A knock on the door made her jump. She went to call out, but of course he, impatient as he was, came straight in, coat flapping behind him. Never mind the fact that she was in her underwear, he sat himself neatly on her bed and patted the spot beside him.

'Come and sit down,' he demanded.

'Just let me put something on' she hurried into her bathroom and threw on her silk dressing gown, before perching herself on the bed next to him. 'What do you want, Sherlock?'

'Must you assume that I want something?'

'Well you do, don't you? Why else would you be so desperate to talk to me.'

'Good point.' he acquiesced. 'I was wondering if you would be willing to take part in a little experiment for me?'

'What is this experiment?' she enquired.

'Yes. I was just getting to that,' he replied irritably. 'It has come to my attention that there is an area in which I always fail to understand people's actions due to my ignorance of the subject.'

'Is this about the fact that you didn't know the earth goes round the sun?'

'Why must everyone bring that up all the time? And stop interrupting. No, this is about something else. I need to understand why people are consistently motivated by passion...' then he added in an undertone '...and lust.'

She stared at him in blank incomprehension. Surely he didn't mean what she thought he meant...

'Do I have to spell everything out for you?'

She nodded meekly.

'I need to understand how sex and passion could drive someone to commit crime.'

'Gonna need more info than that Sherlock.'

With his typical bluntness, 'I need you to have sex with me.'

'So you immediately thought of me? How very flattering!' she exclaimed, although in her mind, the fantasies she had dreamed up, knowing they couldn't happen, were flashing through her mind. His long-fingered, violinists hands caressing her, the way his dark, curly hair would brush against her skin, the way he... She blushed and realised he was waiting for an answer.

'But why? I assumed you and John..?'

'We're not a couple.'

'Oh.'

A moment of silence as tension lingered like a whiff of perfume in the heady air.

'Yes,' she whispered so quietly Sherlock heard it as a caress.

He reached out and touched her hand and a shiver of anticipation ran through her. Though his only motivation was to better understand the human condition, she was dong it merely for her own selfish pleasure. Excuses like its kindness to a friend, I'll save lives by helping him understand powerful motivators were meaningless. She wanted him, and had since the moment she'd first seen him.

...

Rain. That's all it ever seemed to do in England. Why she had thought it a good idea to take a year out to study abroad she did not know. She missed the sunshine of France.

'Excuse me,' she asked someone walking in the opposite direction, trying to hide the faint traces of accent she'd worked tirelessly to disguise. If one was serious about speaking a foreign language they should do it properly.

'If you had stolen something and didn't want anyone to find it, where would you hide it?' the man addressed her. He was striking in a way few men were. Pale skin, ice blue eyes and dark curly hair. And those cheekbones! Wait! He'd asked her something.

Trying to regain her composure she'd replied with 'The obvious place where no one would look.'

He'd looked almost disappointed, then she watched as several emotions flitted across his face incredibly rapidly. Surprise, consideration, shock and finally triumph were displayed vigorously. She wondered what... No! She restrained her thoughts from straying and looked up to find he was gone.

She'd got herself the job at Speedy's several weeks later and became fast friends with the woman living next door, Mrs. Hudson, who treated her like her own daughter after finding out she knew no one in London. She often popped over to Mrs. Hudson's for a cup of tea after work and enjoyed hearing stories about the eccentric detective who lived upstairs. She'd finally met him and had been in shock to realise it was cheekbone man, as she'd been calling him in her head.

...

She pulled him towards her and brought her lips to his mouth. He was surprised at first before responding in turn and kissing her back. He felt her smile as she leant her head into the kiss, seizing the chance of his opened mouth to push her tongue in and entangle them together.

She let out an involuntary moan when he brought his hands up to cup her face as she reached round to tangle hers into his mess of black curls. She brought her hands down to tug at his coat. He took the hint and pulled it off before bringing his hands under the flimsy silk of her dressing gown and resting them on her hips.

He was pushed down onto the bed as she straddled him and untied her dressing gown before discarding it to the side. His face showed no reaction to the fact that she was now before him clad only in a skimpy bra and pair of knickers, but his body betrayed him.

She ignored the feel of him pressing into her thigh and began to unbutton his shirt, peppering his throat, and collarbone, and chest, and stomach with hundreds of kisses before throwing his shirt onto the ever increasing pile of their discarded clothes.

His hands had not moved from her hips so she leant and whispered in his ear.

'Touch me.'

She reached round and unclipped her bra before placing his hands on her breasts. She whimpered at the feel of his cold touch on the sensitive skin and this seemed to be all the encouragement he needed. He rolled over, pinning her beneath him. She should have known he would have wanted to be the dominant one. She sucked air in as he began to massage first one breast, then the other.

Sherlock was back in control, just how he liked to be. The noises she was making were incredible. She moaned and he felt that previously unexplored area of his anatomy (except from in his hormonal teenage years, obviously) react just to the sound.

He continued to massage her breasts, then remembering how it felt when she'd kissed places other than his mouth, leant in and began to kiss down the hollow of her throat before moving along her collarbone and down to the curve of her breast. The closer he got to her nipple, the more intense the noises she made. She reached out and fisted her hands in his hair as Sherlock took a nipple into his mouth and began to suck.

'Sherlock!' she gasped. The things he was doing to her.

He suddenly found himself back down on the bed with her flushed face over him. At some point during his ministrations her hair had come loose from its clip and fell around her face like a dark waterfall.

'I was meant to be teaching you, Mr. Holmes.' she purred. He was happy to comply.

'Too... Many... clothes,' she managed to say in between kisses as she reached down to undo his belt. He was glad, as he was beginning to find his trousers ever so slightly uncomfortable. And then her small hand brushed against the point in his trousers where the pressure was greatest and he groaned.

She pulled his trousers off, followed by his boxers and was greeted by the sight of his manhood, proud and erect. She'd seen some before but his was by far the most impressive. Thick and long, she was dizzy with anticipation at the thought of it inside her.

He shuddered and let out a loud moan when she wrapped her small hand around his length and began to run it up and down his shaft. He had to grasp onto the pillows when she brought her mouth down to lick up the side before taking it into her mouth. The sensations racking his body were like his nicotine highs but a thousand times stronger. He realised that her mouth was no longer on his penis but before he made any move she was kissing him again, more forcefully than before, and he answered with as much force. He once more gained the upper hand as he flipped her onto her back.

He realised she was still wearing a pair of black lacy knickers so he reached down, before reconsidering and grasping the material between his teeth and dragging it down her smooth legs. The flimsy material was sodden and he didn't need to question why. Though he had no idea of the sensations of sex, he did know the mechanics of it.

He began to kiss back up her legs. Along the instep and ankle, along the toned length of her calf and over the knee and up her inner thigh. He could feel the heat from her core and began kissing closer to the dark patch of curls at the apex of her legs. She let out an incredible moan with his name in it, which only encouraged him further. He kissed higher and higher before reaching the juncture, where he proceeded to kiss, and lick, and suck. He listened to her reaction and soon she was panting as her head rolled backwards to let out a breathy moan.

She surprised him by reaching down and pulling him up to her.

'Found any clues, detective?' she purred into his ear.

'A few.' he was surprised at the huskiness of his voice. 'I still have a few more places to look, though.'

The last word of this pronouncement was never heard as she kissed him gently, asking for permission to introduce her tongue this time, rather than just forcing in. He was happy to oblige.

He felt her hand grasp his shaft again, but before he could disentangle himself from the kiss he felt himself guided into her incredibly wet and tight core.

For a moment he remained still, revelling in the feel of her heat surrounding him before she encouraged him further by pushing her hips up to his causing delicious friction that made him moan louder and more deeply than he had before. She hooked her legs behind his hips as he settled his hands on either side of her body and she encouraged him to thrust, first slowly and gently, but then picking up the pace and force. He leant forward and buried his head in the curve of her neck as he felt the unbelievable sensations rack his body.

She was panting and moaning and saying his name as she felt him hit a spot deep inside of her that caused her almost unbearable pleasure. She let out a little scream as he hit it again and again.

'So good.' she whimpered.

He pulled back almost all the way out of her and she reached out with her arms, trying to pull him back, searching for the unbelievable feelings he was giving her.

Sherlock was biding his time and leaning his head down to kiss her thoroughly his hand ghosted up the side of her body to her breast where he began to knead and squeeze until she was entirely at his mercy. She yelped as he bit down gently on her neck, enough to leave a mark, and a bruise in the morning.

Just as she had gotten used to the lack of movement within her, he slammed back into her, sending her into almost unimaginable height of pleasure. He repeated his actions as he felt her encompass him again and again. he began to feel his control slipping and welcomed it. He could feel something building in the pit of his stomach. Then she cried out louder than ever and he felt her tighten around him, if that was even possible. Her tightening caused him to fall over the edge into his climax and he felt the world spin away from him as he cried out in wonder. He saw stars before his eyes as every muscle in his body came alive. He saw things more clearly than ever as he fell limply onto the bed beside her spent body. Every part of him had been working in harmony as he reached for that incredible high.

He'd had no idea what it was that had so fascinated the other members of his species with sex before. But now, having experienced it himself, he couldn't believe the freedom it gave, and the pleasure! His mind had been blown, for the first time ever.

'Don't they say that the most reliable data is collected from repeat experiments?' she asked, her voice husky with want.

'Yes. Repeated experiments. And the more you repeat, the more reliable your data.'

'Well then.' She turned over and pinned Sherlock beneath her naked body and leaned in for a passionate kiss. Sherlock could feel his cock harden and eagerly rose up to meet her kiss.

...

John realised that Sherlock Holmes had a new addiction. Whenever he encountered a difficult case, instead of reaching for the nicotine patches, he would disappear for several hours and come back to the flat completely exhausted, but with the answer. He had his suspicions that Mrs. Hudson knew what was going on as he caught her winking at Sherlock. But who was he to interfere with the way Sherlock's brain worked?