Molly was starting to nod over the last of her paperwork when he strode into the lab, long coat flowing, a few snowflakes still caught in his dark hair.

"Sherlock," Molly said, suddenly wide awake. "How did you get in? The department has been closed for hours. Everyone has gone home."

Sherlock's eyes cast quickly down the length of the empty room and back to the pathologist. "A few locked doors and a couple of alarms do not signify, Molly. Surely you know that by now."

Molly pursed her lips, pleased in spite of herself that the detective (her detective, as she sometimes dared to think of him) had circumvented security to come and see her. He'd only just got out of hospital after being shot, and it was lovely to see him dashing around again.

"I suppose you won't tell me how you got in?" Molly asked, trying to be stern with him but feeling a smile creep onto her face.

"You suppose correctly," he said in his commanding baritone. "Molly, I need your help with an experiment. Now."

"Oh." Molly put down her pen, but then thought of how furious her boss would be if he found out that she had once more broken the longstanding "no Sherlock Holmes after hours" rule. She had to put him off, but how?

"I, um, I cleared away all my equipment already, so-"

"Not a problem," Sherlock cut in, smiling tightly. "The experiment I have in mind is psychosocial in nature."

Mystified, Molly slid off the tall chair. "Psychosocial. Not exactly up your street, is it, that sort of thing?"

"I gather the data I need, when I need it. Now clear a space on the counter, about a meter square." A directive, not a request. "Wherever's most convenient," he added generously, keeping his own hands in his pockets.

Molly blinked once, then started clearing away part of the long lab counter. Well, imperious as always. She really should mind it more than she did.

As she set down the last beaker, Sherlock continued, "I need you for this experiment, Molly. A case study, really. I want to make a few observations with you as my subject."

"Me?"

"Yes. You." His ice-blue gaze focused in on her, and Molly knew he was cataloguing every reflexive tensing of her muscles, every nervous intake of breath. Molly felt herself pinned under the force of Sherlock's eyes, and knew that his experiment had already begun.

Casually, with one foot, Sherlock pushed a stepstool a few inches over so that it was right in front of the cleared area. "Remove your shoes and your lab coat, step onto the first step, and face the counter," he said.

More orders. Well, all right, Molly told herself. It was far from the weirdest thing he had ever required from her. She smiled as she remembered his casual inquiry after an edentate head and a left forearm with a recently healed compound radial fracture, both from the same cadaver. Whatever he had in mind couldn't possibly compare.

Molly toed off her sensible shoes, laid aside her lab coat, and stepped onto the stepstool in her stocking feet. Sherlock was watching her closely, his eyes raking down her body. She felt a blush spreading up her neck, and knew that he must be noting it.

"Yes, that will work. Now, bend over onto the countertop."

"Sherlock, what…" Molly turned curiously. Distractedly, she noticed that he was still just a little taller than her, despite the stepstool.

"Face down, on the counter, Molly. I need data." His voice grew softer, deeper, almost tender. "I need to observe your reactions. Will you help me, Molly? Please."

Molly couldn't resist that voice. She obeyed him, bending over the counter and resting her head on her arms. It was not uncomfortable; the stepstool placed the hinge of her hips precisely at the counter's edge. "And I suppose someone's life depends on this data? Somehow?" she asked, her voice squeaking just a bit.

She heard Sherlock chuckle behind her.

Moments passed. Molly listened, but the lab around her was silent. It seemed that Sherlock was simply standing still, observing. Perhaps this-whatever it was-was all he wanted?

But Sherlock spoke into the silence.

"Molly. Raise your skirt."

A pause. She could not see his face, but she could feel his gaze like a weight on her body.

"Sherlock." Molly spoke urgently. "What are you doing? Why-why do you want me to do this?" She was…not afraid, precisely…but her body was aglow with the strangeness of her position, such a vulnerable position, and of him looming so close behind her.

"Do you trust me, Molly?"

"I...yes."

She felt the rustle of his coat on one side of her body as he bent over her. His face came into view, inches from hers.

"Molly, I want you to know that you are safe with me, always. I will do nothing to harm you. You will help me be the judge of that."

Her body thrilled to his nearness, the faint scent of his hair, and the feel of his hand resting lightly on the small of her back.

"I will stop everything and draw away from you immediately whenever you say the word 'skull.' Anytime you like." He watched her face carefully. "I may also require the word from you, and then I will stop if you fail to say it. Say 'skull' now, Molly."

"Skull," she replied, steadily holding his eyes.

"Again."

"Skull," she said, a little louder. He would stop "everything" if she said this word?

His eyes crinkled with pleasure. "Good girl." His face disappeared, and she felt him stand upright, still behind her, his gloved hand always on the small of her back.

"So, now, raise your skirt. This too is necessary."

A deep breath, and another. Yes, she trusted him. Molly drew her hands down to her waist and pulled her skirt up over her bottom. Sherlock's hand lifted for a moment, tucking the excess fabric underneath her and then returning, possessively, to the small of her back.

"Now lower your tights…and take down your pants with them. "

Her blood thundered in her ears.

Molly took a breath, and reminded herself that she really was safe, that she could always say "skull" anytime she pleased, and always trust Sherlock to respect it. And she realized something more. With a molten rush of heat to her face, she knew that she wanted to obey him. That she burned to show Sherlock, beautiful brilliant Sherlock, her bare bottom.

As if in a dream, she slowly, slowly pulled her final layers down over her arse, her face blazing hot against the cool countertop, legs trembling.

Molly felt Sherlock's hand move on her back, just a fraction of an inch. Surely he was now inspecting her white bum and pink folds. She tried to keep her bottom lifted high for him, knowing there was no hiding from his gaze. No need to be Sherlock Holmes to see how aroused she had become. Never in her life had she been so excited, not even that time at uni when her boyfriend had tied her to his bed and…

"Ah," Sherlock said, his voice somehow different. "Beautiful, Molly. You're doing beautifully. See if you can reach your arms up and hold onto the other side of the counter. Yes, well done."

The hand at the small of her back moved downward. His gloved fingers cupped her right buttock, then her left. His large hand spanned her arse, pressing her cheeks together. Molly could not help it; she heard herself making a faint keening sound as his hand moved her bum from side to side, experimentally.

"Lovely, Molly. And...what's this?...So...very...wet."

Molly couldn't help herself; she moaned softly. With those words, Sherlock had brought into the open air the undeniable carnality of his experiment. As if stepping outside herself, Molly saw the scene: the slight woman bent over the counter with her pants around her thighs, the tall man just behind her, icy eyes focused on her naked bottom. The image shimmered in the lights behind Molly's eyes.

Inexorably, Sherlock's thumb moved into the cleft between her buttocks.

"So exquisitely wet, Molly. Like a pink rose dipped in oil...and look, a sweet pink rosebud to match," he said, his thumb tugging at the skin a scant inch to the side of her tiniest opening.

Molly shivered. No one had yet touched her there.

"And so sensitive. Yes."

Sherlock's hand drew away. Molly whimpered, bereft.

"Quiet," he snapped, making Molly jump. "I'm removing my gloves now. There," he said, his voice gentle once more, and she felt his hand again, now sliding almost chastely down her hip. His bare skin against hers. "That's better, isn't it." She felt his other hand now, soothing, as he slowly stroked her white arse and thighs.

"So lovely, Molly. And you're being so brave, so brave for me." His fingers quested. "This experiment is an important one. Precise observations are crucial to my inquiry. What would I observe, I wonder, if I touched you…here?"

And Sherlock's cool, clever fingers slowly stroked into the hot folds of her cunt.

"Oh. Ah ha. Ah ha ha!" Molly was astounded to hear herself laughing as pleasure seared her.

From the moment Sherlock had directed her to bend over the counter, her body had warmed to his orders, his domineering voice, his aura of power. Molly Hooper was a professional woman, a fully qualified doctor, a noted researcher in her field. But even so, here, tonight, she was squirming on a lab counter as Sherlock took her unprotesting body firmly in hand.

Sherlock slipped a finger deep into her body. And another. Helplessly, Molly lifted her hips, silently begging for more fullness, more pressure. Sherlock teased her instead, drawing his fingers out and swirling two fingertips around her swollen bud.

"Classic female sexual response. Vasocongestion and blushing of the vulva. Lengthening of the vaginal canal. Clitoris slips out of hiding. Lubrication…such a quantity, Molly. Any interest in saying your word? I thought not." He cupped her cunt with his whole hand, wicked fingers still rolling over her most sensitive area.

"Lift up that pretty behind for me. Higher."

Deliriously, Molly obeyed. What else was there?

Moments passed, and Molly felt his other hand roaming over her arse, his hand between her legs never still. Sherlock was stroking her with undeniable skill, observing her responses, noting the touches that made her squirm and sigh. Time slowed, and Molly's whole world narrowed in on the coolness of the countertop under her breasts, the faint sounds of Sherlock's exhalations behind her, the molten pleasure in her cunt.

Finally, she felt Sherlock leaning over her, pinning her body to the countertop.

"You like being under me, little Molly? Give me your word or I'll stop."

"Skull!" Molly cried. "Oh god, Sherlock…"

The fabric of his coat covered them both-his clothed erection almost painful against her hip-a gathering tightness deep in her belly, a warning-

"Come for me, Molly. Yes. There we are," Sherlock said, as Molly turned her head and screamed into her arm. Helpless, she rode out the sharp ripples of her orgasm, trapped under the delicious weight of Sherlock's body.

"Oh, good girl. My good girl," he said, rather breathlessly, caressing her soft arse, her hip. She felt him rest his head on her shoulder.

Molly shifted under him, slowly coming back to herself. Sherlock was supporting his own weight now, but was still arched over her. His hand cradled her pussy, shielding her warm wetness from the chilly air of the lab.

Molly's mind drifted. She knew she ought to be feeling...something...but just couldn't be bothered at the moment. Molly let her eyes close, and relaxed. She and Sherlock breathed together.

After long minutes, she felt him stir, pushing off her, his hand finally coming away. She turned her head, catching a white flash of fabric out of the corner of her eye just as he said, "No. Eyes forward." His voice was cool and even again.

Molly obeyed, puzzled, her gaze wandering across the counter and over grey cabinets, cold glassware.

"Thank you, Molly," Sherlock said. "We shall talk...later."

She felt him step back, drawing away from her, and confusion arose like a fog. She tried to obey him and keep her eyes forward, but as she heard more footsteps, she gave in to curiosity and furtively peeked to the side. She saw Sherlock from the back as he walked calmly away, wiping his hand on the white handkerchief and whipping it back into his pocket. Molly's confusion deepened as she watched Sherlock open the door, keeping his face turned away, and leave the lab.

Molly collapsed bonelessly back onto the counter, oddly relieved, her body and mind suddenly heavy with fatigue. After a time, she reached back to pull up her pants.

An hour later, just as Molly was about to slip into a candlelit bath to enjoy the silky water and process the events of the evening, she heard her phone chime.

I trust you got safely home.
SH

Molly smiled with one corner of her mouth.

Yes I did.

Molly paused, then sent another reply.

So, you really have to tell me. What was that experiment all about?

If you care to continue, come to Baker Street tomorrow, 16:00. Wear a skirt.