Greg feels well-loved, that evening when he first recognizes that Mycroft has positioned Greg's "I'm just in a damn good mood today" and the "I need a pick-me-up" CDs on the most visible shelf: if Greg were running his eye over his collection, looking for a suggestion, these would most readily come to hand. (That is what Mycroft would suggest, if he were present to suggest it: be happy.) Greg laughs to see that his "I'm feeling sentimental about my boyfriend" CDs are just below. Comfort for when Greg is feeling lonely, or was that a bit of actual self-indulgence on Mycroft's part? Greg hopes for the latter—even now, the man is too good at self-denial—but he would be content with either. He grins and gets up to examine his shelves properly.
It's not until Greg is down on the floor, craning his head to see what Mycroft has chosen to put down here, as far out of the way as he could place them and still pretend that he was just reshelving Greg's CDs, that Greg fully understands. It's mostly thrash metal down in this hard-to-see corner. Greg might attribute that to the prejudices of a posh who founded a club in which no one is allowed to bloody speak for fear of ruining the atmosphere, but Suicidal Tendencies, which Greg plays when he is exhausted of being angry and ready to be done with it, is up there on the third shelf, easy to find. No, it's not musical taste, because in among the thrash metal is Etta James's faultlessly exquisite Mystery Lady. Greg takes a deep breath. Mycroft's eye was unerring: this is the music Greg plays when he is already unhappy, and wants to feel worse.
Greg sits back on the floor, and looks up at the shelves again, taking in the whole of it. It's not merely that Mycroft can distinguish one punk album from another (although for all that Greg knows, Mycroft merely read Greg's emotional states from his thumbprints on the jewel cases, a heady thought in itself), nor even that Mycroft knows that this album of jazz ballads takes Greg differently than that one. No, Mycroft has arranged it so that every time Greg feels the need to give in to his own self-destructive impulses, he must get down on the floor and stretch. And in that moment, Greg might remember why they are so awkwardly placed: someone loves him enough to understand the difference between Sarah Vaughan in HI-FI and Mystery Lady, and cares enough to put one here and the other there.
It is the most brilliant love letter Greg has ever seen.
Greg pulls his hand back, not touching that final knot of CDs. Dust sends only one of the Holmes brothers into rhapsodic joy, but Greg reckons that both can read it well enough. Greg is no Shakespeare, and he may never write a love letter as eloquent as Mycroft's, but he can start so: six months from now, two years from now, however-long-Greg-and-Mycroft-last from now, Mycroft will glance at that last cluster of CDs, and read a love letter of Greg's own. One written daily, little by little, in the sincerity of dust.
And if some evening Mycroft has to endure an extra text or five because Greg is forgoing the terrible beauty of Mystery Lady, well, such things can happen to a man, when he is so transparent about being in love.