This is my first attempt at a Sherlock piece, so if things are a little rough forgive me. Since I believe in only writing for the fandoms you know inside and out, I've tried to immerse myself as much as possible in the episodes before writing this but if I've messed up canon details or anything please feel free to point them out (gently, if you don't mind).

I realize that this has been done over and over again, but I wanted to give a go at the "John has nightmares" idea, so here it is.

Summary: It is the first night in 221B, and neither new occupant can sleep following the events of A Study in Pink. John paces, plagued by nightmares he cannot shake, and Sherlock becomes curious and slips into scientist mode. John/Sherlock friendship bonding, a bit of character study. NO slash.

He sits on the edge of the couch, fingers steepled in front of him. His eyes are fixed on a book lying face-down on the floor, pages bunched against the thin rug. It is an old book, a little dusty, and the binding is cracking down the middle. It protests its irreverent position on the floor, but he does not notice.

Sherlock Holmes is quiet. He does not move, he does not blink, and he hardly seems to breathe. It is late, and the old flat creaks around him in the quiet of past-midnight. Somewhere upstairs his new flat-mate is sleeping, but John Watson is only a fleeting thought in Sherlock's mind at this hour. He is focused instead on two little pink pills in two little glass bottles, and the pale, grizzled face of a late-middle aged cab driver.

Did I choose right? If I had taken it, did I choose right? His mind is clicking, ticking, humming smoothly, whirring with the precision of a machine, perfectly oiled and timed but lacking something. Lacking the piece of the puzzle required to make it stop humming and whirring and clicking along long enough for him to sleep. He doesn't sleep much anyway, doesn't need it, but he is exhausted now, mentally, emotionally, even physically. It has been a day or two, maybe three, since he slept last, and being centimeters from a chance at death is emotionally draining, even for him.

So instead of sleeping he is here, sitting up at half-past two in a dressing gown and blue pajama bottoms, staring at nothing and replaying the evening's events over and over again in his mind. He is searching for clues, for signs he missed, for something that will grant him peace, for something that will tell him that even had John Watson not intervened, he would still be alive. Searching for something that will tell him that he's not a complete idiot after all, that he wasn't gambling his life to save a bit of pride.

Because right now, he is honestly not sure that he wasn't, and the implications of that are frightening.

It is a quarter to the hour when the quiet of the flat is disturbed by a particularly loud creak from above and then a series of smaller, methodical creaks across the ceiling. A door closes softly, and then water is run through the pipes in the thin walls behind Sherlock's head. The water shuts off. The door opens again, and then quiet steps, the faint groan of a bed-frame, and silence.

It seems he is not the only one having trouble sleeping. This is the third time this same sequence has happened since 10:30 pm, when John had disappeared upstairs to bed. Sherlock's mind jumps tracks for a moment long enough to wonder dispassionately if this is just the way his flatmate sleeps, and if he is going to be woken seven or eight times every night by an insomniac pacing the floor. It is only a moment, and then he is back in the long, narrow room at the college, sitting across from a serial killer with two children and only minutes to live.

It is 2:47 am, and Sherlock has moved to the armchair. He is staring at the ceiling, wondering whether or not he should pull out a nicotine patch or two or if it would just keep him awake when he is really starting to wish he could sleep. His fingers tap out a brisk Mozart Sonata on the arm of the chair, and his eyes flicker repeatedly back and forth from his violin, which sits on the sofa he just vacated, and the ceiling, which has some interesting mold growing in the corner by the door he must remember sample. If he could be sure he wouldn't wake John he would play the Sonata, but the last thing he wants right now is company. He is feeling irritated and moody, and he misses his skull—he needs something to talk to that won't feel the need to talk back.

It is 2:49, and the anticipated accentuated creak comes from above. Sherlock groans aloud. John Watson is, if nothing else, consistent. Every hour he wakes, crosses to the toilet, runs the water, and returns to bed. Thirsty, perhaps? So thirsty he wakes himself up every hour for a drink? Unlikely. This ritual offers him a small distraction, and he turns his mind to it lazily, images of pills and photographs of smiling children still weaving their way through the labyrinth in the back of his mind.

He has hardly begun to formulate theories, however, when the footsteps above continue past where he knows John's bedroom is and towards the head of the stairs. He rolls his eyes to heaven as they begin to descend. He keeps his eyes on the bit of paneling straight above him, but he can see his flat mate's blurry outline out of his peripheral when John emerges from the kitchen.

"Oh, sorry," John says, clearly startled, and clears his throat. "I just saw…just saw that the lights were on, and came down to turn them off."

He pauses, and seems to be waiting for Sherlock to say something. Sherlock offers a grunt. It seems the polite thing to do.

"Um," John says, and clears his throat again. He turns to go, and Sherlock closes his eyes in gratitude. At least John is perceptive enough to realize that he's not interested talking. But then he stops, and asks, "You okay?"

Sherlock grunts again, and swings his head down to stare at John, partly to relieve the crick in his neck and partly to make his communication even more clear.

Go. Away.

John seems to get the message, because he looks a little embarrassed and offers a slight nod.

"Right then," he says. "Right."

Sherlock takes him in, then, because his mind is still on the is John Watson a dehydrated insomniac? problem, and why lose a chance to collect data?

What he sees: bare feet (weight still resting more on left leg, favoring right one, habit), gray plaid pajama bottoms (frayed around the bottoms, balled material, a favorite pair) a loose black t-shirt, 24-hour stubble on the jaw and cheeks, mussed blonde hair, (damp around the hairline), and bright, subtly red-rimmed blue eyes.

Just tired? Possible. Crying? Unlikely, not voluntarily, at any rate. Wet hair, tiny beads of water around the left ear, suggests recent washing of the face, not carefully, but hastily, uncontrolled. Bare feet, no dressing gown, this is unplanned, only came down the check the lights on the fourth time he wakes, he didn't notice they were on the first three, why? Too tired, perhaps, more likely he was more awake this time, getting bored of waking up, irritation or anger will make him more alert. So this is not habitual, then, he doesn't always wake up this much, good, but still begs the question, why tonight?

This is running through his head smoothly, observation to observation, and these observations lead him back to the events of only a few hours previous.

He did kill a man. Not a new experience, certainly, but perhaps a jarring one nonetheless. Could be keeping him awake. Nightmares would explain the repeated washing of the face, the involuntary weeping, the increased irritation in a man unable to control his thoughts. What would that be like?

By the time he has reached this conclusion, John is staring at him with a peculiar look on his face.

"If you're through deducing me, I'll go back to bed," he says, scrubbing away the water next to his ear with one palm.

"Hmm? Oh, yes," Sherlock says. His irritation with the man is fading some, but he doesn't quite know how to broach the subject of John's inability to sleep. Easier to let it go. "Fine."

"Thanks…" John says, the word elongated, bemused, and then he leaves, rubbing a hand across the back of his neck and shaking his head. Sherlock spares him a few more seconds thought, and then his head decides that it has had enough after all, and mercifully shuts down. He passes out there in the armchair.

3:58 am. Sherlock wakes to a strangled cry and a loud crash, like shattering glass. He sits bolt upright, the blood rushing to his head as he leaps to his feet, disoriented for a split second before he realizes he's in his new flat and he's has only been asleep for sixty-three minutes. He has only just registered this when there is another cry from upstairs, but this one is very obviously frustrated, even angry, and Sherlock realizes that not only does this quiet, patient, confident ex-soldier have the ability to shoot another man in cold blood, he also has a temper. Something to keep in the hard drive.

He stands torn for a moment between resuming his place in the armchair or venturing up to…to what? Tuck poor John back into bed? Demand he stop having nightmares about the cabbie he killed on Sherlock's behalf? Bring him a cup of tea and tell him it'll all be better in the morning?

He sinks slowly back into the armchair, listening, but all is silent for a few minutes. Then he hears John pad across the floor and the footsteps hesitate once again on the stairs. He descends, and Sherlock waits. The doctor appears around the door frame again, and this time there are obvious tear tracks on his cheeks he either didn't bother to wipe away or didn't realize were there. Sherlock assumes the latter—someone with John's dignity wouldn't approach a practical stranger with any evidence he'd been crying if he could help it. His face is pale, and his eyes look steadily into Sherlock's when he says without preamble,

"I'm sorry. I don't suppose I'm used to a flat mate yet and I forgot myself. Hope you weren't, ah, asleep, and that I didn't wake you with all that. Smashed a mug. Accident. So I just wanted to come apologize if I had woken you up."

"No need to apologize, though I was asleep," Sherlock says, leaning back in the chair and folding one leg at a right angle across the other. "Nightmare?"

"Uh, yes," John says, and his eyes flicker away from Sherlock's now, and he thinks, sore spot. Happens frequently. "Yes, it was." He wavers in the doorway; he seems torn between continuing his explanation and making a hasty retreat. He reaches up with a palm and scrapes it upward over his cheeks, wiping away the traces of tears, and shifts his weight onto his right leg.

"Stopped hurting," he says, tapping his thigh with his fingers. "Ever since that ridiculous thing we did yesterday. Chasing a cab. Can't even remember how it used to feel."

Sherlock allows him the change of subject gracefully. "Mmm, good. Told you it was psychosomatic."

"Yeah, I know."

There is a silence, and John's eyes flicker to the armchair opposite Sherlock. Sherlock heaves a deep internal sigh.

"Sit down, if you like," he says, but he is not quite able to keep his voice indifferent, and John shakes his head.

"Thanks, but I was just…just coming down to apologize," he says. "Thanks." He offers a close-lipped smile and then he is gone again without waiting for a response. For a split second, Sherlock considers calling him back, but the moment passes far too quickly and he is alone again.

His insatiable curiosity gets the better of him, and ten minutes later he stands and follows John upstairs. He walks carefully, quietly down the hall, sticking to the edges in an effort to keep the floorboards from giving him away. John's bedroom is on the left, and he stops outside the closed door and listens.

He listens for a long time, his body completely still, his breathing slow and controlled. He is aware of the time ticking by, but it does not bother him. Most of the time he likes to be moving, to be doing something, to be active and involved in anything and everything. Sometimes, however, the energy that laces his arms and legs and chest and drives him to be here, there, and everywhere all at the same time converts to a tight, hot spot in the center of his brain. It quiets him, controls him, and it is so all-consuming that all his body can do is shut down and wait patiently (or impatiently) for his mind to release the energy it has stolen. It is these moments when he can sit for hours at a time, completely motionless, and enter his Mind Palace or conduct complicated, lengthy experiments or stake out crime scenes in the middle of the night for hours on end.

John's bedroom has become a crime scene, an experiment, and Sherlock is content to wait until it plays itself out, because once he knows what exactly is keeping his flat mate awake another little puzzle piece of what makes John Watson will fall into place. When the man had first walked into the laboratory at St. Bart's, Sherlock had seen him, observed him, deduced him, and thought that that was that.

But John had been full of surprises, and in that first 24 hours he had looked at the flat, been confronted by The Arch-Enemy (and made his surprisingly-quick loyalty known), helped chase down a cab, decided to move in to 221b, had his new flat invaded by a "drugs bust" on his new flat mate, had said flat mate disappear, and ended the day by killing a rogue London cabbie.

From turning down a bribe to spy on a man he hardly knew to shooting a man in the chest for the same man, John Watson was not the man Sherlock had thought him to be, and the consulting detective was both strangely touched and incredibly intrigued by how quickly the man had taken a side—his side.

These thoughts and more are burning hotly in his mind when a faint shuffling noise creeps under the door. Sherlock checks his internal clock—it's been a little over an hour since John came downstairs last. Right on cue.

It sounds as if the man is just tossing and turning, now—there are lengthy periods of silence between the sounds of blankets rustling and flannel pajamas rubbing against sheets. Then there is a low, muffled moan, and Sherlock reaches for the doorknob. He feels no guilt at the intrusion of privacy—he is only observing to learn, and there is never harm in a scientific experiment. He eases the door open carefully and slips inside. His eyes adjust quickly to the dark, and he can see a huddled lump under the top sheet across the room. He stays just inside the door and leans back against the frame. He waits.

John's legs move now, a curious jerking motion, and Sherlock thinks, he's running. Another low moan that cuts off in a quick intake of breath. John goes still again. Then, barely seconds later, he whimpers deep in his throat. Sherlock blinks. He feels an unexpected twinge of sympathy for whatever the man is experiencing that would inspire such a sound.

Did I do that? He wonders. Did I frighten him that much? Or is it guilt for shooting the cabbie? Is it for my sake he dreams tonight?

"Please…"

It is just a whisper, a mumble, but Sherlock understands because he has been waiting for John to speak, hoping that he would, because right now he has only theories.

"Please…" John says again. He has thrown the sheets nearly off the bed. He is lying curled on his side, black tee riding up a little on his back to expose a pale circle of skin above his pajama bottoms. His head is jerking gently back and forth on the pillow—one arm is flung out in front of him, the other tucked underneath his body.

Without realizing he has, Sherlock has moved towards the bed. He stops near enough that he can see a pale line of sweat around John's hairline, can see the rapid beat of the pulse in his taut neck, can see his eyes fluttering beneath their pale lids.

Please what? he thinks. WHAT?

As if in answer to his question John speaks, and what he says chills Sherlock all the way through.

"Please, God…let me…live."

Sherlock takes a step back, torn between continuing the observations and bolting for the door, but it is too late. John's eyes close tightly; his whole face pinches and then his eyes fly open, and their dusky blue is so dark it's almost black. They are cloudy, and they crease in confusion and fear, and one hand begins instantly to scrabble wildly under his pillow for something that is obviously not there.

"My gun!" he chokes, and Sherlock puts out a hand reflexively.

"No need for that," he says, too loudly, and John seems to register him for the first time. The dark eyes narrow and his face contorts emotively, blazing through shock, embarrassment, and anger in a matter of a second or two. He sits bolt upright, pillow flipping up and onto the floor, and buries his face violently in both palms. He is hunched over, visibly shaking, and in one of those extremely rare moments, Sherlock has absolutely no idea what to do.

Before he can do anything but clear his throat awkwardly, John tosses the crumpled sheets aside and swings his legs out of bed. He does not make eye contact as he strides unsteadily from the room. Sherlock is left standing by the head of his flat-mate's bed in his plaid pajamas, listening to the water run for the sixth time and feeling a chill rise up from the hardwood floor through the soles of his bare feet and all the way up to his chest, where a strange, unfamiliar ache is pounding away at his heart.

Oops. This was supposed to be a one-shot, but it got long. So I'll post part II as soon as it's finished! Hopefully that'll be pretty soon.

Review, please!