Wrote this ages ago but have only just typed it up. It was in response to a comment on tumblr, saying how they wished someone would write a fic where Sherlock had to admit to being a virgin. Enjoy.
John Watson wearily climbed the steps up to his and Sherlock's flat, and stopped dead in the doorway when he saw what his flatmate was doing.
Sherlock Holmes was sat on the sofa in his usual thinking pose, surrounded by pieces of paper and both his and John's laptops. On the pieces of paper were various diagrams and scribbled notes, and on the laptop screens were a few diagrams and some pictures. It was what the pictures were of that stopped John in his tracks. He cleared his throat, and did so again when Sherlock didn't respond.
"I know you're there John, and if you're making tea I'll have some too." John raised his eyebrows, but went into the kitchen to make tea. A few minutes later he returned with two mugs and, after passing Sherlock a mug, sat down in his chair.
"Sherlock, what are you doing?"
"Research for the case, isn't it obvious?"
"A woman was brutally murdered and her body was damaged almost beyond recognition. How does this," John gestured towards the laptops and paper, "have anything to do with that?"
Sherlock sighed. "Of course it does John, weren't you looking?"
John sighed. "Yea, yea – I saw but didn't observe, okay? What was it I didn't observe? She was murdered by her husband, who obviously hated her, for whatever reason."
Sherlock looked up quickly and frowned. "Oh no John, he loved her very much."
John paused, pursing his lips. "What? Sorry, but what?! 'He loved her very much'? That's not how you treat people you love, Sherlock."
"Her heart was missing, John – her heart. Why would somebody kill her, sexually assault her, and cut out her heart (though maybe not in that order)? If he wanted her dead, why not just kill her? And her face – her body was cut and stabbed but her face was undamaged, her eyes closed respectfully. There was obviously a reason and I'd been missing it until now." He gestured towards the laptops and papers.
"Why did you need to research this Sherlock? Surely you knew these things already?" Sherlock looked sheepish and started reading a list of notes from a piece of paper. "You did know, didn't you?" No reply. "How can you not know this stuff? It's basic biology!"
"I know and understand sexual intercourse as a method of reproduction and bonding. I've needed to know very little beyond that, until now."
"So you searched porn on my laptop?"
"Just research; I needed to know."
John sighed. There was a moment's pause before John came to a sudden conclusion.
"But how can you not know this? You'd have to..." John trailed off, as Sherlock continued reading his notes and shifted uncomfortably in his seat. "Sh-sherlock?"
"Hmm?"
"Are you a virgin?"
"Yes John, I am a virgin. Has that satisfied your sexual curiosity for one day?" Sherlock snapped, before looking away, and John could have sworn he looked embarrassed, so he didn't probe further.
"So what does this have to do with the case?"
At that moment the doorbell went, and both men listened as Mrs Hudson let Gregory Lestrade in. He ascended the stairs quickly and entered the flat.
"Go on then Sherlock, you said you'd solved it. Hi John."
John nodded in acknowledgement and waited for Sherlock to explain.
"It's obvious who did it but you can't arrest him because you can't find a motive. Now: it can't be anger because he wouldn't do something like that on the spur of the moment. It can't be jealousy because she was faithful. It can't be secrecy because he has nothing to hide. It can't be money because she had none – not even life insurance. He couldn't have wanted to end the relationship because he would have told her or she would have noticed. So..."
"Sherlock, there's no motives left."
"Well obviously there is because you haven't found the motive yet." He paused, looking at their blank faces. "Come on! Use your imagination!"
Greg frowned, glancing at Sherlock's research. "You can't mean it was a sexual fantasy."
"Oh give the man a medal!" said Sherlock sarcastically as he turned over a page of his notes. "It was something they'd done before – did you see the scars on her body? But only in the places where it would be safe to draw blood. This time he got carried away and before he knew it he'd strangled her: he decided he may as well fulfil his sexual fantasy before leaving and grieving, so he does." Sherlock paused as he closed a few windows on his laptop. "Now Lestrade, you go and arrest him: I can't imagine he'll be hard to catch, though I suggest you charge him with manslaughter rather than murder. And John, a coffee would be nice."
Greg and John glanced at each other before shrugging and moving to do as they were told; no point arguing with Sherlock Holmes.