Disclaimer: still don't own it.

Sherlock scratched another line under the toxicity readings on the autopsy report. Lestrade had dropped it off that morning, to John's apparent relief as it made Sherlock actually drop his violin and turn his attention to something more productive. It had been three weeks since they'd had a decent case, with only an elderly woman who had misplaced her pearls contacting them through the website. Sherlock had practically reawakened at the Detective Inspector's appearance, snatching the case file and scanning the front page before sweeping from the room and returning fully suited.

The case was definitely an eight, if not a nine; a serial killer, although Lestrade had no idea how they were doing it. Sherlock was now seated in the kitchen, analysing the data before him whilst running his own control tests beside it, peering into his microscope every now and then. There may have been little evidence to go on, but that just made the puzzle a million times more thrilling. Bodies had been turning up for a month, completely purged of anything that could be used to identify a killer or a motive. Well, Sherlock thought with a smirk, it was enough to fool the average person. It shouldn't take more than a day or two to catch the culprits now that Lestrade had bowed to the inevitable and allowed Sherlock the data with which to theorise.

Every victim's body appeared to have been pumped full of water, bleaching the cells and removing all foreign objects from their DNA. This was clearly a professional attempt to destroy valuable data, but what it actually did was allow Sherlock to deduce that not only were the culprits Medical professionals, as shown by the method of purging the cells, but he could also deduce the far wider picture-

"Sherlock!" John called agitatedly from the living room, where a quick glance told Sherlock he was sifting through the clutter on the coffee table, "Sherlock, where's my newspaper? I put it here."

"I needed to test the effects of various chemicals on newspaper ink," Sherlock answered swiftly, turning back to the microscope; John looked about to retort but Sherlock cut across him, "It was for that journalist case; I needed to see whether he was more susceptible than his sister, who was not ingesting ink-press fumes on a daily basis."

"I only bought that this morning!"

"You have a laptop, go online." Sherlock said firmly, in a tone that always seemed to make John sigh in a put-upon way and storm across the room, dropping into his armchair in front of the fire. Sherlock couldn't be sure, but he thought he heard him mutter 'don't even know why I'm not at work."

Sherlock knew why John wasn't at work; he had mentioned in a side comment that John's medical knowledge might come in useful, and of course he hadn't been able to resist calling in sick. It was a stark reminder of why Sherlock kept him, why he had missed him so much when he had needed to pretend he was dead. Could be dangerous.

There was one thing about this case that struck Sherlock as odd. The victims were all homeless; obviously. Even Anderson had known that, although his reasoning as to why was all wrong. They smell and their clothes are ratty was not a viable method of detection. No, what was odd was that they weren't random homeless people; they were all people that Sherlock had…recruited. It couldn't have been a coincidence that his homeless network were the only ones being snatched and killed in such a short period of time.

He flipped to the next page in the file, and immediately froze. A chill crept beneath his flesh, but Sherlock kept his face impassive. It wouldn't do to worry John. Sherlock pulled his phone from his pocket, dialling the all so familiar number, never taking his eyes from the page in front of him. Written in inch high letters, in the centre of the page: IOU. He couldn't be sure, but he was pretty certain that the letters were written in blood.

"John, I've got to make a call." Sherlock explained flippantly, as he strode as nonchalantly through the living room as possible, "I'll be in Mrs Hudson's flat."

"What? Why?" John's head snapped up just as Sherlock put his foot through the door, "Hold on, why can't you speak here?"

"I need to focus and you're thinking too loudly." Sherlock replied waspishly, instantly regretting it as John was bound to get angry, but he wasn't going to take it back. This was important.

"Oh that's great," John responded sarcastically, "So I've taken a day off to sit here and look pretty."

But Sherlock was already out the door and half way down the stairs, placing the phone against his ears as he took the key from under Mrs Hudson's mat and entered her flat. She should really keep it in a safer place, he thought. The dial tone cut off.

"Sherlock! Don't tell me you've worked it out already." Lestrade's cockney tones clambered down the line.

"Lestrade, who else has had access to the case files?" Sherlock snapped, in no mood to deal with idiots; not even the brighter ones.

"It's paperwork, it gets shifted about-"

"Yes but who has had access?" Sherlock demanded, his patience wearing thin. Only two people in the world knew the specifics of Moriarty's taunts, and Sherlock definitely hadn't written that note himself.

"I don't know! Lots of people-it's not like we monitor them. Why?"

"These murders are targeted at me. The victims are all…associates of mine."

"Right, what does that have to do with the files?" Sherlock could practically hear Lestrade dragging his hand exasperatedly over his face, squeezing his eyes closed.

"Someone planted a note in them, they're taunting me." Sherlock explained quickly, ignoring what sounded like John clattering around on the floor above, "If you can't find the mole then we'll just have to solve the case and go from there."

"I'll set Sally on the mole thing-"

"Oh must you?"

"Sherlock!" Lestrade snapped, and Sherlock begrudgingly bit back his next retort, "Now tell me what you've got on the case!"

"I need you to check every import into London in the past three months." Sherlock instructed, glancing up briefly as another thud rattled the floor. What was John doing? Rearranging the kitchen?

"Hold on, we were talking murder. Why am I now checking imports?"

Sherlock didn't stop himself from rolling his eyes, growling under his breath.

"I guarantee that there will have been an unmarked import of narcotics at some point in the last three months." Sherlock spoke as fast as he could, frustrated that he even had to elaborate; Lestrade sounded as if he were able to interrupt, so he ploughed on, reeling off his deductions, "The bodies were purged with water, effectively removing any trace of anything from their cells via diffusion. It was clearly done by medical professionals, with professional tools, as demonstrated by the marks on the victims' upper arms and thighs. What reason could there possibly be for doing this other than to remove some kind of drug or poison? None. But why poison someone if you're only going to remove the evidence? Therefore, the victims were clearly test subjects of some sort, it's the only motive that makes sense. So you're looking for imports of unmarked drugs, the purchasers of which will be medical personnel testing a new narcotic for the ever growing market."

There was a moments silence as Lestrade presumably scribbled notes, and the thuds from upstairs were becoming increasingly more frequent. Sherlock stuck his finger in the ear not occupied by the phone.

"Sherlock, if this is true, what's it got to do with you?"

Sherlock considered telling the Detective Inspector the truth, but instead decided upon a diluted version.

"Whoever wants my attention would need something impressive to get it; I gather that my reputation paints me as difficult to please." He answered shortly, noting half-heartedly that there may have been a little bitterness in his tone.

"Well-"

Sherlock never found out what Lestrade thought, as at that moment a gunshot rang out overhead, and the thudding reached an almighty crescendo, as if someone was charging down the stairs. Sherlock cut off the call and bolted from Mrs Hudson's flat.

"JOHN!"

To his horror, the front door was wide open, the cold air blasting into the house as it rattled on its hinges. Sherlock followed the sound of a car revving outside, but stumbled to a stop as he saw a black van turn the corner, almost knocking a young woman off her bike. He turned on his heel, sprinting up the steps into 221B, taking in the state of the flat. There was broken glass strewn across the kitchen floor, twinkling maliciously in the sunlight, and the papers that had been stacked on every flat surface in the living room had been scattered. Most importantly, John was gone.

After a moment, in which Sherlock propped himself against the doorframe and scanned the damage in a kind of muted terror, clasping his hands under his chin, he noticed the crumpled mass lying at the foot of the sofa.

It must be the shock, he told himself, cursing his slow observation. Sherlock tread cautiously towards the mass, kicking it to the side. The body of a toned man in black, his eyes closed and face lax, sprawled out. Sherlock couldn't help the small pang of pride. John had put up a fight. There had only been one gunshot, John wasn't dead. That single thought was enough to kick Sherlock back into gear. He had another call to make.

Wow this is longer than the rest. I love Sherlock to the point it's ridiculous, so this kind of ran away without me. Nevermind, the strings are pulling together now