A/N + Disclaimer: I do not own Sherlock, nor Mycroft, nor anyone you may recognise at any point.

So, you should know this actually started as a Molly/Mycroft one-shot, then I very soon realized that Molly was getting out of character (and she deserves better, Ms. Hooper, she does, and I will be working on it). So, yeah, I guess here goes yet another attempt at a Mycroft/OC pairing, sorry. If you choose to picture the OC being Molly, I won't hold it against you :D Also, not sure where or how far this will be going, depending on my time and encouragement. The plan is to switch between Mycroft and OC's point of view and very, very slowly let it develop (not sure what "It" is going to be yet).

Some "technical" notes: English isn't my native language, so bear with me, I'm still learning. Also, I really have no idea of the British educations system or the state of its schools, or lots of other things you may find weird :) I do research, but I also make up stuff as I go.

The chapter titles will, surprise-surprise, follow some well-known Tango-songs.

Tipy, constructive critisicm, are very welcome, please, do review either way.

Chapter 1: Leyenda Gaucha

Mycroft was sitting on a wooden bench, lacing up his shiny new tango shoes (Anthea had picked a pair of black and white flats, which she correctly assumed he would like best. Or rather – dislike the least. They were very suggestive of the 1920ies, for some reason he approved of that).

An ominous frown had settled on his face. A stranger could suppose that he was mildly disgusted by something, as his expression showed a mixture of sulking, a complete averseness to all this and just a faint trace of disbelief, that was more like some residual incredulity over something from a while ago, but recent enough to still make him shrug and shake his head ever so slightly. When he thought about it, that went two ways really: first, he couldn't quite grasp how he had lost the blasted wager (and to his brother of all people… he wouldn't lie – it did hurt). And second, why the hell didn't he just get out of this anyway? Why did he agree to do this? But no, he wasn't going to give his brother the satisfaction of being a bad loser, no, he was going to be the bigger man and show Sherlock that one could lose a bet without having a fit and accept the loss with dignity (well, that was pushing it a bit too far, but… let's just say he was going to bear it and suffer in silence. After all, there was always going to be a next time).

The two young Argentinian tango teachers clapped their hands and everyone moved into the middle of the large dancing room. It had a high ceiling, a parquet floor and two of its walls were panelled with mirrors. Hmm, it could be worse, I suppose….

Yet, his good will was exhausted within few minutes during which the participants in order to warm up had to do a few individual exercises, practice the stance and some of the steps and decorative elements, and yes, there were… yoga moves... Mycroft took a deep breath, and seriously considered if throwing a tantrum wouldn't have been a better, more dignified way out than this.

He simply couldn't believe he had lost. It annoyed him on so many levels. In order to distract himself from this humiliating ordeal, and to get through this abasement faster, he thought he would indulge in a mental exercise... In less than four seconds he determined that his current dancing partner was a teacher (there was chalk on several spots on the skirt of her dark dress, and her hand had that specific touch to it of someone who had to use a sponge soaked with chalk water to clean a blackboard. In fact, to be exact the grey dusty spots on her dress matched the area where one would wipe one's hands clean, which indicated to him that she didn't always bother to wash her hands. Either she didn't have the time or at some point she didn't really care. Now, he knew there weren't any primary or secondary schools in London that would still use an old fashioned blackboard. But, the innovation of the smartboard hadn't yet reached entirely into every hidden corner of some universities and colleges. He also knew, that it were the liberal arts that were more resilient to go with change and progress, but they also were the ones, or at least some of them, that would have been the last to get the financial means to upgrade their equipment. Considering all this, Mycroft concluded that she was very likely teaching some marginalised humanities, and most assuredly not theoretical physics. It took him another six seconds (was he really slipping?) to establish that her area of teaching was music. Her not long, but sleek fingers indicated she played an instrument, most likely the guitar or the piano. No, correct: As their first tango ended and she let go of his arm, he spotted the tiny, barely noticeable bulge of calloused skin on the bottom side of her left index finger. That and the fact that her fingertips lacked the calluses usually associated with guitar or any other string instruments were all really pointing towards… the flute. Yes, her bottom lip looked like it would accommodate its mouthpiece very well. It wasn't too big, but full enough, while her upper lip distantly reminded him of the side shape of a cello…

He frowned as he noticed her cheeks turn slightly red. Ah yes, the blush of the embarrassed… he had stared at her lips a tad longer than what people who adhered to social conventions would consider casually appropriate. He raised his eyes to look into hers, she was now clearly abashed, and managed to contort his lips into something of a coerced smile before returning and fixing his eyes back on her suprasternal notch – a golden rule of every dance class.

Three tangoes later, he confirmed his observations: she clearly had a flawless sense of the rhythm, even though she occasionally seemed to have trouble keeping her balance or discern her limbs to move according to the rhythm - a seemingly paradox trait, yet, Mycroft knew, not uncommon among musicians. He also noticed with amusement she had a slightly impaired left-right-differentiation.

He smirked bitterly: Or maybe she is a nuclear physicist. After all, I did bet that Molly Hooper had taken on violin lessons… And there was the self-pity again.

Ever since Eurus he had doubts about his judgment and his capabilities, and this lost bet was only a confirmation that they were well placed.

"You dance very well," the music teacher said casually at the end of the class as he sat down on the bench to change his shoes. The expression of suffering, of torment back on his face (has it ever left?). He merely gave her a short look and the same forced grimace that one may confuse with a smile, but she somehow sensed it was not, before he looked back at his shoes and neatly, carefully put them away in the box they had come in.

She raised her brows, then said jokingly, imitating a deep voice of a gentleman: "Why thank you, ma'am, you're not so bad yourself." She grinned, but the moment his cold blue eyes met hers she regretted it. She cleared her throat and before she could decide whether to say something else to him or not, an elderly woman saved her by addressing her from the opposite corner of the dressing room, when she asked loudly: "Louise? You in tonight?"

Clearly there were some post-class rituals these people practiced, them being a long cemented group of regular tango class attendees, some of which probably spent their last 20 years going to the same dance class every. single. Friday. night. The horror…

Louise picked her scarf from the bench and while wrapping it around her neck walked a few steps in the direction of the other woman. "Eh-yes, yess, I guess... sure," she said in a low, non-committal tone. She hesitated briefly, then turned around and appeared to be pondering something.

Mycroft got up to his feet, at last wearing his trusted, snug Oxford shoes again, he picked his coat, then his umbrella and the silk bag, in which he had put his tango shoe box, and was about to leave, when the music teacher named Louise reluctantly moved towards him. "Do-do you perhaps…," she started, but his stern look made her nervous and she subconsciously crossed her hands together in front of her, "… w-we are going to a milonga nearby, at the Tango Garden….," she saw him raise his brows questioningly, no, daringly is what it was… like he was daring her to continue…

Dear Lord, was there no end to his torment? Mycroft thought.

"… would you perhaps… like to come?" So there wasn't. He paused for a brief moment, composing himself in order to not sound too morose. There was only so much touching and gripping to a stranger's waist he could stomach on an evening.

"Why thank you, that sounds... delightful, but I'm afraid I'm otherwise engaged. Some other time perhaps," again the forced smile that really was just a faint twitch of the left corner of his mouth, then he gave a small bow but his eyes were already fixed on the exit, "good night."