The letter itself is not concerning; far from it, he feels almost lightheaded with relief. His blood results have come back negative; he doesn't have HIV.
What he has is, at this moment, far worse.
He has Mycroft Holmes on his tail.
The note at the bottom of the typewritten letter is short and to the point; his assistant has probably written it.
"Dr Watson.
I would like to speak with you at your earliest possible convenience.
MH"
Well, he thinks, with a rising feeling of hysteria, at least he exhibits a little more tact and courtesy than his younger brother.
Said younger brother is lying in his favourite position on the sofa, fingers steepled underneath his chin, eyes closed. There are no cases; he's been working through anything that Lestrade has thrown his way voraciously, trying to distract himself. The problem is, the criminal classes are doing little of note. It's like they want him to be bored.
The crux of it is, he has decided not to pry into whatever is going on with John, but to do that he needs to be entertained, his mind needs to be occupied. With nothing to do, he physically can't help but to think about his flatmate.
The way he had collapsed the previous evening, as though his body simply refused to carry his weight; and Sherlock knew that feeling, from too many sleepless nights and chases around the city, knew it all too well. The feel of John's bones under his skin as Sherlock had dragged him to the sofa, the loll of his head, exhausted, to one side, the dark shadows under his eyes.
He thinks of what Mycroft said, and wonders whether his brother is right or not.
He wishes that he could understand.
John rings the bell for his next patient, eyes flicking unconsciously down to the letter on the desk. He can't avoid Mycroft, he knows; but he doesn't have a contact number for the man. Every time he has seen him has been on Mycroft's terms.
There is a tap at the door and a creak as it opens, and John looks up with a smile that fades to a frown, although his lips twitch in an ironic laugh.
"Mycroft" he says, torn between giggling and sobbing.
"I took the liberty of arranging an appointment at a mutually convenient time" he says, arranging himself disdainfully into the chair in front of John's desk.
"Yes, I see. Well, good."
Mycroft pins him with an uncomfortable look.
"I do hate to get involved in my brothers affairs, Dr Watson, but I'm sure you understand the delicacy of the situation."
"I'm afraid I don't understand how my confidential medical records are any of your business, no."
He can feel his temper building, much as he tries to cool it with slow, deep breaths, and wonders what the repercussions of taking a swing at his flatmate's powerful, genius brother would be.
"Doctor Watson, please do not take me for an idiot. You and I both know otherwise."
"Well, frankly you're acting like a lunatic" exclaims John, his voice going up a pitch that he wishes it hadn't.
"Must I spell this out for you?"
"Please do!"
Mycroft sits back, looking faintly perturbed, as though John's ignorance has somehow surprised and disappointed him.
Actually, he usually looks like that. John's starting to become accustomed to it.
"You are pursuing a relationship with my brother, which will eventually become sexual in nature. You have concerns about your HIV status; recent concerns, which implies you have been engaging in unsafe sex. You have done everything within your limited power to prevent my brother finding out about this. Exactly what part of that would I not be irate about? He may be annoying, but I am duty bound to protect him."
John freezes, unable to blink or breathe for a moment. The words jumbled together in his head; he couldn't have heard Mycroft, that was the only explanation. It must have been one of those ridiculous examples of completely mishearing a very normal phrase to mean something else.
"I…um…did you just say 'pursue a relationship?"
Mycroft frowns at him.
"A romantic relationship, you mean?"
Mycroft was beginning to wear the look of a man who feels he may have bitten off more than he can chew, but still says nothing.
"Mycroft, have you met your brother?"
Laughter is bubbling up inside of him, despite the gravity of the situation, despite the fact that if Mycroft really believes this then he has probably told Sherlock, and god only knows how he would react.
"I was under the impression…"
"Clearly. You were wrong."
Mycroft at least has the grace to appear abashed for a moment before his brow furrows and John knows that he is ticking through the facts, evaluating and contemplating, re-working his hypothesis. It is unnerving not only to see that expression on another face, but to know so intimately what it means, and the laughters stills and dies in his throat.
"Please believe me when I say I would never do anything to harm Sherlock" he says softly, "And please respect that fact that he is doing his best to give me as much privacy as he is capable of."
Mycroft genuinely does look surprised at that, his eyebrows raising into his hairline.
"How interesting" he says, which doesn't fill John with a great deal of confidence, but he does seem less irate and more contemplative which is a definite improvement.
Mycroft leans back this time, regarding John through a veiled gaze.
"You should have more faith in my brother, Doctor. You will find that he is not as untouched by human emotions as he would have everyone believe. You will probably find that he can actually help you, if you give him the chance."
He takes his leave while John sits, stunned into silence, and wonders what on earth has just happened.
Sherlock gets up to use the bathroom, and when he comes back Mycroft is sat opposite his chair.
He wishes his older brother wouldn't do that. It's annoying.
"What do you want?"
Mycroft doesn't speak for a moment, gazing contemplatively at Sherlock's feet.
"You need new socks. Those ones look awfully threadbare."
"Please tell me you did not come here to talk to me about socks."
Mycroft looks fleetingly uncomfortably and shifts in his chair, ostensibly to cross his legs, although the underlying unease is not missed by either of them.
"I went to see John today."
"Ah."
Mycroft sits back in surprise again, having expected Sherlock to react a little more…well, violently.
"Did you upset him?"
The question is phrased simply and calmly, but only a fool would fail to notice the undercurrent. Mycroft may be many things, but a fool is not one of them.
"I startled him, I think."
"Did. You. Upset. Him?"
The danger is overt now; it has been a long time since Mycroft and Sherlock have come to physical blows and they both remember how the last one ended (Mycroft's nose has never been the same), and the older man holds out his hands placatingly.
"No. I-"
"What on earth is going on here?"
Neither of them had noticed the sound of uneven footsteps coming up the stairs in the tension, and now John is stood between them, wide eyed and confused. Sherlock is on his feet, aggression radiating off him, and Mycroft is leaning back in his chair, his hands still outstretched in an attempt at a peaceful gesture.
They probably look ridiculous.
John clears his throat, still looking between the two of them, and obviously decides that this has the potential to be far more trouble than it's worth.
"I'll just…um…leave you to it then" he mumbles, and hobbles up the stairs.
Sherlock glowers at Mycroft.
"This isn't over" he promises.
The sad thing is, Mycroft thinks, Sherlock is right.