"John, hurry!" Sherlock pockets his phone, the text promising a particularly exciting and grisly case fresh in his mind as he thunders across the flat.
"John?" No response, which is unusual. He knows John is home, his coat and shoes are still by the door, where he left them earlier.
Sherlock stops abruptly as he flies into the living room, where John is curled up asleep on the sofa. He's about to shake John awake when something makes him pause. They'd been up late for several days in a row, and Sherlock knows that John can't handle the forced insomnia the way he can. Maybe letting John sleep and going out alone is the kindest thing right now.
Gently, he drapes the tartan afghan over his sleeping friend, as John has occasionally done to him when he's finally succumbed to a desperately needed nap on the sofa.
He places a note on the coffee table, where John should see it when he wakes up. No use having him panic for nothing. Sherlock stares down at John's sleeping form, a strange mix of emotions running through him. He never thought he'd find watching someone else nap so interesting.
There will be more cases, he can wake John up next time he needs him. Sometimes, Sherlock realises, it's best to pick your battles.