"I think Sherlock's cheating on me."
Lestrade looks up from the folder on his desk, his eyes wide at John's announcement.
"Impossible," Lestrade replies after a long moment and motions John into the seat at the other side of the desk. John drops into it, lowers his head to his upturned palms and groans loudly. "What makes you say that?"
John shrugs, keeps his head down and sighs. He doesn't answer because he's not sure; there's just this feeling that there's something he is missing – something that he should know. It's like an itch, burning hot and hungry under his skin and every time Sherlock swans out of 221b in his finest suit, hair tidied and the curls suppressed John has to fight the urge to follow him down the street, to wherever it is he goes.
It hurts.
"I don't know," he mumbles into his palms.
"There must be something," Lestrade says quietly and John nods slightly, breaks it off then shrugs again. "John..." Lestrade sighs and John looks up, looks over to him and he knows what a sight he must be (or he can guess, because Lestrade looks shocked for a moment or two before he composes himself). "Is this about Victor Trevor?"
"Who?"
Lestrade freezes momentarily, his brows flicker together and nineteen months ago John wouldn't have noticed but he's learned some of Sherlock's ways and he notices, even though it only lasts for a fraction of a section before Lestrade flattens his features and shakes his head.
"No one."
"Lestrade-"
"Look." But he pauses, doesn't say anything and John feels his chest tighten, feels a coil wind around his guts and when he looks down to his hands, they are shaking. He clenches his fist. "Look, the only person to talk to about this is Sherlock. I shouldn't have said anything."
"Lestrade," John grits out passed the rising lump of dread in the back of his throat. "Who is Victor Trevor?"
Lestrade looks pitying, for an instant. John flees.
–
In 221b, when John gets back, Sherlock is sitting in the armchair reading a book (Chomsky, On Language) and it takes all of John's effort not to reach out and whip the book from his hands. Takes all his effort not to take Sherlock by the shoulder and shake him.
Instead, he moves closer, dips his head down to press a kiss to Sherlock's temple and pauses on an in-breath because-
"That's not your aftershave."
Sherlock freezes, then the hand holding the book up lowers and Sherlock turns to look at John. They're very close and John dips his eyes down, down the pale column of Sherlock's neck, his throat, his chest – all of which, usually, remain unmottled but there, not quite hidden by the edge of his indigo shirt is a purple blemish, a tiny sliver. John reaches up, Sherlock tenses.
"John-"
"Don't. Just..." He takes a breath, doesn't really feel anything. Steps back. "Victor Trevor, I presume?"
Sherlock looks startled and John hates that.
"How did you-" John laughs and shakes his head. "No, I mean – it's not what you think."
"It never is, Sherlock." He pulls his lips between his teeth and shakes his head.
He steps back, once. Twice. There's a pause, during which he waits but Sherlock doesn't fill the silence.
John leaves.