between the slide and the lens…it refines the image and reduces light refraction."

All very innocent and sciencey, yes? Um…no. Because instantly our minds went into 'wink, wink, nudge, nudge' mode, and the following (sorry, non-explicit) ficlet was born.

"Hello, Mrs. Hudson, how's life been treating you?"

John leaned over and gave his former landlady – but never housekeeper! – a peck on the cheek as she greeted him at the front door. He still had a key, of course, especially since he'd returned to helping Sherlock on cases, but she'd been on her way out on a date when he'd popped by. There was no case on, hadn't been for over a week, but Mary had told him in no uncertain terms that she needed him not to be hovering over her like a mother hen just because she was a few days past her due date.

The fake Moriarty case was resolved, the Magnussen issue had been swept under more than one governmental carpet, and Sherlock was once again a free man, in residence at 221B Baker Street and available to NSY and the general public for consultation.

Except, oddly enough, Greg Lestrade said he'd been turning him down, even for a very tempting 8. John thought it was because of Mary being past her due date, but it had started even before then – and besides, Sherlock had predicted that the baby would be born after the 12th, which was still a few days away, and Mary had seemed to agree even if her OB and John both thought otherwise.

So here John was, off to pester his best friend – whom he hadn't actually seen in a week, now that he thought about it – into telling him what, if anything, was wrong. When he explained his reasoning to Mrs. Hudson, and how he fully expected to find Sherlock either in a gun-shooting strop or sulking in his rattiest pyjamas while curled up on the sofa, he was surprised by her response.

"Oh, no, he's not been isolating himself the way he does, didn't you know? He's had that nice Molly Hooper over several times." She nodded up the stairs, eyes twinkling as she added, "She's there now, matter of fact, but I don't think you should interrupt them dear." She was smiling broadly, and John's brow crinkled in confusion. "I just heard him telling her he wanted to oil her lenses, and then she said something about cleaning his pipette and, oh, the giggle she gave!"

John hated to be the one to burst Mrs. Hudson's romantic bubble – especially since he was relieved that she'd finally got it into her head that he and Sherlock were not and had never been a 'thing' – but it had to be done. "Sorry, Mrs. H," he said gently, "but those are actual, legitimate laboratory terms. I'm sure Molly giggled because she felt like she'd made a sexual innuendo, but I think we both know those tend to go right over Sherlock's head."

Mrs. Hudson gave him a doubtful look. "Hmm, I don't know, John," she began, but he kissed her on the cheek again and grinned at her. "Tell you what, why don't I just pop up and see whatever it is they're working on? And if it's anything messy, I'm sure Molly will make sure Sherlock cleans up afterwards!"

Without giving her a chance to say anything more, John bounded up the steps two at a time. Reaching the hall, he pushed open the door to Sherlock's flat and glanced toward the kitchen, where he fully expected to find both his best friend and Molly Hooper be-goggled and nitrile-gloved, standing over a few beakers of bubbling liquids or reviewing slides under the microscope.

However, much to John's puzzlement, the kitchen was empty. He whipped his head around as he heard Molly's voice, very husky (bedroom voice, his mind whispered apropos of nothing) saying:
"Well, Sherlock? I thought you were going to oil my slides."

His eyes wide, rooted to the spot in shock, John then heard Sherlock give a deep chuckle before saying in his deepest, richest, smoothest voice, "Why Doctor Hooper, only if you keep your promise to clean my pipette after, hmm?"

The distinct sound of someone's mouth landing on someone's private parts (his frozen mind, thankfully, refused to conjure up exactly whose mouth on which private parts) caused John's feet to unstick; he spun around, bolted out the door without closing it, and dashed down the stairs even faster than he'd gone up them. Rushing past Mrs. Hudson, he muttered, "Um, yeah, so it's NOT an experiment, enjoy your night out, sorry, gotta go!"

As his feet hit the pavement, he heard his former landlady call out in an exasperated voice: "Well, I could have told you that, John, if you'd have let me explain about the headboard noises!"