Sherlock regrets his decision to have John go undercover at the university. It's nothing John's done to turn him off; quite the opposite, in fact. John is a hit with the students of introductory Anatomy & Physiology. He knows his subject backwards and forward, both due to his experience in Afghanistan and the crash course Sherlock sat him through the night before. He is soft-spoken and personable, just the right side of self-conscious of the auditorium of young students listening to him speak. He could be louder, Sherlock expects, but it isn't as though anyone in back is there to learn or anything so productive. No, they've come to scope out the instructor who reminds them of the father who never loved them enough and the sort of man they'd like to take home to meet him.

Sherlock thinks it's repulsive. He doesn't think of the fact that he's seated in back, too. He's learned all this before; John's ineffective though well-meaning repetition need not be retained. (He gets along fine with this father: their mutual agreement never to speak suits them. John would hate him on sight.)

At centre stage below, John is uniformed in pressed trousers and a smart shirt with a solid sweater vest to round it out. His sleeves are rolled to just under his elbows, as they tend to be by the final session of his lengthy days. He looks worn out but not beaten, something of a reassuring smile remains on his face belying his scuppered yawn. John turns momentarily from his class to reach into the podium.

Ah, the moment has arrived.

His careworn blogger sets a pair of rectangular frames on his snub nose. "Sorry, bit of a long day," he excuses and carries on, blessedly unaware of the wave of seduced sighs that pummel Sherlock's sensitive ears where he sits. Sherlock presses his palms more tightly together, trying and partially failing to observe past the stench of pheromones surrounding him. There's a fledgling serial killer in their midst whom they may be in position to apprehend, if only Sherlock can concentrate.

Young enough to pass for a traditional student. Perhaps in fact an enrolled student. May have already completed the course but sits in on lectures to brush up. Their perpetrator has an appreciation for formal learning Sherlock respects though he doesn't share it. He remains a course or so away from his degree in Chemistry. Given that it's yet to impact his work, he doesn't see a reason to pursue it. Mycroft and Mummy pester on the matter at least once annually to no avail.

Sherlock makes a note to review the headshots of the students enrolled in each section of the course. John says something and the class laughs. Half of them don't even understand it. A joke about valence electrons? Sherlock is pleased, reluctantly. It appears John's been reading Sherlock's website, after all. The only one, John is likely to tease. Sherlock minds much less than he could. He doesn't think there's a worthier readership to be found.

The class ends on a high note and the hall empties at a glacial pace, a line of students queuing up for words with John. Sherlock catalogues each one and checks them off against the vital statistics they've provided to the university. Enrolled, visiting, disenrolled but unaware, skiving off another class to be here (wrong textbook), enrolled, graduated, back for another degree (not in this subject), early placement. 'Boring' is too generous a description. The quantity of mobile phone numbers indiscreetly crowding John's podium reads as equally mind-numbing. He'll want to call them, men and women both, but he won't.

When the crowd has been reduced to a singleton, Sherlock descends from his place at the top of the auditorium to where John is speaking to an overeager straggler. Average height for a woman, light eyes, olive skin, and dyed hair: Besotted. John's perched on the corner of his desk, peering up at the young woman attentively. The glasses persist, naturally. Sherlock notes the breathiness of her voice immediately, surmises that her eyes are more dilated than required by the fairly lit room, and pinpoints the moment she has summoned up her courage by the rush of blood to her cheeks. He quickens to slip into the space between student and acting teacher, gleefully.

"John, we have reservations."

The look John confers upon him is the least impressed he's appeared to date. "Do we?"

"Mmm, yes. The Savoy at seven with my mother, don't you remember? You've been promising to meet her for months now and she's in town. You aren't backing out, are you," he continues as though the girl isn't there. "I'm beginning to think you aren't serious about our future at all."

John sucks his teeth and grits them before planting an unconvincing smile on his mouth. "Right. Your mother, Mummy dearest. Can't wait. I hope you invited your brother, because I'll need to give him a call if you forgot." He firmly shoves Sherlock aside to speak to the girl, who, Sherlock muses, appears precisely as engrossed as she was to begin with. Odd, the implication of a present relationship is usually enough to repel most interested parties. Suppose she's another sort of woman. "Savannah, I'm afraid, we're going to have to cut this short, but you can contact me via email and I'll get back to you as soon as I can."

She clasps her hands in front of her and smiles, teeth blinding. Bleached, store brand. Lovely, he almost rolls his eyes. "Thanks, Doctor. Have a great evening. Both of you." She takes her leave with a gallant wave. Sherlock replies with a mocking facsimile. John smacks his arm with an A3 notebook soon as the door swings shut behind her.

"Be nice! Or there'll be more than one person in my classroom looking to kill."

"You'd be driven to remorse in minutes. If you're lucky the guilt would kill you before boredom set in." John, staring after his departed student, hasn't a word of reply to that. He wets his lips. Really, John, a student? Sherlock is unclear as to whether his mortification is at John's poor taste in general or relative to the obvious.

"Sherlock, I've just had a thought."

He doesn't suppress his snort this time. "Shall we take out an advertisement in the Times? This shining occasion is one of such rarity that it must be shared. Please, do. Your thoughts are always so entertaining to me."

Another whack. "Wanker!" John glares up at him, eyes made more striking for being magnified. His eyes aren't only blue. "Anyway, that girl, the one who we've just been talking to?"

"What about her?" Sherlock would rather delete her out of hand, plans to do it when he can.

"Sherlock, there isn't anybody named Savannah in this class." Narrowing his eyes, Sherlock reviews the names on his mental roster. The only matches he can find are quickly discarded for unsuitability.

"Nickname," he hazards, knowing that to be wrong.

"I don't think so." John's hunches, though scientifically unsound, have a worrying tendency of being correct. She wasn't exhibiting arousal. Or not only arousal. Excitement, adrenal response. She recognized both of us.

Sherlock's next thought is, That's our killer. Bugger me. He is on her trail in seconds, John sprinting at his heels full-tilt, no questions asked. They get their killer, but those damnable glasses are lost in the subsequent pursuit. They rather suited John, Sherlock thinks, as the student body would likely attest. Sherlock isn't sure he doesn't feel a moment or two of loss, himself.