Disclaimer: The case was stolen from the movie Untraceable. There's also a small wink to Dexter fans in there; obviously I don't own that either.

On a normal day, the kitchen of 221B Baker Street looked like a fusion between a kitchen and a laboratory. On that night, the kitchen was barely visible under all the lab equipment Sherlock had managed to scatter on every surface. Lestrade's team had left an hour before with Peter Howarth's body, but Sherlock had had time to collect every bit of blood, fibre, hair, saliva, nail, and skin sample he needed. He was currently having the time of his life examining every piece of potential evidence closely, trying to find something – anything – that would lead them to the killer. John was sitting on a chair, watching Sherlock work with tired eyes, his head heavy on his forearm resting on the small table beside three beakers, a petri dish, and a couple of chopsticks.

Sherlock was aware that he was showing off a highly competent side of himself. Yes, he was doing the same thing Anderson would eventually do, but not only was he was doing it in a kitchen, he was also doing it quicker and better. John wasn't watching, though, and that was unacceptable; it wasn't everyday Sherlock had the opportunity to demonstrate how adept he was at things other than deductions, and John shouldn't have missed any second of it. But John was exhausted, and it was a matter of minutes before he fell asleep at the table. Sherlock was tempted to shake his shoulder and suggest he went to bed, but he was almost done with the tox screen, and he wanted John to be there to hear the results.

"John?" he whispered when the test was done, but John didn't move.

"John!" he repeated louder as he delicately put his hand on John's arm.

With a groan, John opened his eyes and looked up at Sherlock with heavy, drooping eyelids.

"Did you really let me fall asleep in this position?" he asked, frowning.

"I have the blood test results," Sherlock said, ignoring the question.

Suddenly, John was awake. He straightened up, ran a hand through his hair, and Sherlock waited until he had his full attention to show him what he had learned.

"I discovered traces of etorphine hydrochloride in his blood. I'm not surprised by his use of a sedative; we didn't find any trace of struggle in our search yesterday night. Etorphine hydrochloride – or M99 – works so fast Howarth probably didn't have time to struggle. Are you familiar with that particular sedative John?"

"Not really, no. I've heard of it, of course," John said, and Sherlock could practically see the wheels slowly turning in the other man's head. Sherlock willed John to reach the same conclusions, as parents will their child to talk. John hadn't disappointed him yet, and he didn't want it to happen now.

"Isn't it used on animals?" John finally asked, and Sherlock nodded encouragingly.

"An animal sedative, that means only veterinarians can access it legally," John said, his smile widening.

"Veterinarians, animal control, or circus workers, yes," Sherlock confirmed, and John thought for a moment.

"So we're looking for someone who has access to that drug, it should considerably shorten our list of suspects," John said, sounding thrilled.

Sherlock wanted to kiss him. John had once again proved he was brilliant. Not as brilliant as Sherlock, very few were, but intelligent and perfectly capable of solving puzzles alone.

"You're right John, the proverbial haystack has gotten considerably smaller," Sherlock said as he texted Lestrade to tell him his team had to start searching in a new direction.

"You should go to bed, we may have a big day tomorrow, depending on Lestrade's team's ability to do proper research," Sherlock said.

"Not if you need my help. Do you need my help?" John asked, and Sherlock wished there was something to do, anything.

"Nothing we can do until morning, get some sleep and I'll wake you up if something happens," Sherlock said.

"Aren't you going to sleep?" John asked.

"Maybe."

"Goodnight, then," John said, and he got up the stairs to the room that was his for the time being.

It was pleasant to see him walking without limping. Sherlock didn't know how long it would last, but he was ready to come up with other ways to get rid of the psychosomatic injury if it ever reappeared in the future. Except he wouldn't be the one dealing with it by then, he thought as he slumped down on the sofa. He busied himself with the case for a while, but the chase across the city had been tiring, the part of the duvet his face was pressed against smelled like John, and he was quite comfortable, so it wasn't too long before he fell asleep.

:::

When Sherlock woke up, sunlight was flooding the flat; from the look of the light, it was somewhere between seven and eight in the morning. There was an unusual noise coming from the kitchen, someone was handling the kettle and whistling a song he didn't recognise. John was awake, then, and he sounded quite cheerful. Sherlock was surprised he had slept so late; he usually didn't enjoy lazy mornings when he had a case. He blamed it on the duvet and its enticing aroma, which was unfortunately gone by then, and he got up to check his phone. Once he confirmed that he didn't have any messages or missed calls, he made his way to the kitchen to see what John was up to.

There were two empty mugs on the worktop, two slices of bread in the toaster, and John was leaning against the fridge while waiting for the water to boil or the toast to be ready; whichever would come first. He was still in his sleeping attire (old grey sweatpants with a white cotton undershirt), his feet were bare, and his hair was tousled; he looked like someone who belonged right here, in 221B Baker Street. For a moment, Sherlock felt the pang of envy when he pictured John in Mycroft's too large kitchen, followed by a rush of anger directed at his brother who probably wouldn't be able to appreciate how unique and engaging John was. However, it all went away when John turned around, spotted him, and flashed him a wide smile that turned into soft laughter.

"I don't think I've ever seen a suit so ruffled," he said, and Sherlock laughed with him because it felt good, and because his suit did look awful.

After a cup of tea and a piece of toast that John practically had to force down his throat, saying he hadn't eaten in over twenty-four hours and that he was being ridiculous, Sherlock had a quick shower. He changed into a pair of ironed trousers and a clean, blood coloured shirt. John was in the armchair of the sitting room when Sherlock came back down.

"That's a good colour on you," John said, and Sherlock felt himself flush slightly, but his skin was still red from the heat of the shower, so he was quite certain John couldn't notice.

It was John's turn to use the bathroom and get dressed, and while he was away, Sherlock received a text message from Lestrade.

Another victim.

On our way.

Sherlock bellowed for John to come down, and when he did, he still had shaving cream under his chin. With a smile pulling at one corner of his mouth, Sherlock got closer until he was standing well into John's personal space. John looked up as Sherlock used one of his long index fingers to slowly, deliberately remove the excess cream. Before John could form a protest, Sherlock had disappeared into the kitchen to wipe his finger on a tea towel. Less than a minute later, they were catching a cab and heading to Scotland Yard.

When Sherlock and John arrived, Lestrade was speaking animatedly to Jim from PCeU. The DI's computer was open on the desk, and the web browser showed the Internet Killer's website. Sherlock ignored the two men in the office, and he sat on the other side of the desk, gesturing for John to take the seat beside him. Then, he turned the computer around so they could watch what was happening on screen.

The live feed was back, and a man was tied up by his ankles and hanging from the ceiling, with his hands tied to the floor. He looked distressed, but not as much as Peter Howarth had looked in the early stages of his kidnapping.

Eventually, Lestrade and Jim were done talking, and they turned to greet the two men who had arrived a few minutes earlier. The DI looked exhausted, but his voice was still warm, and Jim couldn't seem to stop shooting not so subtle reverent gazes at Sherlock. They barely had time to greet Sherlock and John before Sally walked in. She said hello to her boss and Jim before turning to the pair of men sitting in front of the laptop.

"Hello Freak. Hello Freak's…fan," she said as a way of introduction.

John frowned and looked up to offer a forced smile, but Sherlock ignored her and continued to study Lestrade's laptop, hoping to see something that hadn't been there before. It didn't look promising.

"Donovan, do you have any leads?" Lestrade asked.

"That's why I was coming in, actually. We managed to track down everyone on the M99 authorized buyers list, except one Patrick Bateman."

"Track him down, we need him. Anything else?"

"No sir," she answered before leaving Lestrade's office.

Sherlock was animatedly discussing Patrick Bateman with Lestrade, but John wasn't paying attention anymore. He had his eyes fixed on the screen, as if hypnotised. It wasn't long before Sherlock noticed, and he stopped listening to what the DI was saying to give his full attention to what John was doing. His lips were moving, his brows were furrowed; Sherlock had never seen him in such a state of concentration.

"Did you see something?" Sherlock asked.

"Can you zoom in on the eyes?" John asked, and Sherlock hit the CTRL and + keys on the keyboard until they had a better view of the man's face.

His eyes never leaving the screen, John asked for a pen and a piece of paper, and, when Sherlock provided them, he seized them and started muttering unintelligibly.

"John, what is it?" Sherlock asked.

"Morse code. Right eye dots, left eye dashes," he said, and he started writing, his eyes never leaving the screen.

Sherlock could see the man on the screen blinking feverishly, his left eye remaining closed significantly longer than the right one. To the untrained eye, it looked as though he was twisting in pain, but John had seen under the surface, he had spotted what Sherlock probably wouldn't have recognised. For the next minutes, John kept muttering to himself while scribbling on the piece of paper, often crossing out a letter and replacing it with another one.

Sherlock watched, almost transfixed. He was utterly fascinated by the sight of that man who had looked so terribly ordinary only three days ago. Was it only three days? It felt much longer. So much had changed since he had first laid eyes on John at the train station, it felt as if his whole brain chemistry had been altered; he could barely think anymore. Usually, the cases occupied his whole mind; it was effortless, and everything disappeared to make way for the puzzle at hand. Now, obviously, there was the case at the front of his mind, but there was always a part of his brain thinking about John; about what he was doing, what he looked like, what he was thinking, and what to do to convince him that Mycroft wasn't the best Holmes brother for him.

"It's an address," John said, and he handed the piece of paper to Sherlock.

Sirens blaring, Lestrade's team drove off in the direction of the address, Sherlock and John following in a cab not too far behind. They were at least thirty minutes away, so Sherlock decided to use that time on something worthy: watching John. However, it wasn't long before John noticed and turned to look at Sherlock with quizzical brows.

"What's wrong?" he asked.

"Nothing is wrong," Sherlock replied, and he paused before adding, "what you did in Lestrade's office, that was good."

"Part of military training," John said, shrugging, before turning his attention back to the window, making it easier for Sherlock to observe him.

John was stressed, that was obvious. He kept tapping his fingers on his left knee, and he was licking his lips even more often than usual. He was so transparent, his emotions worn on his sleeve for the world to see. It should have been annoying; it was a flaw, a sign of weakness, but Sherlock was surprised to find that it only entranced him further.

When they arrived at the house, Sherlock immediately noticed that the year of construction seemed to fit. He and John dashed out of the cab, but were stopped by Lestrade who was briefing his team and sending them inside. He forbade them to enter the house until it had been secured, so Sherlock had a look around the lawn. There was a particularly flattened patch of grass in front of the house, and Sherlock recognised it as a sign of struggle; the man had been conscious when he had arrived, which explained why he had seen the address.

Sherlock waited nearly five minutes before disregarding the DI's orders and entering the house, but that was only because there were things he needed to examine outside the house. John followed with a sigh and a roll of his eyes. The house was already swarming with Scotland Yard officers who were looking through doors, securing rooms, and making their way downstairs where, if they could trust the video feed, the murderer was. They immediately found the stairs, and they made their way down to the basement.

They were too late. The man was dead, and the murderer – whoever he was – had left the house. The dead man was still hanging from the ceiling, an arrow piercing his chest, and blood slowly dripping onto the floor. Sherlock didn't waste any time, he pulled two pairs of latex gloves out of his pocket, handed one over to John, and got closer to the dead body. Anderson was on his way, so Sherlock had very little undisturbed time ahead of him, but he intended on taking advantage of every minute. With John's help, he observed the dead man's body, collected blood, saliva, skin, and hair samples, and dirt from under the nails to analyse later.

When Anderson arrived, they left him alone with the dead body, and Sherlock started exploring the crime scene. Evidence bags, tweezers, and a small magnifying glass came out of his suit pockets as naturally as if they were handkerchiefs. The basement was so large and was filled with so many things Sherlock wanted to examine more closely, he eventually ran out of pocket space, and he had to use John's. However, John was rather reluctant to having what he described as gross stuff shoved down his coat pockets, so Sherlock had to be ingenious and act quickly when John was distracted. Before he knew it, John had three dead bugs, two different types of mould, and a bag filled with damp soil in his coat pockets. When Sherlock tried to sneak what looked like ashes down his back jean pocket, John really had to put his foot down, and he grabbed Sherlock's right wrist.

"Don't even think about putting that in there!" he said threateningly, but with playful sparks in his eyes.

Sherlock tossed the evidence bag in the air, caught it with his left hand, and successfully managed to shove it down John's other back pocket. John's clear laugh echoed through the basement, soon joined in by Sherlock's deeper one. The policemen turned around to look at them, their disapproval clearly visible.

"Gentlemen, this is a crime scene for Christ's sake!" Lestrade bellowed from across the room.

John apologised, and their laughter dissolved into quiet giggles while they continued to look for anything that could lead them to the Internet Killer.

:::

Later, back in his flat, Sherlock's eyes were glued to his microscope. He was observing the mould he had collected earlier in the basement. The killer had obviously planted false evidence; everything Sherlock had collected came from a different part of London, and nothing could help him identify the person who had killed the two men. Meanwhile, John had ordered too much Chinese food for one person, and he occasionally tried to tempt Sherlock with pieces of delicious smelling pork that he refused every time, but not without a smile that only his microscope could see.

"Do you think he'll do it again?" John asked.

"Of course he will," Sherlock answered matter-of-factly.

"Why are you so sure? He can't go back to that house."

"I know because he's brilliant. He's doing this for me, he's showing off, and he's good at what he does. I don't expect he'll stop until I stop him, or until he achieves his goal," Sherlock said, not looking up from his microscope.

John didn't speak right away; he looked at Sherlock with disbelieving eyes until he couldn't remain silent anymore.

"Well, that's nice. I hope you two will be happy together."

John's voice was chilling, there was nothing left of the playfulness Sherlock had heard when John had tried to feed him some pork. He sounded angry, maybe even a little hurt. Sherlock finally looked up.

"What do you mean?" he asked.

"Two people have died, Sherlock! Do you care about that at all, or are you just interested in the killer's 'brilliant mind'," John asked, marking his last words with angry air quotes.

"Caring about them won't save them," Sherlock said, slightly confused as to why John sounded so angry with him. Surely he didn't care that much about the victims; he had never met them!

"Not directly no," John said and he sounded more riled up with every word he spoke, "but caring drives you forward, it's a motivation. Caring is human! Have you got no heart?"

So this was what it was all about. John was faced with an aspect of Sherlock's personality that he didn't like, and he was either mad at Sherlock for being a cold heartless bastard, or at himself for not noticing it earlier. Sherlock didn't want John to be angry with him; he needed John to realise that not caring for the victims didn't make him any less of a genius. In an attempt to make things right, he tried explaining.

"Don't you see John? I concentrate only on the cases, on the puzzles, that's how my mind works."

"The human lives involved, you don't care about them at all?" John asked.

"No, I don't" Sherlock replied, glad that John finally seemed to understand what he was saying.

But apparently, John didn't understand, and Sherlock was surprised when the smaller man got up from the chair he had been sitting on, grabbed his coat, and took a few steps towards the door.

"Where are you going?" Sherlock asked, confused.

"Out. I need some air, I can't be with you," John answered, and he left, closing the door with more force than was necessary.

For long minutes afterwards, Sherlock looked at the closed door. John was gone; he had left him. It wasn't surprising; he wasn't the first person to storm out of Sherlock's life, nor was he the first one to call him heartless. The sinking heaviness in his stomach, the feeling that he would never be able to breathe properly, that was new. He had been doing so well, John had liked the case, he had been helpful and proud of himself, he had run for the first time in months, he had cooked for Sherlock, and had repeatedly called him brilliant. He had had fun, Sherlock was sure of that, they had laughed together so often, even at a crime scene, hadn't that meant something special for John too?

Sherlock shook his head and tried to focus his attention back on his microscope. It was over now; there was no use wasting precious brainpower on John. After all, their story had been doomed from the start; John was marrying Mycroft, the only thing he had seen in Sherlock was a somewhat eccentric brother-in-law, an addition to his family. He had probably viewed him as someone who would come over for dinner, and would pretend not to notice the two hosts had a quickie before his arrival. Well, John was mistaken; Sherlock would never come over for dinner. It was better this way, he would see John at the wedding, and then never again, it was obviously the less painful solution.

Now, he needed to convince his body that it wasn't hurting.

:::

Two men were waiting for John when he got out of 221 Baker Street. One who was vaguely familiar, and the other he had seen twice before in Lestrade's office. Frowning, he looked at the familiar face of Jim Moriarty from PCeU.

"Hello," John said, surprised to see him there.

"Doctor John Watson. Good to see you again," Jim said, and before John could react, he felt the sting of a needle entering his neck. Then, everything went black.