The violin was crying for mercy by the time Lestrade came knocking. Sherlock saw no reason to bestir himself. The inspector had the spare key. Not that Sherlock had given it to him, but he hadn't raised too much stink since the arrangement came in handy when he wanted to hear from Lestrade without letting him think he was welcome.

Lestrade stopped in the threshold. "Jesus wept! This place looks like a bomb hit it. You have another break-in you didn't tell me about?"

Sherlock lowered the violin and followed Lestrade's gaze.

It was true. The flat was a wrecking zone. Emptied from their filing boxes, papers migrated slowly across the room in cellulose snow drifts. Swept off the shelves, books formed precarious architectures protruding from the papers. Over in the sleeping alcove, Sherlock's clothes hung limply from dresser drawers, the bed had been stripped, and his shoes had been pitched around the room. The furniture looked like someone had been at it with knives. Fresh scores decorated the sides of his bookcases, the legs and underside of the kitchen table, which had been tipped on its side, and the back of one oak chair.

The kitchen area was best written off as a no-man's land.

"I did it," Sherlock finally said, when Lestrade's dogged, hopeless attempts to deduce the scene began to grate at his brain. Of course, now he'd wonder—yes, there went his eyes, flicking predictably down to Sherlock's arm—what Sherlock had been shooting up with lately. Sherlock rolled his eyes. Let him. The only task more laborious than explaining how this disaster derived from a painstaking search for clues to his situation would be explaining that he hadn't cleaned it up simply because he liked it better this way.

At least this mess belonged to him. This flat hadn't changed a whit and yet it wasn't his at all. His shoes pinched his feet in places they hadn't when he'd last worn them. His clothes and bedsheets smelled subtly off. The expectations of his acquaintances were their expectations of a Sherlock who had, somewhere along the way, ceased to be.

In the past three days, he'd toppled one hypothesis after another. Late-night forays into Lestrade's and Stamford's offices had turned up nary a discrepancy. The wreckage of his own flat served as proof that even the stains on his papers and the wood grains on the bloody furniture matched parameters. Not to mention the traces of drugs in his own bloodstream. He'd run those tests yesterday, and found the results particularly interesting seeing as he'd last flirted with cocaine before he'd met John.

The handful of possibilities that remained to him were all so repugnantly unsavoury that he'd spared a precious day to brood over them.

He'd had a drug trip so spectacular that it had altered his personality. He was suffering a psychotic break. Or he was entirely sane...the logical corollary to which was that John had died alone in 2010 of a bomb Sherlock had detonated.

He lifted his violin back to his shoulder and resumed playing. "What do you want, Lestrade?" He suspected he sounded as leaden as he felt, and could hardly bring himself to care.

Sherlock could have brayed like a donkey for all Lestrade noticed. He jerked around when addressed, insensibly grateful to be pulled from his contemplation of the kitchen's dread mysteries. "Kidnapping. Woman disappeared out of a Tesco's while her husband was right there."

Sherlock stopped playing. A cold like fouled river water trickled down his spine. Lestrade smirked into his stare, no doubt convinced that his little mystery had its hooks into Sherlock's curiosity. If only. "Rupert Stiles and his wife Betsy. Owns his own business, which is faltering, and fears the kidnappers' intent is to level a ransom he can't pay." If it had the lilt of a question, that was only because he wished it were one. What it was instead was the final piece of evidence in Sherlock's personal mystery. The rain of conclusions began in his head, logical sequences clattering to the ground around him as if Lestrade had flicked a domino.

"That's impossible." Lestrade kept talking, blind to Sherlock's internal landscape. They always kept talking. "Here, if you've been snooping through my records again-"

"It's fraud."

"-What?"

"It's fraud!" History repeated itself. He knew this case. He'd solved it four years ago. "They've faked it. He's going to burn down his own property." Not a spectacular drug trip. Not a psychotic break. He squeezed his eyes shut, nauseated.

"Yeah, pull the other one," Lestrade growled. Disgust. He was certain now that Sherlock was high. To be fair, four years ago he'd have been right. "It's got bells on. I'm glad you found a sense of humour somewhere, Sherlock, but I haven't got time for arsing about on a kidnapping case. Are you coming or not?"

A hundred sharp-tongued replies rose to Sherlock's tongue. He bit them all back, because it wasn't Lestrade they would've cut, and flogging himself with his own sarcasm wouldn't help anything. He settled for setting the violin down on the coffee table. "Yes. I'm coming."

His uncharacteristic compliance, finally, broke through Lestrade's obliviousness. He took a single step backwards for the door, eyes sharp with a policeman's concern. "You alright?"

"Quite alright." Sherlock could only imagine what showed in his expression, but it made the lines of Lestrade's face twang in response. "I'll be along." He'd never felt less like playing games. For god's sake, just go away and leave me in peace for a few minutes.

When Lestrade had cleared the door, Sherlock dropped onto the battered blue sofa and buried his face in his hands.

This was it, then. Four years in his own past. No idea how he'd got here or how this was possible, let alone how to get back. He'd always thought it a wasteful habit to wish things were otherwise than they were, but right now he would've given a great deal to live in a universe that accepted bribes.

Fear, Sherlock and John had agreed late one mutually insomniac night, was an irritatingly useless emotion outside of certain narrow, immediately life-threatening parameters. And yet here it was, rising into an astringent clot in his throat. The odds were arrayed so far against them. He'd felt the punch and embrace of the explosion, in that instant before he'd stumbled back over his own sofa. He'd known when he pulled the trigger how poor their chances were.

He gathered up his Strad and cradled it to his chest. His consistent old friend, it was a known quantity in his hands, reassuringly unchanged in its relationship to him. The mere act of taking it from its case had been enough to convince him he wasn't in the midst of a fever dream. He knew this violin like he knew London, or Mycroft, or John Watson. It was his in every fibre.

Only that wasn't true, was it? He knew London. He knew Mycroft. He didn't know John Watson. And John Watson didn't know him. And John—his John—might very well be dead.

Sherlock took his time getting to the station, for which Lestrade should be grateful, because if he thought he understood the depths of antisocial behaviour of which Sherlock was capable, he would've had a rude awakening.

By the time he arrived, interrogations were prepping, and Sherlock had regained enough composure to restrain himself from eviscerating (probably verbally) anyone who approached him. He claimed a desk by sitting on it, and from his vantage point watched police swarm about him like so many black and white checkered bees. He didn't give a damn about solving this case—he'd already given Lestrade the answer anyway—but every bit of information he could gather could prove vital in figuring out how to move on from here.

His mind was snapping like a downed high-tension wire. It was a sensation he'd first encountered in those fatal 15 minutes at the pool: not just excited, but desperate. Fight-or-flight adrenaline rush; it was normally John's sort of thrill. Sherlock preferred more cerebral highs, but there was a grubby, primal sort of appeal to it in between the gut-wrenching sense of being cornered. Why did the best mysteries of his life have to keep putting him in untenable positions?

Anderson hadn't gone out yet, but he was already wearing the change of clothes he kept in his office. In the doghouse with his wife again. Barely a deduction, that; he practically lived there. Coburn, who'd retired in 2009, had slipped on managing his diabetes again. His limbs were pale and twitchy. His grandchildren must have been to visit; he never could resist when they offered to share their sweets with him. Donovan was present, pumping out anxiety like a new form of radiation. Her review must be due. If it went well (it would), Lestrade would recommend her for promotion.

What would happen, Sherlock wondered, if he interfered with that process? The right word in the right ear, and she could conceivably spend the rest of her career as a lowly constable. It might make an illuminating experiment...assuming he cared enough about Donovan to hate her that much. Sherlock frowned at his own train of thought. He knew he had it in him to be cruelly vindictive, but if ruining lives were what got him up in the mornings, he'd have gone into Moriarty's line of work.

The Sherlock of a mere four years ago wouldn't have carried out such an act, surely? Had he ever been that cruel? So petty as to destroy someone because he disliked the way they snubbed him? He thought back to college and the circles of kids he'd moved amongst: Sebastian—whom he hadn't destroyed, though he might have deserved it—and all the rest. He'd used them, they'd used him back, and while it hadn't always been friendly or even polite, he thought it had been a fair trade.

Lestrade poked his head out the door from the rear area, shoulders sagging with relief when their eyes connected. Interesting. He hadn't been sure Sherlock would come. Sherlock bounced to his feet and followed him back.

He hadn't meant to rattle Lestrade, but it turned out to be useful. Even off-balance, it took all Sherlock's powers of persuasion to win himself a go at the witness. If the witness had a quarter as much conviction, he might've gotten away with it. As it was, he held up under pressure with all the tensile strength of wet tissue paper—and with a roughly equivalent amount of weeping.

Doubtless Donovan and her cohort would persist in their wilful obliquity and file this as one more exhibit in their case for his monstrosity. The man was no victim, and Sherlock wasn't about to sacrifice making his point to Lestrade just because the criminal turned out to be emotional ly delicate.

The first time through, the house had burnt down. Disinclined as he was to rain havoc on Donovan's inconsequential life, Sherlock still needed to know what would happen if he changed something.

The answer, it turned out, was nothing.

Once he'd finally convinced the good inspector to listen to him, Lestrade rushed off with a few officers and a call to the utilities company. Half an hour later, they'd found the wife and there was nary a sign of residential explosions, cosmic implosions, or unravelling of carefully crafted illusions, space-time, or sanity. Forensics would never even know how much work he'd saved them.

A house was, in the greater scheme of things, most likely a rather minor change, but the potential was gratifying. On the other hand, Sherlock discovered that knowing the punch line reduced the excitement of solving a case to a gruelling slog of evidence collection. Christ, he had to figure out how to fix this. Four years of being able to predict every case and occurrence that crossed his path? He'd go so insane he'd finally take that job Mycroft kept offering him.

Mycroft. Who had yet to shift his overly generous haunches when Sherlock needed that information more than ever. He'd established that this was reality, which meant John existed, but he was off faffing about somewhere in Afghanistan with no inkling Sherlock even existed. The delay was transparently deliberate. His tetchy brother probably fancied it a petty vengeance for all the little slights Sherlock had delivered upon him over the years. Except that for once Mycroft did not have all the facts, and this was the furthest thing from minor.

Naturally, Lestrade chose the worst possible moment to approach. This was beginning to become a bad habit with him. "Walk me through this one more time, will you?" He held out two paper cups like an appeasement offering.

At least the appalling coffee was something to occupy his hands with. He took a sip, and spat it back out. "There's no sugar in this!"

"You're wound tight enough as it is."

Lovely. And now apparently he was being obvious. Should he just write it across his forehead? Sherlock would rather have chewed rusty nails than explain that he had more important things to deal with. Judging by his poorly-closeted concern, Lestrade was already primed to meddle. His involvement could only range from inconvenient to disastrous.

He thunked the offensive coffee down on the appropriated desk, ignoring the tarry mess that sloshed out onto someone's half-filled statement forms. "I already walked you through it twice. I can't be blamed if your small mind is incapable of contorting into the necessary logical structures."

Apparently Sherlock was also too obvious in picking a fight, because Lestrade's mouth flattened but he killed off his temper with a thoughtful sip of his own coffee; barely drinkable even with sugar, by his grimace. "Look." The hand he pushed through his hair only enhanced the silvery hedgehog look he was sporting. "Look. I suppose it's not really my place to bring this up. But. You seem...odd, lately. Even for you. Are you...in any kind of trouble?"

No, it's not your place, Sherlock wanted to snap. Starting a fight on that note would've been child's play, but Sherlock would've preferred to bite off his own arm than discuss the empty space he could feel looming just past his left shoulder.

"If you were any more wooden, Lestrade, they'd be using you for a sawhorse." Lestrade was worried. That didn't jibe with Sherlock's memory. He recalled occasional rows, and two threats to haul him in for possession, but the emotions driving those had been primarily disgust and exasperation. Then again, three years ago, he would have removed Lestrade's head for trying to get chummy.

Knowing the man as he now did, he understood that alienating him wouldn't stop him from getting underfoot if he decided Sherlock needed help. Besides...an evening came back to him, going over records in one of the conference rooms, when John had told a war story that had Lestrade in such stitches he'd spat tea on his paperwork. Sherlock had laughed till he'd nearly tipped his chair over.

He held himself rigid for a moment, then let his shoulders fall, let some of the aggression bleed out. "Let me see your coffee."

Lestrade frowned, puzzled, but passed it over.

Sherlock drank off half of it, then handed it back. "Yes, much better now." Lestrade's gaping shock was so precious that Sherlock couldn't help grinning. "Any further questions?"

One of the Detective Inspector's best qualities was that he recognized when he'd got in over his head. "No. I suppose...you're good then."

Sherlock watched him beat a prudent retreat. He'd never teased Lestrade before. The man had no defense. As a tactic for fending off meddlesome do-gooders, it was a roaring success; he was a bit startled to find it had the side-effect of lifting his mood.

Or maybe that was the sugar. Either way, it preserved Sherlock from the temptation to violence till he managed to get home.

He opened the door, threw his scarf and coat over the lamp, and discarded all other concerns to the wayside, because there was a manila envelope resting on his sofa.

He knew what it was. Unmarked and thin, it hadn't been there when he'd left; and of the three people who could access his flat and didn't want him dead, his landlord wouldn't leave him an envelope and he'd been with Lestrade.

The contents consisted of three sheets of A4 paper. Not a complete record; a brief summary of a military officer's current status. Mycroft's answer in 'yes or no' form.

Captain John H. Watson, Medical Officer, 16 Close Support Medical Regiment, Royal Army Medical Corps

Currently stationed at Camp Bastion, Helmand Province, Afghanistan

Due for deployment March 1, 2007, Operation Achilles

Real, Sherlock's mind sighed.

But of course he was. That'd already been established. If his next breath came a little easier through the knot around his trachea, it was just maudlin sentimentality. With the documentary evidence in hand, however, Sherlock couldn't quite bring himself to mind.

It was 02:19 by the mantelplace clock. That made it February 23. Six days before the British Army sent John off to get lost in the remote hinterlands of a backwater country.

It was enough. Sherlock already knew how to do it. But the question he'd deliberately avoided asking finally forced its way up through his thoughts: What good would it do?

The answer supplied itself just as readily. None.

It felt like having his chest cracked open. Facts didn't change because you didn't like them. Denying them was a waste of energy. Accepting them cleared the mind of clutter. He had rare insight into the reasons someone might reject them anyway.

He threw the pages down on the sofa, freeing his hands to scrub frantically at his hair while he prowled the room, kicking books and shoes carelessly out of his way. Assuming he made his way to Afghanistan and tracked down a stranger who wore a face he loved, he could...what? Convince him to desert? Follow him around a warzone like a lovesick puppy? Explain that one day, John would be the man to prove that Sherlock Holmes had a heart, not to mention periodically saving his life and warming the abandoned caverns of his self with a companionship Sherlock would freeze to death without?

John didn't know him. John was a dedicated military man. He wouldn't be released from service for over two years yet. He was nevertheless still John in his essential core, as perfectly Sherlock's complement as if he'd been constructed solely for the purpose. Sherlock didn't doubt he could sway John to choose him over his commission if he put his mind to it. But even if the RAMC accepted his resignation, what would it get them?

A John who was years too young, his life irrevocably altered. A John who might come to regret his choice, who might be stranded with a Sherlock who didn't know him. Who wouldn't be shot in 2009 by an insurgent. A John who, if all went as poorly as possible, would know Sherlock for four years instead of one, who might not die in an explosion in 2010.

The pointlessness of it burned through Sherlock like acid, but his bones ached as if they'd had pieces cut out. He'd never believed in emotion over reason, but then he wasn't the man he'd been before he'd met John Watson.

Six days, and he knew how to do it. It was idiotic, probably frivolous, unforgivably selfish, and a touch mad even for him, but all he had to do was reconstruct himself circa 2007 within the next six hours.

Notes:

Poor Sherlock. He always misses something. ;)

FYI for those who're interested, I'm seeing John as a career officer. This means he's in until he resigns or retires (pre-retirement resignation is not easy; the military doesn't like letting go of its officers).

British Army tours of duty (i.e. warzone deployment) typically run in six month rotations. Halfway through, you're given a one-week furlough, which can be rescinded if your superiors decide they need you where you are. You can be put on back-to-back deployments, with a six-week "break" in between (break in the sense that you're stationed somewhere friendly, rather than in a combat zone, but not necessarily England).

If John wrapped up med school in his mid- to late-20s, and had enough time to end up—if we go with ACD—a Captain, he probably signed up shortly after he got his medical license. If he was in the military for 5+ years, he would've seen multiple tours in Afghanistan/Iraq. It seems reasonable to figure he spent a total of two years of that time in a combat zone. Where he is in his current rotation, I never bothered to figure out because, as you'll see, it's not going to matter.