Inside the college gatehouse. The morning of the following Thursday. In the distance, Great St. Mary's can be heard striking three quarters of an hour. Straight ahead, we can see a part of the sunlit lane outside the outer archway, a group of schoolchildren walking past, all with identical backpacks with a language school logo on it, chattering merrily. To the left, a broad flight of stone stairs descends directly into the gatehouse from the upper floors of the building, marked with a polished wooden sign with gilded letters as "Staircase A". To the right, directly opposite the staircase, is the porter's lodge, with a counter in front and a desk and several cupboards and filing cabinets and technical implements filling the space behind it. A porter is seated behind the counter, a rather overweight, elderly man with huge glasses, busy entering data from a spreadsheet into a computer, typing laboriously with only his index fingers. A pair of girls come walking down the staircase, one exceptionally tall and athletic, with long curly blonde hair, wearing a t-shirt in the colours of the college's rowing team, the other exceptionally short, with a shock of messy dark hair and round glasses that make her look rather owlish. They both have their arms full of folders and books. They nod to the porter - who nods back with a smile - and turn aside towards the open inner archway leading into the college court, probably on their way to a tutorial. A moment later, Sherlock enters from the street, in his pea jacket and tartan scarf again, a laptop bag over his shoulder. He walks with his usual long, energetic strides, his footsteps echoing on the flagstones of the gatehouse passage. The porter looks up.

PORTER: Oh, you were an early bird today.

SHERLOCK (sweeping straight past the porter without so much as looking at him): Miracles do happen, Mr Thompson.

The porter grins after him almost fondly, not put out in the least. As Sherlock passes through the inner archway into the court, we can see that he is smiling, too.

In the court, there is a hum of activity. Students, Fellows and other college officials walk across the scene or stand together in little groups. The eastern half of the buildings - with the entrance to the Hall - is still in shadow, while the western half is already bathed in brilliant sunshine. On this side of the court, on a long wooden bench against the wall, next to an arched open doorway marked "Staircase B", So-Yun is sitting with a musical score in her hands and a pencil between her fingers, sometimes humming a snatch of music, sometimes putting a note into the score. She, too, is in a t-shirt and wears sunglasses. Her bag and a cardigan that she must have been wearing earlier in the day are next to her on the bench. As Sherlock approaches her, she raises her head and pushes her sunglasses up into her hair.

SO-YUN: Good morning. (Looking him up and down) Are you sure you're warm enough?

Sherlock meaningfully raises his eyes towards the perpetually open window of Professor Bergmann's room on the second floor, directly above them.

SO-YUN: Oh. Of course. (Her eyes return to her score.)

Sherlock gestures towards the empty half of the bench.

SHERLOCK: D'you mind?

She shakes her head and moves aside a little to make room. Sherlock sits down next to her and nods towards the score in her hands.

SHERLOCK: What've you got there?

SO-YUN: Chopin. Just passing the time. Violet's still in there. (She pencils a couple of notes in the margin, shaking her head in grudging admiration.) Devious. Clever but oh so devious.

SHERLOCK: Who, McAllister?

SO-YUN (looking up): No, Chopin. But you have a point, too. (She closes the score and smiles.) Although that's probably a case of a black kettle – I mean pot. Whatever.

SHERLOCK: Thank you.

SO-YUN: Don't you wonder why he lets you get away with it all? Sometimes I think he secretly fancies you, or something.

SHERLOCK (in a bored voice): No, he fancies pretty girls.

SO-YUN (with a mischievous grin): But you are a pretty girl. In your own way.

Sherlock's eyebrows fly up into his hair.

SO-YUN: Alright. Only from behind. If I squint.

Sherlock gives her a mock-disapproving look. At that moment, there is a sound of a door slamming shut from the direction of the entrance to Staircase B. Sherlock and So-Yun turn to see what's going on. Violet comes storming out of the open doorway. She looks hurt and confused, close to tears. Looking neither left nor right, she starts marching down the court towards the gatehouse, walking with one of her fists clenched tightly at her side, running her other hand over her face in distress.

SO-YUN: Uh-oh.

She jumps up from her seat and hurries after Violet. Sherlock watches her as she reaches her friend and tries to take her by the arm, but Violet shakes her off, walking on determinedly. So-Yun follows her, and they disappear together under the archway into the gatehouse, turning left to ascend Staircase A to their rooms.

The rehearsal room, some days later. The student orchestra is in the middle of the first movement of Mozart's Flute Concerto No. 2 in D major, Professor McAllister conducting, Violet Westbury in the soloist's place next to him. They're playing beautifully, the cheerful music lighting up the whole room, Violet with her flute putting the birds in the trees outside to shame. It is obvious that she is in fact a very good musician. Even McAllister looks grudgingly pleased. Sherlock and Victor are side by side in their usual places, Sherlock playing with his eyes fast closed, frowning very slightly on occasion. Then suddenly, on a particularly virtuoso part, the flute stumbles, Violet's fingers fumbling slightly on the keys. She cringes and screws up her face in an effort to remain on track, then derails completely, going out of sync with the rest of the orchestra in jarring discord. McAllister lowers his arms. The music breaks off. Sherlock opens his eyes.

VIOLET (blushing crimson): Sorry. I'm so sorry.

McAllister smiles sourly, but doesn't comment. He simply waits for her to regain her composure. She wipes her eyes and takes a few deep breaths.

VICTOR (to Sherlock, under his breath): You really got it all by heart?

SHERLOCK: No. I'm predicting it. (He points his bow at the sheet on their stand.) Works beautifully with something as trivial as this.

Victor inhales sharply and gives Sherlock a look as if to suggest that the latter has taken leave of his senses.

McALLISTER (loudly): Alright, everyone. Back to letter B, please.

Sherlock and Victor return their attention to their conductor. They play.

Some time later, the rehearsal has ended. The members of the orchestra are leaving, Professor McAllister is already gone, and Violet is just clacking her way out of the door on her high heels. Sherlock and Victor are at one of the tables along the back wall of the room where the players store their instrument cases and bags during rehearsals, packing up their violins.

VICTOR: You know, about what you said the other day.

SHERLOCK: Mmh?

VICTOR (quietly): About her, I mean. (He jerks his head towards the door.) And him.

SHERLOCK (indifferently): What about them?

VICTOR: Well, you know – she's in Performance, she wouldn't need to – you know. She'd get the solo parts anyway, for practice. And I don't think she's the type to -

SHERLOCK: I said she thinks that hooking up with him would help her through exams. I never said she'd done it. Though it's probably not going to be long now, with only two weeks to go and her skirts getting shorter by the day.

VICTOR: What? She's been wearing that black one all term.

SHERLOCK (sarcastically): Oh, listen to the expert.

VICTOR (annoyed): I don't care what you think, but she isn't stupid. She's making a real effort. Spends hours in the library with So-Yun. I think she's just really worried about exams. Very, very nervous, you know. People are, sometimes.

SHERLOCK: Nervous enough to throw us out of the same piece three times in a row?

VICTOR: Yes! Isn't it obvious? There's nothing wrong with her playing, normally. But right now, she's just getting worse and worse. She's desperate. She's panicking. And I think McAllister knows it as well, or why else would he be so patient with her?

SHERLOCK (disdainfully): He's patient with her because he certainly wants to shag her, and if she has any self-respect left she isn't going to let him if he tears her to pieces like he would everyone else. (Victor looks unhappy, but doesn't reply.) And what about keeping us all waiting for close on fifteen minutes in the first place, and then rushing in all flustered and out of breath and oh-so-busy and sorry sorry sorry but I'm a diva so I'll keep you waiting all I want? What kind of exam nerves make you behave like that?

His voice has got louder and louder, and Victor looks round in embarrassment to check whether anyone has heard, but the room is now empty except for the two of them.

VICTOR (hotly): Well, anyone can be late some time, can't they? She's never kept us waiting before, I'm sure there was a reason, so don't go on about it, will you?

SHERLOCK: Oh, and you never complain about people stealing your time, do you? How come she's allowed to do that when nobody else is?

VICTOR (not rising to the bait): Well, all I can say is, you've got it wrong, all wrong.

SHERLOCK (after a moment's pause, coolly): I wonder why you care.

VICTOR: About her? (Scathingly) Because she's a fellow human being? Why don't you?

He closes the lid of his violin case with a snap, picks it up, turns on his heel and walks out of the room without another word, leaving Sherlock behind, looking pensive.

The college library, a couple of days later. A large room filled with rows upon rows of bookshelves, and on the window side, a long table with desk lamps on it. Muted light, and muted conversation from two or three students sitting at one end of the long table with their coursework spread out before them. On one wall, well hidden behind the last row of shelves on that side of the room, there is a rack on which scientific journals and periodicals are displayed. Sherlock is sitting cross-legged on the floor in the narrow passage in front of it, a dog-eared issue of "Nature" open on his lap, absorbed in one of the papers, his chin resting on his folded hands. There is the sound of a door opening and closing, and of footsteps – muted by the thick carpet - coming down one of the aisles between the shelves to the long table. Sherlock doesn't react. A moment later, familiar voices come floating towards him from the direction of the table, and we can see him perk up his ears, though outwardly motionless.

SO-YUN (off-screen): So, shall we go through this one again?

VIOLET (off-screen, rather unenthusiastically): Alright.

Silence. Sherlock turns a page of his journal.

SO-YUN (after a while, still off-screen): Now, look. Figured bass really isn't rocket science. All you have to do is learn the most usual combinations by heart. And then remember a set of rules. Like here - when you have an accidental without a number, it always refers to the note a third above the lowest note.

VIOLET (off-screen, with a sigh): Right. So here's the first inversion – I mean the second…

Silence, except for the scratching of pencils on paper.

SO-YUN (off-screen): Sorry, no. That one is with a number, so it refers not to the third but to the interval the number indicates. The fourth, in this case. (A short pause. In a different tone, very sympathetically) Oh, don't. Don't, Violet. You'll be alright.

In one smooth and almost inaudible movement, Sherlock is on his feet, the journal still in his hands. He backs away slowly and silently towards the centre of the aisle, where a gap between the books on the shelf at eye level gives him a limited view of the long table. Through a maze of metal boards and racks, he can see Violet sitting with her face buried in her hands, crying quietly. So-Yun, next to her, has her arm around her, patting her gently on the back.

VIOLET (with a sniff): I'm sorry. I'm so sorry. You're so patient and so kind, but you're wasting your time, So-Yun. Really, I can't even think straight any more. I've tried everything, everything. I've gone out of my way to figure out what's expected of me, and I really can't keep relying on other people to help me with that. It's not fair that anyone should get into trouble on my account, just because I can't – I feel so guilty – (She starts crying again.)

SO-YUN (kindly): But you're not getting me into trouble at all, dear. I enjoy explaining stuff, honestly. It helps me understand it better, too.

VIOLET: It's not just you.

SO-YUN (encouragingly): See, so there are lots of people here who haven't given up on you just yet! Isn't that nice to know?

Violet sniffs again and blows her nose.

SO-YUN: Shall we try again?

VIOLET: Alright.

Sherlock edges away again carefully, back towards the periodicals, replaces his journal on the rack where it belongs, then – no longer concerned about secrecy - turns on his heel and walks down the aisle towards the exit. In the door, he almost bumps into Sebastian Wilkes, who was just about to enter, his head down and his eyes on a reading list.

SEBASTIAN (looking up): Whoops. What are you doing here? You know it all anyway.

SHERLOCK: Just verifying a theory. And now excuse me, I need to make a phone call.

He walks away, taking his phone out of his pocket. Sebastian shakes his head after him, and we cut to -

The office of an obviously important person, somewhere within a government institution in London. Wood-panelled walls with portraits of grim-looking besuited men in thick gold frames, heavy leather chairs, and a huge desk with an equally heavy elderly man sitting behind it. He has a file open on his desk and is reading in it. In front of his desk stands the Mycroft Holmes of ten years ago, the hair on his forehead not yet quite as sparse, wearing a well tailored but otherwise completely unremarkable dark grey suit. The important person looks up from the file, closes it and hands it to Mycroft.

IMPORTANT PERSON: Excellent, Mr Holmes, excellent, as usual.

MYCROFT (deferentially): Thank you, sir.

IMPORTANT PERSON: Now do as well again on our position regarding Chechnya, and I'm convinced we may expect truly great things from you in the future.

MYCROFT (smiling proudly): Thank you, sir.

At that moment, the phone in his pocket starts ringing. He claps his hand to it in alarm, deeply embarrassed.

IMPORTANT PERSON (generously): Oh no, take it, please. We were finished, I believe.

Mycroft receives the folder back from his superior, sketches a little bow and backs out of the room, his phone still ringing. We cut to the corridor outside the office. Mycroft closes the door behind him, takes the phone out of the inner pocket of his jacket and glances at the caller ID. His expression changes instantly to one of extreme annoyance.

MYCROFT (taking the call, without preamble): Didn't I tell you not to call me at work unless – (He pauses and listens.) Oh, urgent, is it? Well, out with it. What is it this time, exam nerves, another hopeless crush, or do you want me to do you a favour? (He listens to the reply and frowns.) What do you mean, a combination of all three?