DCI Lestrade has seen Sherlock's face in almost every conceivable expression. He's seen him scowl, and snarl, and stare more intently at a corpse than he ever has at anything living. He's seen him ignore everything for days on end, and has come to breathe a sigh of relief whenever he sees the euphoric gleam in Sherlock's eyes, because it means he's occupied, and the closest thing Sherlock Holmes can be happy.
And he remembers the darker days, when he would hold the boy the man used to be as he came down from the high, shaking and sweating and incoherent. When he first took him home from the station, listening in wonder to the stream of information that came from the drug addled lips, as sweat poured of his body and his eyes glazed with whatever crap he'd been pumping into his veins that week.
He thanks God daily that He never gave him Sherlock's mind.
But he's never seen him smile, and this worries Lestrade, more than he will ever let show. Oh he's seen the man smirk, and sneer and fake it so many times, because there is ice between the world and Sherlock Holmes, a thick, impenetrable barrier to keep the world, and all its trivialities, as far away as possible. But it worries him, and it worries him how much he cares, that the man never seems happy. Not just high on the thrills of a case, but really, truly, honest to god happy.
It keeps him awake sometimes, as he lies by his wife and listens to the sounds of silence. He supposes any decent therapist would say he was projecting- having no children of his own, he's 'adopted' the man, directing his paternal inclinations that get no other outlet, but sometimes, when he's listening to him rattle off some new deduction that is frankly incredible, whatever Sherlock says, he feels such a pride in him. And prays Sherlock won't notice, because then he'll never hear the end of it.
Lestrade knows, though Sherlock probably doesn't, that the high functioning sociopath thing is only true as far as Sherlock lets it. He keeps this information to himself, because no-one will believe him, not Donovan, not Anderson, especially not Sherlock, but it's true all the same. A sociopath doesn't care if people don't like him. A sociopath doesn't care what people call him, whether he's a freak or a psycho or a murderer waiting to happen. But Sherlock does. Dear God, does Sherlock care.
So when he sees the new man, the Doctor, at the flat and then at the crime scene, he treats him with a certain amount of caution. Sherlock actually seems to like this man, as far as Sherlock likes anyone, and if this man recoils, as people always do, it'll send Sherlock reeling.
But he doesn't. He follows Sherlock up three flights of stairs on a cane, and waits, patiently, for Sherlock to finish looking. And then he calls him brilliant. Twice. And Dr Watson isn't looking, but it's like a light comes on behind those brilliant eyes. It's gone again, almost instantly, but Lestrade sees, and realises that perhaps Sherlock really doesn't know that he worries, or how proud he is. Perhaps the world's first, best consulting detective's high powered perception is fairly limited.
He needs to be told. He needs to be told that people care, that want him to be happy. And the doctor tells him, and puts up with everything, and can even get Sherlock to be civil. Dr Watson probably doesn't notice the change, doesn't notice the smidgen more tolerance Sherlock now has for the stupidity of the general public, but Lestrade does, and it helps it him sleep.
The Doctor can make Sherlock good. It's more than he ever managed.
