It's not just a matter of physical attraction, John thinks, studying the crime scene in front of him. If it were that, he'd lock himself and Sherlock in the flat on Baker Street and shag him silly for three days. But there are two problems with that: first, Sherlock is on a case and it's looking to be a long one; second, alpha or not, Sherlock isn't one to be swept away by his hormones. Which means a long conversation about consent versus disinterest.
John wouldn't necessarily mind having that conversation with Sherlock. Only he has a sneaking suspicion Sherlock would take any such discussion as the preliminary to the whole complicated mess of bonding. He shouldn't -- Sherlock has made his desires (or, more accurately, lack thereof) on the subject very clear. Only John's had to wonder over the last few days, on the evidence of a handful of sidelong, considering glances since his own scent has started to change, if Sherlock's stance on the subject isn't undergoing adjustment.
Since Irene Adler, John hasn't bothered denying the complexity of his attachment to his flatmate. But his heat's in two days, and he's looking for a good shag. Nothing more, nothing less.
Sherlock has just about finished his examination: no corpse this time, but enough blood for two bodies, John estimates. He momentarily lets his attention drift, considering the other people at the scene. Not a lot to choose from, here; in a way managing his heats had been easier before he'd been invalided back to London. A larger pool of candidates: fellow army blokes, a handful of nurses. And they'd mostly been younger, as well, John included.
Here, though -- Sarah and Jeanette and the other beta girls in the middle were all out of the question. John had either burned those bridges himself or Sherlock had burned them for him. Likewise Anderson was out of the question -- married, for one thing, the affair with Donovan, another, Anderson's personality the largest stumbling block of all -- though it has been a while since John's enjoyed the company of an alpha during his heat. Simpler to spend the time with a beta; more chance they'll end up actually pleasing each other rather than just fucking mindlessly. Not that mindless fucking doesn't have its place, and not that he hasn't been with a considerate alpha or two or five.
Lestrade, now. Sherlock has straightened and is practically in the DI's face, though he's merely running through his observations rather than accusing Lestrade of stupidity or short-sightedness. John's always been impressed by the beta's refusal to back down no matter how hard Sherlock pushes; his relative unflappability makes sense given the number of other alphas he has to deal with daily. Some of whom he meets on the worst day of their lives; all of whom are inclined to try to push him around.
Lestrade has found some way to consistently push back without starting a pissing contest biology would prevent him from winning. And his divorce has been final for a couple of months. He's not a bad looking bloke. Broad shoulders, strong hands. Graceful.
John tilts his head, feeling the hint of a smile curl one corner of his mouth. Clever, certainly. John has always gone for smart. Though his caseload is heavier than Sherlock's and John's not sure how willing he would be to take a few days off on such short notice.
All the more reason to make a moment to ask, then.
He realizes he's been caught staring, that Sherlock had glanced up to look for him. Ready for "Come on, John!" he pushes off the wall. But Sherlock doesn't speak; the bridge of his nose has wrinkled. Lestrade turns to follow his gaze and John momentarily ignores Sherlock in favor of giving Lestrade a tiny shrug and a quick grin. No mistake: a calculated choice.
Sherlock's eyes narrow and he says something to Lestrade in a voice pitched not to carry. Lestrade looks back at him, eyes widening, then at John. He doesn't know exactly what Sherlock said, but he can guess, so he gives Lestrade a nod and a little shrug in the brief interval he has before Sherlock has borne down on him less like the wrath of God than a toddler in a strop. Intriguingly, Sherlock doesn't speak to him; he sweeps silently past and out of the room. John, naturally, follows.