"It's fine, let me do it."
John had been halfway through a plate of Five-spice Chicken when he'd realised that the powder burns on his fingers were... well, burns. They hurt. While he was sure that running them under cold water was much too little and too late, he'd gone to the mens room and done it anyway. What he hadn't expected was that Sherlock was going to come with him and stand over his shoulder while he did it, giving a running commentary on what he should do and how he should do it.
It was weeks - months - later when John looked back and saw this gesture for what it was.
"It's no use trying to wash it off," Sherlock told him in that annoying know-it-all way he had. "You're going to need to-"
"Yes, I know." John spoke through gritted teeth. "I've done this before."
"How many times?"
It was a few seconds before John registered the question; when he did, he shook himself slightly. "Sorry, what?"
"How many times have you done this before?" Sherlock insisted.
At this, John twisted the faucet off, reached out for a paper towel, and turned to face him. But there was no malice in Sherlock's grey eyes - only a childlike curiosity. John thought back to earlier that night, and the look on his face when he realised that loudly wondering why a woman would "still be upset" about her stillborn child was A Bit Not Good.
He wasn't trying to be rude. Sherlock just didn't have much of a grasp on basic social interactions.
"I don't think I want to be talking about this with you in the mens," John finally told him, a little stiffly. "You shouldn't have come in here with me anyway."
"Because you... just don't do things like that..." John shook his head, giving up for the time being. It had been too crazy a day for him to explain to someone - a grown man, a genius, and someone he'd met yesterday - why you shouldn't hover over people in a public toilet. Even if they only happened to be making a half-arsed effort to treat powder burns in their fingers after they'd shot someone dead...
"That's your phone," Sherlock said as a high-pitched trilling sound emanated from John's left jeans pocket.
"Yes, I know." John flicked the crumpled paper towel into the waste-paper basket beside.
"It's your sister," Sherlock prompted him impatiently. "Are you not going to answer it?"
"Not if it actually is Harry, no. And how would you know who it is?" John pulled his phone out of his pocket, sliding the cover up and checking the incoming number.
"John, try to keep up." Sherlock sounded heartily disappointed. He hoisted himself up on the countertop next to the sink, legs dangling cheerfully, as if he was the world's tallest six-year-old. "It's just past one a.m. Four different television channels have a brief five-minute news bulletin at that hour. The story of the dead cabbie has just broken out, and your sister's now convinced you're lying dead on the linoleum in one of the classrooms back at the college."
"Yeah, well, that'd serve her right for not listening to the news properly," John muttered. "She'll live. I'll call her tomorrow."
The phone rang out; there was a short silence and then the muffled ping of a voicemail alert. Sherlock looked briefly disappointed.
"Oh, don't." John smiled wryly. "Don't start lecturing me about Harry."
"I wasn't going to lecture you." Sherlock sounded vaguely offended.
"Everybody else does."
Sherlock snorted in contempt. "I," he said haughtily, "am not everybody else."
No. No, you're certainly not, I think we can agree on that.
"Well good, 'cause you're not in a position to talk about playing nice with family. I've already heard about Christmas dinners with your brother," he said.
"And I suppose," Sherlock huffed, crossing his arms defensively, "Saint Mycroft wants recognition from the Vatican for tolerating me. You've met him. How pleasant do you think he makes Christmas?"
"I'll bet it's never boring." John looked down at his hands again. So far as he could tell, both of them had been perfectly steady since he'd first met Mycroft. And a good thing too. I don't think Sherlock realises how close that bullet came to his own shoulder... "Anyway," he said. "It's getting late."
Sherlock shrugged, as if the idea of quarter-past-one in the morning being 'late' had only just occurred to him. "Yes," he said blandly, sliding off the countertop. "Yes, I agree. Let's go home, then."
Perhaps it had been early in the evening - before the chase after the cab. Maybe it had been during the drugs bust. John was never sure later, but it didn't really matter. What mattered was that at some point during that night, he'd come to realise that Sherlock Holmes was his flatmate and that 221B Baker Street was home.
A/N- If you're wondering what happens next, see the one-shot on my profile, Powder Burns. :)