((I've been toying around with the fandom for awhile now, but this is my first attempt at delving into it. Thank you so much to tomchyk, who was kind enough to read over my work—you rock my socks! Overall, I must say that I'm enjoying it so far, and I hope you will too. Please read and review. ))

Chapter 1: The Unfinished Equation

Sherlock Holmes was very rarely surprised. Especially not where people were concerned. Despite what his primary school teachers had preached, humans were not unique snowflakes. Within two minutes of meeting a person, Sherlock could classify them as neatly as one might classify rocks. As a whole, the human race was so utterly predictable and, at first, his flat mate seemed no exception. In fact, Sherlock had picked him for that particular reason—the last thing he needed was another infernal distraction. And, judging from his preliminary deductions, John Watson would certainly be no distraction. Above average intelligence, soft-spoken, patient, with a past that was so easily written on his face—Sherlock prided himself on selecting such a thoroughly boring companion.

Except John wasn't.

It utterly baffled Sherlock. After nearly four months of living with the man, Sherlock still hadn't pinpointed just what it was about that John Watson that puzzled him. No matter what he did, there seemed to be a critical piece missing – some nugget of knowledge that would tie the rest of the equation together and finally tell Sherlock just what kind of man he was dealing with. Because men shouldn't just fit so neatly into Sherlock's topsy-turvy life; men don't kill for a flat-mate they've known less than forty-eight hours or accept the body parts in the fridge and the chemical stains on the table with little more than an eye-roll and a wry quip. He accepted aspects of Sherlock that no one—not even Mycroft—had ever tolerated. Despite his irritation, his protests , his harsh words, John always stayed, always followed, and Sherlock couldn't understand why. John seemed to veer left when Sherlock expected him to go right, and seemed to go when Sherlock expected him to stay. With each day, the mystery of John Watson became more inscrutable, and Sherlock was determined to get to the bottom of it.

Which was why this particular morning found Sherlock surveying the man sitting across from him, engrossed in buttering his toast. To his credit, John didn't give any overt indication that he was aware of Sherlock's attention, but the crease in his brow might well have been a neon sign to the detective. Most people would have noted John's displeasure and found something else to occupy their time, but Sherlock Holmes was not an average person. He knew he had a limited amount of time before another case appeared on his door-step and the mystery of the flat-mate was niggling at his mind once more. At first John's idiosyncrasies had been little more than a curiosity, something to pick at when John got to be too invasive. But as their time together lengthened, Sherlock began notice the small contradictions in John's personality, the small outliers in John's actions that Sherlock couldn't predict. Eventually his flatmate's odd personality took root in Sherlock's mind, presenting the detective with a tantalizing riddle. However he was only able to focus on his pet project on his downtime. Once the next case started, Sherlock's mind would be wrapped up in the game of it, and though he could (and did) record observations on John, he had little time to truly examine what he'd found.

Sherlock rested his chin on his steepled hands, his gaze remaining firmly on the old soldier. In the early morning light, the grey in John's hair glinted like silver. Though his tanned complexion had long since faded away, his skin had remained weather-beaten and lined, an indelible testament to his time in Afghanistan. Trivial, thought Sherlock scornfully, what else? John hadn't been sleeping well, but not because of the war. His mobile rested on the table beside him and his left hand trembled ever so slightly as he set the buttered toast on the table. Family trouble.

John finally looked up, his offending hand curling into a tight fist. He met Sherlock's eyes and heaved a resigned sigh. "I'm sure you've already worked all of this out," he said, lips thinning around the words, "but I'm waiting on a call from Harry."

Who else? Sherlock thought dispassionately, finally taking a sip of his cooled tea and grimacing. More time had elapsed than he'd thought.

"Spent another night in the park, did she?" he asked, abandoning the tea and opting instead for the plate of bacon and eggs sitting before him.

John seemed to stifle a wince. "She was picked up last night. I am just waiting until she can pass the breathalyzer before I leave to pull her out."

Sherlock replied with some ambiguous noise, hardly caring about Harry's newest disappointment. "Just make sure that you're home in time for the client interviews," he said, regarding the food with disdain. He'd never been a fan of breakfast, but John had agreed to stop needling him about food during cases if he ate three square meals in between.

Another sigh and John leaned back into his chair, which protested with an agitated creak. "Sherlock, this is my family," he said sternly. "You can manage the clients on your own." He glowered at the detective, swallowing his bite of toast. "Besides, you never listen to me anyway."

There was a long pause as the two men silently squared off over the breakfast table. "I listen," Sherlock finally announced loftily. "However, I do not follow advice that I do not agree with."

John snorted, but got to his feet. "Then you don't need me, since you never agree with my advice," he said frostily. "I'll be back in a few hours—try not to run off all of our clients, yeah?"

"I only run off the boring ones," Sherlock replied and closed his eyes, listening to the careful motions of the doctor as he picked up his plate and carried it to the sink. Everything about John seemed practiced, even his gait seemed almost mechanical, as though he had spent so long running, marching, and crawling that he'd forgotten how to simply walk and was still relearning. "Besides," Sherlock added, finally looking back at his flatmate, "they are my clients, not yours."

John scoffed and grabbed his coat from the rack. "Considering how working your cases got me sacked from the surgery, and that I always end up doing the leg work for your cases, I think it's fair to assume that I am officially your partner, which makes them our clients." He shrugged his arms through the sleeves of his jacket and adjusted the collar. "And I, for one, would like to continue eating this month," he fixed Sherlock with a stern look. "So if you would be so kind as to at least hear out the interviews today—"

"Yes yes," Sherlock interrupted irritably, picking up John's mobile from the table and tossing it to him. "Harry's calling."

John blinked, catching the phone with ease. "Right," he sighed. "I'm off then. And Sherlock—"

"I am not going to change my screening methods, John. I refuse to put up with tedium," Sherlock replied stubbornly. There was a long pause as the men regarded one another.

"Actually, I was just going to tell you to finish your breakfast." John said. With a grin and a cheeky wave, he disappeared from the flat, the door clicking shut behind him.

Sherlock listened for the sound John's footfalls to fade away as he jogged down the stairs. Unusual, he thought absently. John never jogs stairs. Sherlock quickly chalked it up to familial worry and dismissed it, stabbing at his breakfast moodily. Nothing new to file away this morning then. Not too surprising, by now there were rarely anything new in between cases. Like most humans, John revealed his truest nature in high-stress situations, so Sherlock's best opportunity to study his companion was in tandem with whatever problem he was offered to solve.

He glowered as he dutifully took a bite of eggs, his foot bouncing an impatient staccato against the tile floor. It looked like he was going to have to find a case after all.

He needed to find a case, anything to give him that next piece to fit in the growing puzzle and he needed to find it soon.