Sherlock had noticed right away. Of course he had, it was his job to do so. His movements did not falter, however. Despite his, now fairly intrigued, observer, Sherlock made no reaction and simply went about his experiment.

Well, I say experiment.

His hands continued their course, delicate fingers padding lightly across his exposed torso. This form of stimulus wasn't necessarily something this body was accustomed to, for he had never once touched himself—never needed to; he had deleted the urge. But the case had a need for it. For what was quite possibly the first time, Sherlock had been incapable of grasping motive and understanding the culprit. What deductions could be made on an individual whom Sherlock's mind couldn't grasp? Well, many could be made, he'd argue, but not as many as he'd like.

Now, the subject of sex offenders was an area that Sherlock had already stored plenty of information on. But this particular case had him perplexed. Wrapping his elite mind around it was becoming an exhausting task. It wasn't a particularly pleasant feeling.

So what better way to become well learned in a subject than get hands on experience? Pun intended or not, you decide.

He had started out a bit hesitantly, awkwardly, not knowing entirely what to do despite the pictures and videos he had stumbled upon whilst rummaging through John's laptop when he was bored. He closed his eyes and tried his best to poke around his mind's palace for whatever useful information was there. His hands started on his chest and neck, massaging and groping; his fingers gliding along his jaw line.

Despite his efforts thus far, Sherlock felt nothing.

Mental images.

He had to produce mental images in these circumstances to provide maximum arousal. But what could be imagine? Sherlock hissed at the lack of knowledge.

If he could just focus on something. Anything. As he wracked his brain, his fingers busied themselves on his shirt's buttons. Slowly he unbuttoned them, each button like a door opening in his…studies.

'Brainy is the new sexy.' Top few buttons opened.

'Let's have dinner.' Bottom buttons opened; hands pressing cold against his bare chest.

'I'd have you, right here, on thi—'

The woman's voice echoed in his mind, adding subtly to what Sherlock deduced might be arousal. He breathed a sigh out his nose and pressed his hands against his torso as he guided them lower.

This is when he noticed.

As if the creeks in the house weren't a dead giveaway. Obviously, John had come home early from his shift at the clinic. And he was half way up the stairs; frozen in his tracks. No doubt because of the sight his eyes now bore into. Sherlock opened his eyes and gazed at his flat mate. His look went unnoticed judging by John's expression.

Not skipping a beat, Sherlock let his hands massage his body. However, something had change. It was subtle, yes, but whom better than Sherlock to notice the difference? His breathing hitched a bit, and his pulse elevated.

This was quite unexpected.

Sherlock felt his hands tremble and he quickly shot his eyes towards John. His stomach dropped as he observed his observer. Lips wet, obviously just licked, brow wrinkled, eyes wide and unmoving.

Whatever this was doing for John, it so happened to do…for Sherlock as well. And Sherlock was not going to let the opportunity pass on data collection. Or so he'll regard it as if ever asked about it in the future.

Sherlock breathed another heavy sigh as he unbuckled his belt. Jittery hands fumbled with his fly but they succeeded. Even someone as unpracticed as Sherlock understood the basics. However, he had not considered this particular scenario.

His underwear was tented ever so slightly, which was a new sensation, he'd admit to that. Bringing a now slightly more steady hand to his groin, Sherlock pressed against himself. Cupping himself delicately, he massaged and rubbed—he had read this was the proper technique. Of course, he hadn't really expected…

"Oh." He gasped, throwing his head back unwillingly. Sherlock pressed over and over, rubbing the dampening fabric, a bit more aggressively than he had originally intended. His breathing grew heavy as he curled his toes. An odd reaction—he'd have to note about it later.

What happened next, Sherlock could never really grasp. Which, again, angered him.

His brilliant mind could never let him unnoticed John who was still hovering in the shadows of the stairs. Sherlock, begrudgingly, could not will his hand to stop as he gazed again over at his flatmate and quickly closed his eyes.

It was for only a fraction of a second, but that's all he really needs most of the time. Sherlock's spine shivered as his quick glance marked John fumbling with his belt, pulling it open a bit clumsily. His acute hearing heard the small clink of the metal components of the belt shift. And as if his hand no longer belonged to himself, Sherlock quickened his pace.

Placing his thumbs on the edge of his trousers and pants, Sherlock pulled the fabric layers down to expose whatever dignity he had left. It was a pretty impressive dignity, if you know what I mean.

Sherlock sighed unevenly, his breath hitching once again, as he looked down at himself. For the first time in his life, he actually felt quite…virginal. He had brought himself to this point thus far, and now he was starting to feel a bit shy.

He swallowed nervously, but showed no other sign that he was still obnoxiously aware of John. Moments seemed liked years.

Biting his lip a tad, Sherlock placed the pads of his fingers on the tip; his middle finger grazing over the slit. The feeling was foreign, odd, and Sherlock didn't know how to really compute it.

That's when he hesitated. Maybe it was time to stop. He hadn't read about how long things like this were supposed to go. Perhaps he had taken a wrong turn. John might have ruined the whole experiment.

It was supposed to be an individual study. And now it had gone on quite a bit farther than he intended. It was….this wasn't…

Sherlock, ever so slyly, blinked towards John.

"Oh God…" Sherlock whispered, almost whined, and closed his eyes tightly and pressed his chin into his chest.

John was fully exposed, touching himself; his eyes still dead set on Sherlock.

Immediately, the virgin wrapped his fingers around his cock; thumbing over the wet tip. He hummed a bit as he moved his hand up and down the shaft; his expression not really knowing what to do. His brows furrowed and relaxed; closed eyes tightening and loosening. His posture slumped a bit into the chair, and he leaned over a bit. Sherlock opened his mouth, first wide, then not as much, all in silent gasps and moans. He recognized just how ridiculous he probably looked, but none of that truly mattered. Not now anyway.

His heart raced as he continued on. His stomach dropping every time he let his mind wander back to the well-known fact of what John was doing on the stair case.

Sherlock could now hear him, it was faint, but no sound was necessarily faint to him. He felt hot, sweat beaded on his forehead and his body trembled. The pleasure shook him and he couldn't stop if he tried. His hand moved faster and faster as his ears keenly listened to John's small moans from the stair case.

Sherlock whimpered; the want and need was growing to an intolerable amount. He breathed through his mouth and shot his head back once again.

"Come on…" he moaned, "Oh God, please…"

He would, of course, kick himself later for his unintelligent words.

But he needed the verbal boost. And apparently John did too. For he now heard him all too clearly. The wet noises, the moans escaping through bit lips, and the undeniable whisper of "Sherlock."

That set Sherlock over the edge. He came hard onto his lap, his body shaking. He left his hand moving, riding out the waves of his orgasm—whimpering the whole time. Sherlock let his arms drop to the sides of the chair as he laid his head back and stared at the ceiling. His chest heaved up and down, sweat causing his shirt to cling to odd spots on his chest. Through his breathing he heard John come. It was quite, compressed and then there was silence.

Sherlock pulled his pants back over himself and sat upright. He sat for a few moments, letting his breath continue on to its normal pace. He kept his eyes forward, conveniently keeping away from the doorway towards the stairs. Leaning over and placing his palms together, Sherlock pressed his fingers to his lips and thought.

'Stimulation through fabric layers.' His eyes widened at the epiphany, 'that's the fixation. The offender gets off on the sensation on his genitalia THROUGH the fabric.'

"Obvious." He scoffed at himself for being so idiotic for not deducing that earlier. Sherlock stood up, fastened his trousers and belt, and walked over to John's laptop and updated the site. He then made his way into the kitchen.

Sherlock paid no immediate attention to the amount of time that passed before he heard John walk up the stairs and enter the room (it was 15 minutes). His footsteps were heavier than they needed to be, probably making a point that he was just now getting in. Sherlock was in the process of dropping chemical into a solution when John walked into the kitchen. It was almost enjoyable to observe his body language. Sherlock always thought it humorous, John's overcompensation for uncomfortable situations—or at least he deduced that John is probably in an uncomfortable situation. His composure was too uptight, well more uptight than usual. Sherlock on the other hand…was Sherlock.

John paused for a moment, opening his mouth ever so slightly, but said nothing. Before too much time passed, he went to the fridge and made a good point of opening it wide and staring into the bright light that now flooded the dimly lit kitchen.

The detective glanced for a mere second at his flatmate's back (noticing all the tidbits such as his hair being tossed because of the pacing he obviously did downstairs while running his hands through it). He averted it just before John turned on his heel to face him. He used an eye dropper to add the chemicals carefully into the solution.

"No food." John stated.

"Good observation."

"I'll get the shopping done tomorrow."

"Fine."

There was a pause.

"It was a late one tonight. Just getting in now, so…"

Sherlock looked up through his goggles, and then back down at his work.

"Goodnight, then."

"Yes, fine."

And with that, John left Sherlock in the kitchen to finish his work.

When Sherlock heard John lock his door, he heard a much muffled and much held back cuss.

A small tug at the corner of his lips brought Sherlock into a smirk, and his last drop of chemical fizzled.