It really was an extraordinarily hot Summer.

Sherlock didn't let the weather bother him overly: he couldn't control it (although, he was sure a sweating, chubby Mycroft was hell-bent on finding a Way) and there were means of adjusting indoor temperatures to make one more comfortable, after all. And the outdoors, he thought with a sniff, were merely a series of connections between the indoor spaces he inhabited and didn't often require him to tarry on his way between those spaces.

But this Summer was different. He couldn't seem to get comfortable, even with the air conditioning running non-stop in the flat and several pedestal fans blowing enough of the cooled air about that he could huddle up on the sofa in his Belstaff. Much to Mrs Hudson's disgust. He felt more on edge than usual; nerve endings prickling, all synapses firing and his hands working through his hair constantly trying to agitate his scalp in the vague hope of marshalling the errant thoughts into battalions he could deploy to his usual devastating effect.

The problem was not the heat, however, but a by-product of it.

Flesh.

Exposed flesh.

It was everywhere around him.

Young, short-skirted mothers walking hand-in-hand with pre-pubescent short-skirted daughters. Rough sorts who'd abandoned their consideration for public decency with their shirts; pale skin revealed to all and sundry and burned bright red and peeling.

John was getting about in t-shirts and shorts. Shorts.

He'd even caught sight of Mrs Hudson pottering about beyond her open front door – "For better air circulation, dear," – in just a light housecoat and rayon slip.

He could dismiss most of it with a sneer. The teenage girls traipsing about in packs clad in little more than a bikini apiece were viewed as unemotionally as mannequins and the lads ogling and wolf-whistling after them proved interesting only for the seconds it took to deduce whether their visible back or chest tattoos – acquired while drunk, on holidays 'with the boys' – told of wasted nights in Ibiza Town or Kuta.

He'd seen his brother briefly and was unsurprised to see the requisite umbrella in tow, even with the obviously reluctant transition to a taupe linen suit minus waistcoat that Sherlock knew was usually only worn in tropical climes or desert locales that Mycroft absolutely couldn't avoid.

"Really, Brother Mine, doesn't the linen crumple awfully when you're chasing after ice cream vans?" he scoffed, pantomiming brushing out elbow creases he (personally) didn't have.

"Ahem," was the reply, garnished with an unimpressed raised eyebrow.

Mummy, up from the country for Wimbledon and camped out in a cool suite at The Dorchester, lifted her head limply from the back of a divan and rolled her eyes tiredly. "Sherlock," she sighed.

"I suppose I'll have to fetch my own 99s," he smirked unrepentantly.

All of this was more or less tolerable. He could keep his head down traversing the streets in the oppressive heat, not making any concessions except leaving off his jacket and coat, and not being caught out by the spectacle of bared skin by walking into a lamp post – as had John – when a pretty girl revealing more than she covered was larking nearby.

The only thing to give him any trouble, to keep him tossing and turning when he deigned to go to bed or lingering in cold showers, was one particular patch of exposed flesh not more than half a metre square – or, his fevered mind estimated, an area equivalent to 4-6 of his hand spans.

Molly Hooper's back.

Her naked back, as he'd encountered it at St Bart's one night; revealed when she'd been fussing with some unimportant task like inventorying the contents of the lab without the benefit of her white coat.

It had been during a slow patch when the denizens of London, clearly pacified by the sun, weren't murdering each other and thus there'd been time for those often-ignored duties to see some attention between routine – and boring – post mortems on those weak souls who couldn't cope with the weather. Sherlock had been sulking due to the lack of cases and had trudged from the Yard all the way over to St Bart's on foot to keep himself occupied, and he thought, to prove his superiority over idiots like John who'd been stultified by heat, when he found himself stopped abruptly in the doorway of the lab. His mind went dark and empty, like the evening skyline during the blackout he'd sat stonily through a week before when John declared that over-use of cooling devices in the Greater London area had put too much demand on the power grid and they'd been subjected to a bit of "load shedding" to regulate supply.

In a moment or so, the porch lights on the mind palace flickered back on and he shrugged off the momentary lapse. He'd had to check for a physical barrier, firstly. Seeing and feeling none, he frowned down at his feet and twitched his toes to confirm that he'd sustained no injury. He'd spurred his transport back into motion, still watching his lower extremities for signs of rebellion, and looked up as he went to push open the lab door, only to suffer another abrupt blackout.

Thankfully, he was quick to find the mental fuse box in the dark and he flipped the switch to restore supply. He became aware of several things at once, all overwhelming sensual stimuli. The usual smell of vague decomposition, powerful disinfectants and preservative agents filtered through the partially open door. This was normal. His hands were poised; fingers open and thumbs roughly six inches apart on the two halves of the lab door. This was normal, although he felt a tension seep into his digits and perceived a slight clenching as his fingertips slid imperceptibly across brushed aluminium panels. He heard tinny Top 40 pop rubbish coming from the cheap radio suspended over the sink and a woman humming along. Again, this was normal, though the voice was recognisable as Molly's and he couldn't reconcile the sudden involuntarily tightening of his abdominal muscles with previous anecdotal interactions with her that his mind supplied and that in itself was unusual. He also couldn't see her.

What he could see, though, was a triangular expanse of flawless alabaster skin. The plain was divided into perfect hemispheres by the ridges of spine and disappeared into the waistband of a long, diaphanous skirt – cheesecloth? No, fine like lawn or muslin – of cobalt and ruby paisley. The woman shrugged one shoulder and a cascade of long hair tumbled over the curve of delicate clavicle and scapula suddenly.

Sherlock felt a foreign surge of electricity, of fire, of something like the two combined that made him go rigid. He swallowed the sound that was threatening to emerge audibly from his throat but allowed himself to exhale. His mid-section was still locked tight and the breath made him aware of how much his muscles strained at that moment.

The colour of that hair and the humming were eventually introduced to logic, but his pulse hammering loudly in his ears made it hard to focus his attention. His eyes fixed on curls at the end of those silken lengths, took in the slight muscular twitch indicating sensitivity (ticklish back?) and stopped on twin brackets resting above the encroaching cotton; dimples. An errant thought swooped through: how delicious, how sublime it would be to tongue those depressions either side of the spine and apply infinitesimal pressure with only thumbs to stroke the fine hairs undoubtedly dusting that tiny plateau.

A sudden realisation:

"Molly…"

She turned suddenly, almost guiltily, and then tensed at his tone with a question visible in her eyes.

He had to admit he sounded drugged to his own ears.

"Hello, Sherlock," Molly managed. She flushed and the rich, dark blue of the lawn enhanced her heightened colour to a shade he found unbearably arresting. The dress was perfectly modest from the front: a prim, high neckline lay flat to her collarbone and ended in slightly ruffled cap sleeves. The skirt was full and hung to mid-calf. No sane person would wear open shoes in a lab, and Molly's feet were encased in flat-heeled, soft tan leather shoes that had long straps criss-crossed around her ankles Even if he hadn't seen her back, he'd have known she wasn't wearing a bra from the two pert points slightly protruding from the bodice.

The heaviness in his body made sense then. Arousal. He didn't allow it to happen often and as such, the knowledge filled him with dismay. He could feel himself embarrassingly erect, growing more so considering learning the texture of a certain set of areolas against his cheeks, his lips and- NO! Molly was one the few unfortunate recipients of his attempts at friendship and as such, she was accorded respect and his protective energies and apologies when he could muster them. The divergence down this path of – lust? What else could he call it? It was wrong and seemed perverted in light of the hereto platonic esteem he'd held her in. She counted. She also had him rock hard and as mortified as an adolescent over it. Luckily, she appeared not to have noticed and was seemingly engrossed in scuffing her toes against the speckled lino floor.

Aware that he was awkwardly silent even more than usual, he cast about for a rejoinder.

"Molly," he said again, at something of a loss.

She seemed as uncomfortable as he. "Sherlock," she replied slowly after a moment.

He heard her tongue linger over the ultimate syllable of his name and he suppressed a shudder at the sound.

"Are you, by chance, wearing your dress backwards?" he asked before he could stop himself.

Molly reddened to a lurid shade and leaped for the lab coat bunched on the benchtop nearby, shrugging it on quickly. Evidently relieved to have her shroud back in place, she muttered an apology.

For the life of him, he couldn't remember why he'd made the trip there and allowed his mortification to carry him away in a strategic retreat. Molly would be well used to his antics and wouldn't expect a farewell.

He wasn't sure he was capable of giving one.

He made it back to the flat, mind awhirl, and clambered into the shower, disrobing once he was under the frigid spray and casting his sodden clothes onto the bathroom floor absently. His mental palace, a normally impregnable bastion of sense and unblemished reason, was being overwhelmed by Molly. He replayed the scene in the lab endlessly, remembering against his will all of the…urges…he'd had, that her back had forced him to have. He envisioned all wings of the mind palace overrun with marauding forces tearing through the orderly stacks to access memories of Molly, looking for other times he'd suffered this painful awareness. He somehow also retained some capacity to imagine more…satisfying… potential outcomes for the debacle. Pin points of cold were prickling his back, his neck, his shoulders and yet the heat persisted. Grew. He noted in passing that he was touching himself without thought, that his hardness continued unabated by the icy water.

"What have you done to me, Molly?" he muttered, approaching the peak.

He very rarely indulged himself in this way – only when necessary, only when his body required the release that he never allowed it through other means – and despite being mechanical, it usually took a good half hour. He'd never been consumed with thoughts of anyone while he did it, in fact, he took pride in controlling his body to the extent of being able to attend to the distasteful task while thinking of more productive things. But he was consumed with Molly, of his friend, he was shamefully going to allow himself to finish this way; using his excellent memory to replay stimulus for his shower masturbation.

He was never fully able to evict the marauders from his mind palace after he allowed them to overrun it. There were too many priest holes and secret rooms for them to hide in and he grudgingly came to accept that the labyrinthine nature of his mind palace was not ideal in situations of less than complete discipline.

The Summer progressed, swelteringly slow and increasingly awkward. Fewer cases meant less time at St Bart's and Molly was always wearing her lab coat when he saw her from then on. He never brought up that night, and she had the good grace to pretend it never happened.

Gradually, he told himself he was regaining control, but he worried over what the repercussions of his lapse might be. His thought processes were generally as swift, vital and effective as always, though Molly and Molly-related things crowded into the empty spaces and the pauses at the end of sentences as he drafted them internally. He'd permitted himself only one other…occasion… and told himself the several wet dreams didn't count because they were involuntary and he'd gotten over punishing himself for basic human bodily functions as a child.

The weather began to cool enough for John to start wearing trousers again like an adult and there began to be frequent light showers to break the heat down to almost a bad memory.

In one such shower, during the late afternoon when it was still light out but growing greyer, he walked to St Bart's with his Belstaff open to dissipate the heat from exercise and the collar tugged up over his neck to try and stop moisture trickling down his hair and seeping into the back of his shirt. Few people were out for once; everyone seemed exhausted after the intensity of the Summer heat and he'd noticed en route that the restaurants and bars were comparatively quiet.

One of the members of his homeless network was established on a bench on the path to the hospital and he killed a few minutes casually asking after leads or tip-offs, only a smidge surprised there were none. He bid Marcel farewell and resumed his trek. As he crossed the street to passel of Mrs Hudson's wizened cronies bearing down on him, there was a crack of thunder overhead and the rain started to beat down in a comfortingly familiar heavy tattoo. 2 minutes away from St Barts, he stopped under the striped awning of a dress shop specializing, apparently, in "Mother of the Bride Ensembles" to steel himself.

"I might see her," he told himself, as he had on each excursion since That Night. "I might not see her. I can trust myself because I have greater internal fortitude than most men and I refuse to allow myself to become enfeebled by pheromones."

With that, he swept out from under the awning and down the street to St Barts. As he crossed the virtually deserted plaza, he spotted a figure kneeling, gathering a miscellany of dropped possessions.

Molly.

His heart stuttered to an immediate standstill, but then surged back into action double time.

"Get it together, man!" he growled to himself, stopping before Molly.

She looked up, surprised. "Oh, Sherlock!" she gasped. "Did you say something?"

Childhood training in manners dictated that he also kneel to help Molly accumulate what he expected was the contents of her handbag. He scooped a small mirror and packet of safety pins up from where they'd landed near an abandoned focaccia on the pigeon-speckled concrete and when he turned back, he was startled by her scrutiny and helpless to prevent himself from meeting her eyes.

"Get it together, man" he repeated automatically in a slow, chagrined monotone.

Molly flushed. "I am clumsy, I know," she said, taking his words as a chastisement.

He didn't trust himself to answer, or to risk skin contact by handing back the other items he retrieved. He stashed the lipstick, bag of tampons and what he believed might have been a lonely headless Percy Pig absently into his coat pockets.

Molly stood then and he nearly choked on his tongue as he discovered that the rain had rendered her pale pink blouse transparent and cold had caused her nipples to harden, this time against the insubstantial lace of a bra he could see clearly below the wet polyester. She folded her arms over her chest, obviously uncomfortable, and he noticed her lack of jacket, coat or even hideous cardigan.

"I'll- I'll walk you," he said, slowly rising to his feet. He swept the Belstaff off his shoulders and slowly wrapped it around Molly. She shivered – from cold? – and snuggled into its weight and warmth with a grateful smile. Despite the rain now soaking his shirt, he felt a familiar surge of heat and tamped it down as best he could. He maintained eye contact, strangely delighted by seeing Molly in his coat and pleased by her reception of his uncharacteristically chivalrous gesture.

"But I'm going home," she said, disappointment evident in her tone. The rain had plastered errant strands of her hair to her face and she looked up at him solemnly.

"Then so am I," he said, pushing the latest case out of his mind, at least for an hour.