Author's Notes: This was my fifth attempt at the prompt I was given—which was, essentially, for any kind of swapfic—for the 221b_slash_fest holiday exchange. This was beta'd by the magnificent moony, and Britpicked by the marvelous melaszka.
There was a long pause before the man in question found his voice. "Ah."
The thing was, it was John. It was definitely John Watson who had wandered downstairs, hair messed up from sleep, wearing striped pyjamas, bare feet shuffling along the creaking wooden floor. It was a typical sight on a typical morning, one that greeted Sherlock more often than not. Nothing unusual about that at all.
Only, this was not John Watson, because the person currently staring at him through atypically—for this hour of the morning, at least—sharp blue eyes couldn't be John Watson. The voice was wrong, for one thing—rather more mezzo-soprano than tenor.
Further, this person was missing certain characteristics that John Watson possessed, like an Adam's apple. And a penis.
There was also the matter of the breasts.
"I don't suppose you can explain to me how this happened," John said, with the sort of forced-casual tone typically used when there were dead snakes in the bathtub or an assortment of ears laid out on the kitchen table (in the name of science, of course). As if on auto-pilot, John reached for the kettle and filled it with water while determinedly keeping his hands steady. Or her hands, Sherlock supposed, if one were concerned with pronoun accuracy. And Sherlock was always concerned with accuracy.
Of course, he couldn't help but stare. It was fascinating to watch John breathe in and out like he always did, only now—with the addition of mammary glands—it was a completely new experience.
"Don't look at me like that," John said, without even turning his—her—head.
"Like what?" Sherlock asked, curious.
"Like I'm an experiment," John said, turning to face Sherlock and crossing his—her—arms over her chest.
Sherlock stared, transfixed.
"Sherlock," John snapped irritably. She put her hands on her hips and glared at him.
"Hmm?" Sherlock asked, glancing up at John's face.
"I asked you—"
"Oh, I heard you," Sherlock interrupted, waving a hand dismissively. "And you should take off your pyjama top," he said after a moment of thought, crossing the kitchen in two strides to stand before John. He reached down for the hem of the top and began tugging upwards on it while John stared at him, stunned.
"What? No!" John exclaimed, slapping his hands away indignantly and taking a step back. "What are you doing? What the bloody hell is that supposed to accomplish?"
"Quite a lot, I should think." Sherlock reached forward again and tugged upward. "Off," he demanded.
"Sherlock—!" John spluttered, her arms getting tangled up in the top as Sherlock insistently pulled upward.
"Oh, please, John," Sherlock said impatiently as he managed to yank the top up and over John's head, exposing her chest. "It's nothing I haven't seen before."
"It bloody well is!" John protested, arms automatically crossing to cover her chest as she glared up at him. "I've never been a woman before this morning!"
"And I've seen your chest plenty of times, just because you have a little extra—"
"Don't you dare finish that sentence," John said, voice low—well, relatively speaking, given the higher register she was currently working with—and deadly.
Sherlock reached for John's arms and attempted to prise them apart. "No matter. You knew what I was going to say, anyway."
"Why are you trying to ogle my…" John squirmed as best as she was able while keeping her arms clamped around her chest.
"New data is always worthy of study," he said, distractedly, as most of his attention was on getting the proper leverage to move her arms out of the way. He couldn't conclusively say why he felt the need to see, but the fact that he had the urge at all merited investigation.
"What did I just say about—"
"Don't you want to know how and why this happened?" Sherlock asked, keeping his hands wrapped around her wrists even as he stopped fighting her for the time being.
"Yes, of course," John sighed in relief, sagging a bit against the worktop behind her.
"Then would you really deny me the opportunity of examining potentially crucial evidence?" he asked, his eyes boring intently into hers.
John merely raised an eyebrow. "On my chest?" Her tone was as dry as the Sahara.
"Yes," Sherlock said simply, holding eye contact with her, confident that she would—as per usual—let him have his way.
And, as usual, she did. "You're going to want me to get completely naked, aren't you?" she asked, resigned.
"Evidence," he responded smugly as he released her wrists and stepped back, eying her expectantly. John sighed, but it was a well-practised and familiar sound.
John raised her eyes to the ceiling, and then shook her head and undressed clumsily. John's body had suddenly gone from a well-travelled trail to a blank expanse full of mystery and surprise. Sherlock felt his heartbeat speed up.
"I thought you weren't interested in women," John said tartly as she removed underwear that bagged and sagged in all the wrong places on her.
"I'm not." He paused briefly. "Though I've always been interested in you."
"I think that may have been the most romantic thing you've ever said to me," John said thoughtfully after a moment, as though unsure whether to be touched or amused.
Sherlock didn't answer right away, preoccupied, as his eyes roved over her body. The scar that he was intimately familiar with—one of his favourite landmarks on John's body—was still there and looked the same, puckered and unnaturally pale. His eyes traced a waist that curved in and hips that flared out more dramatically than he was used to. Subtle changes, perhaps, but to an eye as practised as his—both in anatomy in general and John's anatomy in particular—they were glaringly obvious. Sherlock catalogued it all: bone structure slightly more delicate, less body hair—both in terms of thickness and in sheer quantity—an abdomen that was softer and fuller than the corded muscles and taut flatness that Sherlock was accustomed to.
Carefully, he reached a long, thin finger towards John and ran it lightly over the areola of her right nipple. John gasped loudly and Sherlock catalogued the reaction. Clearly, she was much more sensitive there now than before.
"Hmm, interesting," he said, and it was. He'd always loved new puzzles, and testing and exploring John's body all over again was quite a tempting one. He traced her ribs with his finger and she shivered in a delicious way, a strangled sound that was part protest and part demand for more.
Yes, this was going to require some in-depth study and analysis.
He grabbed her hand and tugged her towards the bedroom.
"Sher—what—what are you—what about working out how—"
"Later," Sherlock said, leading her into the bedroom and pushing her down on the bed as he began to undress.
"What do you mean, 'later'?" John demanded, staring in surprise and, if Sherlock was any judge—and he was—lust.
Sherlock rolled his eyes as he unbuttoned his shirt. "Oh, John, isn't it obvious? This is clearly a rather pathetic attempt by Moriarty to drive a wedge between us." He dropped his shirt on the floor and unbuttoned and unzipped the fly on his trousers.
John's blue eyes went large with equal parts consternation and amazement. "How on earth can you possibly know that?"
"He seems to think that you being a woman now will put me off," Sherlock answered, efficiently stripping off his trousers and pants in one go. "It's so feeble as to be laughable, but it has provided us with an extraordinary opportunity."
He knelt next to the bed and pulled John to the edge by her legs, settling himself in between them. He rubbed the outside of her knees as they bracketed his head, taking note of John's increased colour as well as her accelerated breathing. Interesting.
"It has?" she asked, sounding dazed and, Sherlock was pleased to discern, eager.
"Obviously." His fingers trailed up the outside of her thighs, and he carefully logged the trembling and twitching of her muscles. He'd never known that area to be particularly sensitive before. Yet another difference.
"I suppose if it's for science," she said, breathlessly, as he nuzzled his nose along the soft skin near her right knee.
"It is," he answered and was pleased to feel her tremble. He began kissing along the inside of her thigh.
"And I eventually get turned ba—" John broke off, gasping again, and Sherlock was fascinated by her voice.
"You will," he promised. He then leaned forward, noting the differences in scent and texture and sight. Time to begin.
"Oh, God, Sherlock!"
Yes, Sherlock thought. This is going to be an extraordinary experiment.