To begin with, John was very worried about his flatmate Sherlock. He wasn't doing anything stupid, obnoxious, or even absurd. He was just laying on the couch in his dressing-gown, staring at the ceiling.

While to most people, this would be perfectly normal, acceptable, and even understandable behavior, John knew that Sherlock was terribly endangered. He grew easily bored in the absence of cases, and they'd not had one for nearly two months, resulting in him not getting up from the couch or even speaking for five days. The only time he ate was when John had forced his medical opinion on Sherlock, prescribing food and water to the languishing detective. So either he was bored and perpetually counting the imperfections in the ceiling, or he was bored and conducting a sociological experiment on anyone living in the building. There was no way to tell which it was, aside from asking, and at this point, that would be a very dangerous thing to do.

John sighed and continued making his tea. He heard footsteps on the landing, and knew that it was Mrs. Hudson with the mail and pleasant conversation.

"Oh, still laying on the couch, are we?"

Sherlock gave no obvious reaction to the landlady's presence.

"Well, I've brought your mail up for you. Oh! I might have found someone to rent the basement!" Mrs. Hudson was clearly excited about the prospect—so excited, in fact, that she hurried upstairs without a further word. There was a sigh from the couch. John put the mail on the table in the living room, and went out to work.

Nothing had happened in 221B while John was at work, as far as he could tell. He was right. He walked up the stairs and into his and Sherlock's rooms and found nothing changed. He sat down in front of his computer to blog about the day (it was a very short blog), made some tea, and watched a long submarine espionage film from the Cold War. Once the two and a half hour film finished, he flipped through the channels for another half hour before setting down his remote in frustration. He stared at Sherlock, irritated at his apparent lethargy, before deciding to speak his mind.

"For God's sakes, Sherlock, you have to do something!" He waited for a reply, a rebuttal, a look of contempt, anything, but to no avail. He stood up to make certain his companion was okay, but Sherlock rolled over and threw a pillow over his head.

Turning to the mail with a sigh, he stacked most of it in the pile with the overdue bills, and most of the rest in the trash. One envelope, however, caught his eye. It had no return address and no name of recipient, just 221B Baker St, London NW1 5RT, United Kingdom.

"Huh," he said, opening the envelope. A small piece of white something was inside, about the size of a pea. He carefully took it out and held it up to the light.

"Bone," said a voice from the couch. The owner of the voice had returned to an upright position, and displayed casual interest in the object. "Specifically human bone."

"How do you know?"

"Urethane dimethacrylate."

John was conflicted. On the one hand, something had interested Sherlock, which was good for everyone involved, but on the other hand, he was annoyed at the casual genius Sherlock presented.

"Which is what, exactly?"

"Dental filling," said Sherlock, as though it was tremendously obvious.

"So this is a tooth?" John placed it carefully on the table.

"Don't be stupid. It's part of a tooth." Sherlock resumed his staring at the ceiling.

"Obviously!" John sighed. "Why would someone send us part of a tooth?"

"Not interesting," Sherlock told the texturing on the ceiling.

"I'm off to bed."

Ten thirty the next morning—John's off day—and he staggered sleepily into the dining area. He'd had a bit of a nightmare about Sherlock literally dying of boredom and rotting away in front of his eyes, complete with the stench of decaying flesh and the associated insect activity. The nightmare troubled John to the point where he was going to force activity on his friend, even if it meant dropping an agitated ferret on Sherlock's head. However, this proved unnecessary as Sherlock was busy monopolizing the kitchen table with his microscope and the bit of tooth they'd gotten in the mail.

"Oh," was the only thing John's tired mind could come up with. "You're up. That's good."

Sherlock looked up from the microscope, eyes still lacking true sparkle such as they had when he was on a really interesting (to him) case, but not completely dull, either. "Yes," he said simply. "Obviously it's human, because no other species fills their teeth with artificial compounds, not even the psychologically dubious women obsessed with their toy poodles, and going by the wear, I'd say it was someone in their early twenties."

"You can tell that from a bit of tooth?" John asked around a yawn.

Sherlock gave his "it's obvious" shrug. "It's the chewing surface of a molar," he said by way of explanation.

"Can you deduce anything else?"

Looking into the microscope again, Sherlock continued. "They lived in a first world country or somewhere else with good dentistry—the filling shows that—but despite that, or perhaps because of it, they ingested copious amounts of phosphoric acid, probably in cola, and as a result, thinned the coating of their teeth leading to the cavity which required the filling in the first place. Chipping indicates that they either played sports without mouthguards or got in numerous altercations."

"Couldn't the chipping be caused by whatever it was that broke the tooth after death? I am assuming they're dead, going by the fact that the tooth was sent to us."

"He or she probably was dead, but these chips are old—they've been worn smooth over years of eating, whereas these at the bottom of the tooth are still sharp and therefore most likely occurred post-mortem."

At that moment, Mrs. Hudson came up the stairs, followed by a young woman in a bright tie-dye t-shirt and casual slacks.

"Oh, Sherlock, John, this is the person I told you about. Samantha Drake. She's renting downstairs."

"And?" said a distracted Sherlock, making it clear he only wanted to focus on the task at hand and not social interaction. John, however, was a bit more gracious, stepping forward and offering a hand.

"I'm John Watson. You'll have to forgive Sherlock. He's a bit distracted." He shook Samantha's hand. "You'll be staying in the basement?"

"Yeah, that's the plan." She smiled somewhat awkwardly, as though she was unaccustomed to introductions.

"You're American," said John in mild surprise.

"Yep." It was obvious she was distracted by Sherlock. "Hi. Nice equipment." She blinked. "Wait, hang on, that came out a bit wrong. I meant the microscope."

"You're a scientist?" asked John.

"Not really, but photography gets really interesting at three hundred magnification."

"You spent the first year of your life in England?" asked Sherlock, finally looking up. Samantha grinned mischievously.

"No. But my parents watched a lot of British TV when I was little, and apparently when I first started speaking, it was with a British accent. I'm guessing you figured that bit out because my accent's certainly not that of your stereotypical Texan." She brushed her bangs out of her eyes. Her hair was shorter than Sherlock's but longer than John's, and was about the same color as Sherlock's. "Anyway, I need to go furniture shopping, so I'll hopefully see you later." She went back downstairs.

John turned to Sherlock. "That's nice, a new neighbor. Someone to talk to."

"Mm," came Sherlock's reply.

"Anyway, I'm meeting Sarah for breakfast, so I'll see you later."

"Where?"

"I'm not telling you."

"Why not?" Sherlock asked, tearing his attention away from the microscope and fixing his gaze on John.

"Because of what happened last time," John replied. Getting no further answer other than returning to the microscope, John decided it was best if he just went.

John returned to find the flat empty. Sherlock had left in a great hurry, knowing him, and had left his computer open to Facebook. John didn't have an account, so either Sherlock had one, or had hacked someone else's, but going by the username, it was probably Sherlock's.

The door closed, and Sherlock came thundering up.

"You have a Facebook account?"

"Yes," Sherlock said, picking up the laptop. "People love to gossip."

"You. On Facebook. That's…not something I expected." John sat down in the chair.

"You should have seen the reactions I got on Connie Prince's page," said Sherlock with a smirk.

"I don't think I want to know." John picked up a book and opened it to its last location.

"Left molar."

John put down his book. "How can you possibly know that?"

"Teeth are slightly thinner at the front. The outside is more raised on the lower teeth, and the inside is much sharper on the upper teeth, at least in most cases."

"So we're looking for a man who had a left molar filled. There's only a few million of those."

Sherlock picked up his cell phone and shot off a text before staring intently at the tooth remnant. He turned his head in various directions, as if trying to see it from a metaphorically different perspective rather than a literal one. His phone chimed that his text was answered, so he stood up and put the fragment in a small plastic bag, putting it in his pocket. He then ran out of the house, John quickly throwing on his jacket. John had just enough time to jump in the cab before it left.

"Where are we going," John wondered aloud.

"New Scotland Yard." Sherlock continued to stare out the window.

"Why?"

"DNA. If we can match the DNA of this tooth to a missing persons listing, we have our victim."

"Isn't that a long shot? I mean, you can get DNA from hair and saliva, but can you get it from teeth?"

"If the dental pulp is intact, DNA can be extracted. It's being used experimentally in Minnesota to solve arson cases. Heat ruins DNA samples. If they can acquire samples from arson victims' teeth, then teeth that haven't been exposed to extremely high temperatures should be a simple task even the police can handle." He said this in a slightly condescending manner, as if it should be very obvious.

"Oh. Right."

The taxi pulled up outside the New Scotland Yard building, and Sherlock went straight into the building, leaving John to pay the cabbie, as usual. By the time John caught up, his friend was crossly addressing Sgt. Sally Donovan.

"What do you mean, he's on holiday?" Sherlock demanded.

"Yeah, well, some people like to have fun with their kids. Away from town. And you."

"Call him back." Sherlock engaged his stare-them-down mode.

"No." She crossed her arms. Sherlock took a deep breath and angrily threw the bag with the tooth fragment onto her desk.

"Get me DNA results, cross-checked against a missing persons list. And Interpol." He turned and left, shouting "And do it in a timely fashion this time. Wouldn't want a murderer to get away because you're upset Anderson dumped you."

"Um, hello, Sergeant," was all John had time to say.

The instant they returned to the flat, Sherlock sent emails to everyone he knew, asking if they'd had reports of people getting body parts in the mail (this took some time as some emails had to be translated into numerous different languages). After the emails were finished, he picked up the violin and began improvising. The tune was fast and frantic for a while before drifting off into a near-lullaby. John had lived at 221B Baker Street long enough to know that his flatmate's violin improvisations directly reflected his moods. It was best not to interrupt; though, on occasion when they were short of money, John seriously considered calling an old friend who had recording equipment so he could record Sherlock's violin solos and sell them online. If Sherlock's attentions could be diverted, there was no doubt he could be one of England's finest violinist/composers.

The violin went on for hours and hours. Even John's telly programme wasn't enough to drown out the sounds of the musical detective. The manic plucking of the violin-strings came in fits between gentle bowing, the first jolting John out of the sleep the latter lulled him into. This happened well into the night, when the music stopped. Within minutes, John fell into a deep sleep.

Yawning and wondering what Sherlock could possibly be up to this morning, John went downstairs in the vain hope there wasn't anything in the fridge that would make a health inspector panic. He was right, the severed head having vanished literally overnight. God help the poor soul who finds that in the dumpster, John thought. Sherlock was nowhere in the flat, and if he was on the trail of something or someone, he wouldn't answer with any coherence as to his whereabouts.

He was about to put butter on his toast when he noticed something odd.

"Why the hell is there a finger in the butter?" He lost his appetite from that sight alone, and vowed never to eat anything that could be prefixed with the word "mystery" in their kitchen. It was one thing to have severed body parts on the battlefield, but quite another to have them in your kitchen. He slammed the butter dish shut and tossed the toast out.

Damnit, Sherlock, (he texted) I can't make anything to eat in this flat without finding one of your experiments!

He switched on the telly and found a rerun of some old '70s cop show, which he only half-watched. Most of the way through, he received a text back from Sherlock:

Then eat elsewhere.

SH

"Great." He slid his phone shut. "That's just great."

Just then, the door opened and Sherlock came in, sporting a black eye.

"Are you alright?" John stood up in concern.

"It's nothing." Sherlock strode into the kitchen.

"No, it's not—who punched you?"

Sherlock wiped the bruise off with a wet paper towel. "Like I said, it was nothing."

"How..?"

"Basic theatrical makeup. Not hard when you've been an actor." He tossed the paper towel into the sink and went to his computer to check his emails.

"You were an actor?" John really shouldn't have been surprised at any more of Sherlock's hidden talents, but he was.

"Throughout grade school." He stood up and got out a world map. "They gave me the large roles because I was the only one who could remember the lines." He pinned the map into the wall behind the couch (it was the only wall open) and added pins in Moscow, New York, Tokyo, and Guadalajara.

"Why did you need to fake a bruise?"

"Not important. This, on the other hand, is probably the most important thing I can do at the moment." He assumed his thinking position, hands together, head slightly cocked to the right.

Not wanting to sound like an idiot, but also not wanting to be ignorant of the case, John inquired as to the meaning of the pins.

"In each location, someone received an otherwise-innocuous letter containing a bone fragment. Some have been small, like the tooth piece we have; my Mexican contact says that a woman there received an entire patella. Tokyo was a partial C6 vertebra, Moscow got a left capitate, and New York is reporting a portion of pelvic bone. They're running a DNA comparison now."

Sherlock's phone chimed.

"Frank Boone, age 23, resident of Prairie View, Texas. Vanished six weeks ago. Went off to the grocery store and was never seen again." He spoke as he replied to the text message.

"American?" asked John. "I wonder if Samantha knows about it."

"Talk to her if you like—I'm busy." Sherlock had gotten up and gone to the couch, laptop in hands.

"Just because I'm from Texas doesn't mean I hear every little thing about missing persons," Samantha said.

"So you have no idea who Frank Boone is?"

"I do know who he is. He went to my high school."

"But you said—?"

"The assumption was incorrect. You shouldn't assume that I know something like that." She nodded in reproach. "He was an idiotic, ignorant, racist jerkwad." She wrinkled her nose in displeasure at the memory of him.

"You're not sorry he's dead?"

"He's dead?" Though her face was far from shocked, she did register surprise. She bit her lip as if holding back a thought.

"Yeah. Apparently he was dismembered or something and sent all over the world."

"Cool." Then, flushing with embarrassment, she added "Well, not for real life, obviously, but on TV it would be cool." Seeing the look of mild horror on John's face, she said "I watch a lot of murder mystery shows on TV. After a while, you start picking stuff up. It starts to permeate your head. You start seeing innocent objects as murder weapons."

"Like what?" John asked, more to be polite than out of interest. He was getting a little freaked out.

"Anything. Everything. That's probably making me sound a bit freaky."

"Just a bit."

"Sorry. It's a well-established fact that I don't think like most people. Which is good, because most people are dolts." Quickly, she added "Not anyone in this building, obviously, but where I came from it was certainly true. I like you guys. You're awesome." She grinned.

Feeling he should get back on-topic, John began a line of simple questioning.

"What was he like? Besides a racist idiot?" He pulled out a notepad.

"The worst kind of redneck imaginable. His vocabulary was limited to cursing and monosyllabic insults, he hated anything liberal or slightly abnormal, got drunk every night since he turned sixteen, went hunting, and was just generally a crude numbskull."

"Did he have any enemies?" John wrote down Samantha's description.

"Pretty much everyone. He was a bully. The only people who liked him were those with Swiss cheese for brains." Samantha was obviously getting riled up about it.

"What about his family or school friends?"

"His parents let him drink five years before the legal limit. Yeah, it's not technically illegal if your parents are there, but the fact that he showed up to every day of high school hungover pretty much proves that some aspects of intelligence are inheritable. His school friends were his drinking buddies. His younger sister went hunting and drinking with them once and ended up in the hospital with buckshot in her arm."

"Did anyone hate him enough to kill him?"

"That's the thing about murderous intent—it doesn't show on the surface. But I don't think I'd be surprised if someone at school did it."

"Did he bully you?"

"A little. But I was often the recipient of unwanted attention. I guess people have this basic notion that if you're a girl with really, really short hair and no boyfriend, you must be a lesbian. The word asexual is not in enough people's vocabulary. I didn't pay extra attention to Frank."

"You don't seem very surprised he's dead." John was standing up, ready to leave, and this was more a personal observation than a line of questioning.

"I'm just surprised it wasn't natural selection. As cold as it sounds, it was bound to happen, if not from a drunken seizure, then from a bar fight or something like that." She rose as he did, and even got the door for him. "Glad I could help as much as I did, but sorry I couldn't reduce the suspect pool."

When John relayed the information to Sherlock, he seemed interested more in Samantha's body language.

"Did she make eye contact with you?"

"I wasn't paying too much attention to that!" John was holding up his notebook.

"You must have noticed."

John thought for a moment. "Yes, she did. A lot. Actually, it reminded me of you. You tend to stare people down, you know. It's annoying."

"Eye contact is important," was all Sherlock said before once again picking up his violin. Three strums in, he suddenly said "Oh, I'm having the other bone fragments sent here. They should be here overnight shipping." Then he resumed his violin-playing.

John had invested in earplugs for this sort of thing specifically. It was four in the morning, and the violin hadn't relented. John slept on, blissfully unaware that his eccentric flatmate was now frantically bowing the poor violin within inches of its life. John dreamed of rowboats and the canals of Venice, while Sherlock never contemplated sleep. John didn't hear a disharmonious sound emitted by the violin shortly before seven in the morning, after which the violin was silent.

Staggering into the living area to prepare for work, John noticed Sherlock sitting and staring at the fire.

"What happened to playing the violin?" he asked sleepily.

"The bow-string broke." Sherlock held up the poor bow with its frazzled ribbon of fine hairs. He threw it down on the floor undramatically.

"Oh," John said, pouring coffee and yawning. The duo sat in silence until John left for work. Passing Mrs. Hudson on the stairs, he bade her a good morning.

"Sometimes living here is like living in a concert hall," she said somewhat grumpily.

"I know what you mean," John agreed.

"Between Sherlock upstairs on his violin and Samantha on her electronic piano, I didn't get a wink of sleep last night." It certainly showed on her face.

"I bought some earplugs. I have extras if you want them."

"Oh, thank you, dear."

John had a typical day at work, treating patients, chatting with Sarah, and generally being glad it was a typical day. Any sense of normalcy faded upon reentering his and Sherlock's flat. Many of Sherlock's experiments had been moved from the kitchen to wherever he could find a place to put them, and left only his microscope, a few petri dishes, and cardboard boxes covered in partial bone fragments. Sherlock was examining these, dripping unknown chemicals on them, and watching the effects.

"Look, uh, any chance of being able to eat at the table tonight?"

Without looking up, Sherlock replied. "I wouldn't think so. Not when there's something so interesting happening."

"What are you doing, exactly?" John moved closer to the table, curious.

"Looking for traces of the chemical used to clean the bones."

"How do you know it was a chemical, not just natural decay?"

Sherlock stood up straight, as if he were asked the most basic of questions. "I've never met a serial killer content with natural wastage as a method of body disposal after immersing dismembered body parts in liquid nitrogen and shattering them. It had to have been a chemical. Besides, I found traces of sodium hydroxide."

John thought for a minute. "So the victim, Frank Boone, was murdered, chopped to bits, frozen, shattered, dissolved in lye, and then had their body parts sent all over the world?"

"So it would seem."

John studied the face of his flatmate. "You're enjoying this. You're actually enjoying the thought of what happened to this person."

"Maybe a bit."

"Sherlock, we've talked about this. You need to at least pretend to care!"

Sherlock stepped back from his microscope and faced John. "Why? What good will it do? The man's already dead, and has been for at least three weeks. I don't see how caring about the atrocities of the crime will make any difference."

How do I explain this to him? "Right. People need to see that you have some sort of emotions. If they don't, they won't want to help you."

"If they expect a reciprocation of emotion, and that's the sole reason for engaging in conversation, that's selfish. I'd rather not." Sherlock's calmness was irritating.

"Friendship! It's called friendship! Just so I know, have you ever had a friend in your life?"

Sherlock looked wounded for a moment. "Yes, John, I have," he said levelly. "Is that so hard to believe?"

"Yes. Sometimes it is." Sighing, John went into the living area and sat down to watch the telly. There was nothing of interest on the news or any other channel, so he rang up Sarah and vented his problems to her.

A three-hour phone chat later, John had calmed down significantly, and went back into the kitchen to apologize.

"Look, Sherlock, I'm sorry—"

"What for?" He stared at the bone fragments.

"For shouting earlier. I dunno, for trying to tell you who to be. It's just irritating sometimes the way you don't seem to care. I just don't understand it."

"I keep my emotions detached from my work. If I mixed the two, I wouldn't be able to observe impartially."

"I understand your reason, but I don't get how you can actually do it." He sat at the chair opposite Sherlock.

"You're a doctor. Did you cry with every patient you've ever lost? Have you ever been so involved in the emotional processes that you couldn't think clearly enough to administer aid?"

John rubbed his face. "Yes."

There was silence for a moment. "Oh." More silence. "You can see why I have to avoid falling into that trap."

"Yes. Yes, I can. I'm just not sure how you can flip off your emotions like a lightbulb."

"I'm not sure how you can't, to be honest." A sigh. "Our minds just work differently."

A few moments passed before John spoke up. "Hey, you want to go to the Chinese place for dinner?"

"Not hungry."

"You haven't eaten in two days, Sherlock. You have to get something in you."

Sherlock sighed. "Must I?"

"I'm prescribing it. My treat."

"Fine. But note that it's under protest."

They stood up, put on their respective coats, and headed downstairs. Upon exiting, they ran into Samantha.

"Hi. Do you guys know of a good Chinese place nearby? I'm starving."

"As a matter of fact," began John, ignoring Sherlock's look, "We were just headed out ourselves."

"May I tag along?"

"If you must," moaned Sherlock.

"Yes," Samantha retorted firmly. "I must."

Sherlock sighed, resigned to his fate.

In the restaurant, the three sat together, mostly due to the fact that all the other tables were taken. It was obvious that Sherlock didn't want to be there in the first place, as he wore a frown and didn't speak the entire time.

Samantha seemed to be studying him. John thought she might be attracted to him (but why? It's not like he was the sort of man to hold your chair or buy you presents or hold your hand!) She kept watching his movements until John, determined to break the awkward silence, spoke up.

"So, Samantha, what brings you to London?"

"Mm?" She chewed for a few seconds. "Well, mostly TV shows, to be honest. I saw it on TV and it looked like a nice place, so I came here."

"That's the only reason?"

"Pretty much," she said, sipping her soda. "I have a bit of an obsessive personality, so when most of my favorite shows are set here, it's a big draw. Okay, more than a bit."

Sherlock looked at his sweet and sour pork with disdain. He wasn't hungry.

"That bad, is it?" Samantha asked with a grin.

Sherlock glared at her.

"He didn't want to eat lunch." John picked at his own food, grateful that for once their meal wasn't interrupted by Sherlock running out suddenly.

"And as for me," Samantha said, "I constantly have to set reminders to eat. I forget to eat breakfast and lunch when I get involved in stuff."

"Really? How do you forget to eat?"

"I just get busy and then it's noon and I'm not really hungry, or I say to myself I'll only do one more of whatever it is I'm doing, and then the next thing I know it's four o'clock. It's not a conscious decision."

John looked away. Somehow she'd been staring at him the whole time she was speaking. It was one thing to have Sherlock do it—he was used to it—but their new neighbor? He wasn't consciously intimidated into averting his gaze, but it felt wrong to continue. They sat in silence for another few minutes.

"Um…did I say something? Because I tend to say things that upset people and I don't notice." Samantha looked confused. Sherlock snorted in disgust. "No, seriously, I have trouble telling that sort of thing."