A/N: This has been floating around in a half-finished state for six months now...but I finally got off my butt and finished it! No slash, just a severe disregard for personal space. (Which is pretty much canon for the updated Sherlock.)
Disclaimer: BBC owns it.
"Moriarty again?" John asked, watching his flatmate set aside his laptop and add two more nicotine patches to the one already stuck to his arm.
Sherlock shook his head impatiently and smoothed the patches flat with two fingers. "Of course not," Sherlock dismissed. "He requires four patches. Though, admittedly, I expected him to contact me by yesterday."
"Requires four patches? What do you mean?"
"It's a system. Nothing important." Sherlock dragged the laptop back into his lap, signaling the end of the conversation.
John muted the television and leaned forward to prove he was really paying attention. "No, seriously, I'd like to hear. It sounds interesting, given it's you. I thought you didn't believe in systems, anyway."
"Only flawed ones," Sherlock replied automatically, then slanted John a tiny, sarcastic grin before returning to his laptop. "Of course, that encompasses most system, especially government ones, because the minds involved are flawed. However, in my case—"
"I know, your mind is all brilliant and perfect, so your system can't possibly be flawed," John cut him off, only grumbling a little. "Tell me about it, will you?"
The grin grew just a bit wider. Still staring at the screen before him, Sherlock corrected, "Strange as it may seem, John, my mind is imperfect. You're right about the system, though."
When there was no response, Sherlock glanced over and saw John waiting for an explanation. "Fine," he said with an exaggerated sigh. "I always wear one patch between cases, simply to keep myself from going out and getting a cigarette. During most cases, I use two patches so I can skip meals with hardly any side effects—oh, stop glaring at me like that!"
"I'm not glaring," John denied, staring pointedly at Sherlock. "But you should eat regular meals, even when you're on cases. It's not healthy to skip like you do. Your body's going to shut down after a while."
"The patches keep me going," Sherlock continued, ignoring John like he did whenever he started talking as his doctor. "I use two for tame cases, the ones I can finish within a few days but require little mental effort. Three patches are for cases that either are tricky or develop complications. Using four patches is reserved for those related to Moriarty."
"What about five?"
Sherlock shrugged and frowned at the muted television in front of him, seeming distracted. "I've never encountered a five-patch problem before," he replied, then unexpectedly turned and smiled at John. "If I ever do, you can be sure you'll be the first to know. Now turn the sound back on, won't you? This looks interesting."
A month and a half later, John was the first to know. Sherlock hadn't eaten or slept in close to six days because of one of Moriarty's games, and he'd only allowed himself to collapse after he made sure Moriarty's latest pawn was securely locked up. John had roused him long enough to get him home and feed him some leftovers before Sherlock flopped down next to him on the couch for some more sleep. John protested that he should sleep in his own bed, but Sherlock only curled around him and fell asleep within fifteen seconds—thirty, including their brief argument.
John woke the next morning to find Sherlock's eyes staring fixedly at his own from less than an inch away. He instantly jolted back, letting out a mild swear under his breath as he put some space between himself and the detective. "Sherlock, why on earth were you watching me sleep? Not exactly the most pleasant way to wake up, sorry."
"I wasn't watching you sleep," he responded, sounding affronted as he rocked back on his heels so that he was fully sitting on the floor. "I was trying to get you to wake up, but it took a full seventeen minutes. I'm hungry; can you call for some Chinese?"
One blink, then two, and the two statements came together with Sherlockian congruity to make some sense. "You wanted some food, so you stared at me until I woke up?" John asked, checking to make sure he had gotten it right. He sincerely hoped he had not.
"Yes, of course," Sherlock said primly, as if it were only natural. "And it wasn't pleasant for me, either. Your breath smells atrocious in the morning."
John blinked at him again, fuzzily, and muttered, "Not done, Sherlock, not done at all," before sitting up and shuffling off to the phone.
"Sesame chicken for me," Sherlock requested happily, taking John's spot on the couch.
When John returned ten minutes later, he found Sherlock occupying his seat and staring at the laptop screen. A quick peek showed that he was reading John's blog entry for the case before the one they had just finished—not related to Moriarty, fortunately, though it had looked that way for a few days. Giving in, John sat down next to him instead of asking for his seat back.
"Why are you here, John?" Sherlock asked, gaze still locked on the words before him.
A bit confused, John answered, "Well, I finished ordering, and I brushed my teeth. I thought I'd have a seat before the food gets here."
"No, I mean why are you here, John? Here at Baker Street, when it's been fourteen months already since we moved in?" As Sherlock turned to face him, his curls fell haphazard across his forehead, giving him an unexpectedly vulnerable look. "I've had countless flatmates, and they've all been gone within six. I exasperate you to no end—yes, I do, I can tell—and probably even bully you, and you haven't yet moved out. When will you?"
John was definitely not ready to have this conversation so soon after waking up. How had Sherlock gotten so serious so quickly? "I don't plan to, unless something goes horribly wrong," he started, hoping he could make his thoughts coherent. "Yes, you're difficult to live with, but I also like working with you, so it's worth it. And you're a good friend when you're not being annoying, so there's that."
Sherlock shifted the computer in his lap, and John's eyes caught briefly on the patches cluttering his pale arms. He counted five.
"I've been at it for an hour, and I can't figure out when you're going to leave," Sherlock explained in a low voice once he saw where John was looking.
John reached over and peeled off one of the patches. "Well, I promise I'm not going anywhere," he said firmly, standing. "Now take off some more, or you'll be breaking your system."
As John walked into the kitchen to throw the patch away, he heard Sherlock following behind, removing patches as he went.