When John walks into the kitchen, Sherlock is flailing around awkwardly, trying to pull something off the back of his head with a hairbrush. John's reminded a bit of a dog chasing his tail.
"Need a hand, Sherlock?"
"I got epoxy in my hair. Don't look at me like that. It was for an experiment."
He bites down his laughter. "Sit down, let me help."
Sulkily, Sherlock lowers himself into a chair and leans forward, letting John pick at the adhesive with his dextrous fingers.
John can't help but notice the steady shift in Sherlock's body language as he gently cards the dark curls with his fingers. It's as if the tension in his body is leaking out through the roots of his hair. Sherlock's posture, usually so poised an alert, is limp and relaxed. Tentatively, John tugs his hair softly, runs his nails over Sherlock's scalp, and is rewarded with a quiet moan.
He stops as he feels Sherlock tense up again. Carefully, he slides his hand out of Sherlock's unruly mop.
"You alright?" John smirks at him, but his eyes are soft and warm. He's not laughing.
"Don't laugh. Feels nice."
"Laugh? At you? Never!" he smiles fondly at Sherlock, who looks mollified. John goes back to stroking Sherlock's scalp and reaches across the kitchen table for the brush.