Disclaimer: Sherlock belongs to ACD, Moffat and Gatiss.

A/ N: It's been three years and a Bachelor's degree since my last fic. Here we go again.

The title is Latin for "Know thyself" – an aphorism attributed to just about every ancient Greek scholar in existence, such as Plato's Socrates.

Supreme thanks to jenamy. for her patience and kindness in beta-ing this fic. You were indispensible.

All mistakes are mine, especially pertaining to medical knowledge.

Nosce Te Ipsum

John awoke to the sound of Sherlock saying his name. Slowly swimming to consciousness, he winced as he felt his neck crick. Bringing his hands up, he tried to rub the sleep away from his eyes.

"Any day now, John." His flatmate's impatient voice came from directly in front of him.

"Alright, alright, what's the rush? Oh..." He opened his eyes to find out he'd answered his own question. Sherlock was seated across the table in front of him, leaning back with his legs crossed. The problem was... they were not at home. Rather, they were in a room he had never seen before.

Right. Kidnapped again. Excellent, John thought. The cotton-wool feeling in his head now made more sense; a remnant of whatever drug he had been given to render him unconscious for God knows how long. At least this time I didn't get knocked on the head with the end of a gun.

"Are you all right?" He asked, looking the detective up and down only to find nothing physically amiss. All in all, Sherlock could even be described as... relaxed. It struck John as odd that Sherlock was not on his feet, trying to find out how to escape from this room. Which was, incidentally, even more sparse and boring than the room he'd been residing in before moving in with Sherlock. He could only see one point of entry, a door in the corner, but no windows or such. The floor was uncarpeted, the walls bare. Quite literally, the only things in this room were himself, Sherlock, the table between them, the chairs they were sitting on and inexplicably, a digital clock.

Oh, and the small camera attached to the ceiling. Somebody's watching us. John mentally patted himself on the back for noticing this on his own. An irritable thought crept into his mind. "Sherlock, is Mycroft behind this?"

Sherlock snorted. "Hardly. This is far too... inelegant... for his taste. And I am perfectly well. The kidnapper slipped something in the milk you bought yesterday, which you put in our cups of tea this morning."

"Right," John said, getting up and walking to the door. "So you think the kidnapper must have switched bottles from my cart when I wasn't looking?" Solid wood without even a handle on the inside, John tried pushing into it with his good shoulder to test the strength. No give. They were locked in.

"Precisely. If Lestrade discovers the milk was tampered, doubtful considering Anderson will be handling forensics, he might think of checking the CCTV footage from Sainsbury's. I don't have high hopes of that happening anytime soon, however." Sherlock craned his neck to look at John. "Are you quite done with the door?"

"Yes, I think so."

"Good. Come sit back down."

John did as he was told, looking closer at his flatmate in an attempt to read him. He would have thought Sherlock would have been ecstatic in this situation, a puzzle to figure out how to gain their freedom, to work out who was behind this. Instead, the curly haired man in front of him seemed content with just... sitting there.

"What's going on, Sherlock? What aren't you telling me?"

Sherlock shifted a bit in his chair. Clad in the suit he'd donned this morning, he may as well have been at a job interview, with John his interviewer.

"As you've probably guessed, I've been awake for quite some time longer than you."

"Yeah, I figured. Your body's built up resistance to drugs, eh?"

Sherlock smirked at this but didn't comment. "Whilst you were asleep, our kidnapper was here, we had a chat."

John was getting more and more nervous by the second. Something was really wrong, beyond the fact that he and Sherlock were locked inside a room with no way out.

"And? Who is he? What does he want?" John paused for a moment. Moriarty. He felt the sudden urge to check under the table for a bomb.

Sherlock rolled his eyes as though he'd read John's mind. "Please. Moriarty is much more clever and imaginative. From what I've gathered about our kidnapper, he's just slightly smarter than the average idiot. He's read your blog and my website and has taken it into his head that he is capable of killing us."

"And," John asked, "is he? Capable of killing us, that is."

Sherlock's nose twitched, something the doctor noticed happened whenever the consulting detective found something to be to his dislike and annoyance, such as anytime Anderson was around.

"Yes."

There was a moment of silence as John processed this. "Right."

"On the bright side, however, only one of us has to die." Having said so, Sherlock took two small glass bottles from where they'd been hidden from John's view and placed them on the table.

"Pills?" John asked, everything slowly beginning to fall into place in his mind, filling him with dread.

"Yes, pills. As I said earlier, he's read your blog. Surely you remember the first case you worked with me on, your 'Study in Pink'?" Sherlock said the title with as much disdain as he had the first time. "Only this time, it is you against me as opposed to me against the cabbie. One pill is poisonous, the other harmless."

"Sherlock, this is ridiculous. We're not actually going to play this madman's game," John protested. He knew the consulting detective loved the thrill of having his life on the line, but this was crazy. This was either Sherlock dying, or him, and John was obviously not comfortable with either scenario.

"Yes, we are. You have to take one pill, and I the other. And we are to do this before the clock turns twelve," Sherlock nodded his head towards the timepiece on the table which read 11:48, "or he walks into 221B and kills Mrs Hudson. And then both of us, presumably."

John leaned forward on the table, his head in his hands. He couldn't believe this. This morning had been normal. They weren't on a case but Sherlock hadn't reached the destructive stage of boredom yet, content with some experiments he'd been running in the kitchen. John had the day off from the surgery and nothing better planned than to perhaps meet Mike Stamford for a drink later on in the evening. Things had been going well enough at 221B that John was considering buying his former classmate a drink as thanks for setting him up with the weirdest man to flat share with in all of Great Britain.

Instead, he was either about to die himself, or watch the greatest man he'd ever met die in front of him.

"There's more," said Sherlock, his deep voice boring through John's thoughts.

"Oh yeah? What's that?"

"I know which bottle contains the poison."

John looked up only to see his flatmate push one of the bottles towards him, his expression giving nothing away.

"I've made my move. It is now up to you if you take the pill in front of you, or the one in front of me. I have to take whichever pill you do not." Sherlock had still not moved from his leaned back position on his chair. "The cabbie was right – this is chess; with pills instead of figurines, of course."

"How is this chess? It's chance," John replied, his fists clenching. A bullet to the head would have been much more preferable than this.

"No, it's not. You're not playing the odds, John, you're playing me," Sherlock said quietly, before glancing at the clock. "You have nine minutes".

"What happens after we take the pill?"

"Well, obvious - one of us dies. He will then inform the police of our location."

"And Mrs Hudson?"

"She is of no interest to him unless we refuse to abide by his rules."

"Is he watching us right now?" John asked, remembering the camera.

"Yes, and he can hear us as well. Eight minutes, John."

"Alright, alright!" John snapped. "Wait, you said you knew which pill holds the poison."

"Yes."

"How can you be certain?"

Sherlock gave him a look. "I'm certain."

"Right." John sat back and there was silence for a minute. He was about to speak, his mind made up, when Sherlock beat him to it.

"You are going to argue that I should tell you which of the pills is poison so that you may take it. Don't bother."

"Sherlock, listen to me! Look at this rationally," John interjected. "If you live, you can get out of here and catch this maniac. You living means you can catch hundreds of other maniacs out there. The world has more to gain from you in it, than me." By this point, John was leaning his elbows heavily on the table, hands outstretched towards his flatmate as he tried to make his case.

Sherlock huffed out a laugh. "Always so ready to throw your life away, John. Joining the army, living with me, and now this. Do you really consider your existence so futile?"

"This is not about me, Sherlock, this is about you! You know I'm right. You're the world's only consulting detective, I'm just an invalided army doctor. You are a rational man, be rational about this, tell me which bottle contains the poison."

"No," Sherlock said again, narrowing his eyes, "and I will not repeat myself. If you are so set on taking the poison, you'll have to figure it out for yourself which pill is which. Six minutes."

"We both know I cannot out-smart you, Sherlock. How do I know you're not going to manipulate me to take the harmless pill?"

Sherlock smiled, only there was no mirth in his eyes. "That depends on whether you think I value your life above mine, Doctor."

John paused at this, peering closely at the man in front of him. He knew that Sherlock was an exceptional actor, well used to putting on a variety of facades to achieve his ends. John had lost count of the number of times he'd seen Sherlock pretend to be a mourning friend/classmate/ex-lover to gain information about a victim. In fact, it had been these instances that convinced John that it was not the case that Sherlock wasn't aware of social manners and skills - he just refused to abide by them. He had observed enough about the common man to pass of as one whenever the need arose – and this worried John.

Because if Sherlock was such a great actor, what made John think he had not been fooled all this time? That Sherlock had not played a character in order to suit his ends even within the four walls of 221B Baker Street?

No. John shook his head. He knew Sherlock cared about him, in his own particular Holmes-ian way. That meant Sherlock would attempt to manipulate him so that John ended up with the harmless pill.

"Time's a-wasting, Doctor," he heard the younger man drawl, breaking his concentration.

"Sherlock, shut up! I can see the clock just fine, let me think in peace!" John snapped.

Four minutes... Right, if I was a genius consulting detective trying to play stupid and take poison, what would I do? Where would I keep the poison? In front of me or away from me? Maybe I should just think of what I would do and do the opposite... Yeah that might work. But what would I do?

John reached forward and touched the bottle in front of him, his eyes on Sherlock.

No reaction.

He then leant forward and touched the bottle in front of Sherlock, keeping his eyes on his friend.

Sherlock grinned, "Really, John? Are you honestly attempting to read my body language to gauge which bottle is which?"

"No..., " John replied, hardly surprised at having been caught out. Sitting back, he ran his hands through his hair. As he did so, Sherlock stood up and sauntered towards the camera.

Oh how I wish I could wake up right now in bed, and this be nothing but a bad dream...

A quick glance at the clock set his heart racing. Two minutes. In less than 120 seconds, unless by some divine intervention in the form of Mycroft's minions, either he or Sherlock would have to take a pill and either die, or watch the other die. His heart ached at the thought of losing the man in front of him who was at the moment, peering directly into the lens and John had a mental image of their kidnapper seeing nothing but an extremely close-up view of Sherlock's forehead, eyes and nose. He stifled a laugh at the thought and then promptly blamed his nerves for such improper behaviour.

An idea manifested in his head, and without dwelling on it for long, he used Sherlock's distraction to reach forward and switch the pill bottles.

"I would actually prefer a bomb vest on me at the moment to this," John said to cover up any sound of his movement, surprising a laugh out of Sherlock.

"I'm sure," Sherlock agreed, before sobering up and returning to his chair, sitting down once more. "Don't waste time, John, choose a pill."

"Right," John said and put a finger on top of the bottle closest to him. "So this is it, then?"

"Seems so, yes," Sherlock said, nodding solemnly.

"And the fact that one of us is about to die, that's not bothering you at all?" John ventured. Ever the soldier, his hands did not shake as he unscrewed the top. Before him, Sherlock replicated his movements.

"Should it? Every single person is, at any given time, a moment away from death. How is this any different?"

John shook the pill onto his hand. It was simple and harmless looking, like most dangerous things tend to be. The clock read 11:59. They were really pushing it. Or rather, he was.

He smirked. He raised the pill in a mock toast. "Cheers."

They simultaneously placed their pills in their mouth.

The cavalry did not burst through the door in a daring, last-minute rescue.

They both swallowed.

A few minutes passed.

"Do you want to know which pill was which?" Sherlock offered, finally. "Before the symptoms begin to show?"

"Yes."

"The poison was in the bottle in front of me"

John bowed his head, two opposite emotions warring inside of him at Sherlock's confirmation: joy that his friend's life would be spared; despair that this was the end of the road for him.

"-after you switched the bottles around when my back was turned," Sherlock finished.

John's head shot up, anguish now occupying every part of his being. There was no way Sherlock could have known unless...

He'd played right into Sherlock's hand. He'd deliberately given John the opening.

That bastard.

Sherlock smiled, the one usually reserved for when he felt particularly pleased with himself and his deductions.

"Reliable until the end, John."

His body moving without his mind having a say-so, John grabbed the clock from the table and threw it with all his force against one of the walls, the cheap appliance shattering into pieces upon impact.

"Damn you, Sherlock!" John yelled, his anger and worry getting the best of him.

Sherlock reacted, firing back. "What, you would prefer I deliberately poison you? In essence commit murder?"

John did not back down, fear fuelling his anger. "No, but you could have bloody well told me which was the poison so I wasn't forced to choose!"

"And help you commit suicide instead?" Sherlock replied, disgust in his voice. "You may be willing to sacrifice yourself for Queen and country, Doctor, but I will not let you die in my place."

The sudden cough that emanated from the younger man spurred John into focusing on the present – getting Sherlock out of this room, alive.

"I'll sort you out on your stupidity later, help me figure a way out," John demanded, moving towards the door again to see if there was anything he'd missed.

"You're wasting your time doctor, the only way to leave is if someone from outside opens the door – and before you start yelling, the walls are soundproof, no-one is going to hear us... except him." Sherlock stood up, pausing for a second as a wave of dizziness caught him, before walking towards the camera.

"We've done as you requested, it's your turn to honour your end of the deal," Sherlock spoke directly to the camera. "I will die soon but I'll be damned if I let you watch." Reaching up, he ripped the device from its brackets and threw it on the floor.

John turned his head in time to see his flatmate stagger as he tried to go back to the table.

"Christ," he muttered, his anger draining out of him. He rushed to Sherlock's side and with gentle hands, helped him sit down on the floor, his long legs stretched out in front of him.

"I'm perfectly capable," Sherlock protested.

"Of course you are," John agreed, even as he crouched down and took a hold of Sherlock's wrist to measure his pulse. He bowed his head, struggling to contain his emotions –a lifetime must have passed since he'd woken up this morning, and another since he'd woken up in this room. He couldn't even tell with reasonable certainty how many minutes had passed since Sherlock had ingested the poison.

"About 5 minutes," the baritone voice interrupted his thoughts.

John lifted his head. "I hate it when you do that, you know," he remarked without any heat.

Sherlock simply smiled. "I know."

"Tell me what to do, Sherlock," John said quietly. "I don't know what to do."

Sherlock turned his head to look his flatmate directly in the eyes. He swallowed with difficulty before speaking:

"There's nothing to be done, John. Just sit down next to me."

John blinked rapidly, fighting against the sudden burn in his eyes and the lump in his throat. He sat facing Sherlock, looping his arms around his knees.

"Tell Lestrade to look into recently discharged soldiers who've been patients of your therapist..." Sherlock took a deep, shuddering breath before continuing, his face growing paler as more time passed.

John nodded, pushing down the feeling of disgust. A fellow soldier - he could hardly believe it but experience had taught him that Sherlock was hardly ever wrong. "How does my therapist come into this?"

Sherlock huffed. "She told him to look up your blog, as an inspiration to how well you'd done following your injury and PTSD. He was a big fan of yours, and of my website. Couldn't wait to prove himself to-."

Sherlock's sentence was bit off by a deep groan which had him bending forward, his forehead coming into contact with John's shoulder who immediately put a supportive arm around his friend, using the other hand to press against Sherlock's pulse point in his neck, not liking what he felt. Not only was his pulse getting weaker, but Sherlock's skin was becoming cold and damp.

"They'll come for you," Sherlock said, pushing himself away from John to lean against the wall again. "He will want people to know what he's done, to boast."

John didn't acknowledge Sherlock's attempt to reassure him, not trusting himself to speak. Instead, he watched his friend's hands begin to tremble where they lay, but couldn't be certain if the detective was aware of it.

"How are you feeling?" John asked, feeling stupid even as the words came out.

Sherlock had the audacity to smile. "Like I've been poisoned, Doctor. All in all, quite a boring way to die."

John shook his head at this. Trust Sherlock to label even his cause of death as boring.

"Although to be fair-," Sherlock paused to take a deep breath, his eyes closing for a moment, pain crossing his features before he pushed it away. "It's better than dying of a drug overdose, which while more fun, would mean Mycroft and Lestrade would never forgive me. Mycroft would probably find a way to annoy me in my grave."

"Stop it," John snapped, unable to control himself. "Just... stop."

Stop dying, he wanted to say. Instead:

"Stop... being so calm about this. You're allowed to be afraid, to freak out, to be... not-calm." God knows, he hadn't been when he'd been shot and lain bleeding in a desert, thousands of miles away from home. How was that much different from having been forced to take poison in a strange room God-knows-where with only your stupid flatmate sitting next to you, twiddling his thumbs in uselessness?

Sherlock just looked at him for a moment, before replying in a tone that in a normal person would be labelled kind. "My reaction is not going to change the inevitable, John."

For a few moments, the only thing that could be heard was the two men's' breathing. No sounds penetrated from outside.

"Oh," suddenly Sherlock whispered. "Wolfsbane."

"What?"

"Wolfsbane. Monkshood. The Queen of Poisons, John," Sherlock replied. "The poison in the pill – it's aconite. My symptoms so far fit, although I could be wrong the further it progresses."

"So all we need now is for Mycroft to burst through that door with atropine, and you'll be back to normal before dinner," John said, thinking back to what he'd learned at Bart's about aconitine poisoning – there were drugs that could reverse the effects. But no such drugs at hand.

Sherlock closed his eyes. "You have far more faith in my brother's abilities than I do, Doctor."

When Sherlock's eyes did not open, John reached out and tapped his friend on the cheek. "Sherlock. Wake up."

Sherlock came to with a jerk. "What?"

"You were drifting off," John rebuked.

"Wasn't." Sherlock reached out and started poking his legs. "I can't feel my legs at all anymore."

"Stop that," John scolded, grabbing Sherlock by the wrist. He didn't let go, however, only pressed his fingers deeper into the pulse point. Shifting positions, he too sat so he could lean against the wall, his shoulder pressing into Sherlock's.

John was no stranger to seeing friends, colleagues, brothers-in-arms, die before him; deaths from bullet wounds, shrapnel, explosives – he'd seen it all. However, even in the worst cases, there was something to be done, as long as the person had a pulse. He had his kit, he had his knowledge, and he had the nerve to try and yank every single wounded soldier back from the brink of death as much as possible.

But now, in a city far away from the desert of war-torn Afghanistan, he felt a helplessness the likes of which he'd never felt before. He barely knew Sherlock, had hardly even scratched the surface of a man unlike any he'd ever come across before. Such as, what the hell had he been doing in Florida where he helped out Mrs Hudson? How long had he been a junkie and what made him give it up? And most of all, what was the deal with the damn skull?

Under his fingers, he could feel Sherlock's pulse become sluggish as the paralytic nature of the poison took effect, slowing down his friend's heart and lungs before it would eventually cause him to go into respiratory failure. From what he could tell, breathing was already becoming a toll for Sherlock whose chest heaved with the extra effort needed to draw in sufficient oxygen.

Sherlock broke the silence with a whispered confession.

"I hated Lestrade at first... for helping me get clean. Never thanked him for it."

John nodded as he analysed this new piece of information, recognizing it for what it was. "I'll make sure he knows."

"And Mycroft. He always thought he could play God in my life." Sherlock snorted at this, resulting in a coughing fit. "He'll hate himself for not stopping this." Sherlock paused for a moment. "Don't let him."

John squeezed Sherlock's wrist as a sign of acknowledgement. He wondered if he should say something, a goodbye of some sorts...

But, God help him, there were no words...

A minute passed and John dared a glance at his friend. Sherlock had grown extremely pale and with his eyes closed, the only colour on his face seemed to be the alarming blue of his lips.

"Sherlock." John shook his wrist, feeling a tiny burst of relief when Sherlock slowly opened his eyes again.

"John," Sherlock whispered, each breath now a task. "It's been an honour."

"Sherlock," John choked out against the painful lump in his throat. "Don't." John didn't elaborate, unsure himself of what he meant. Don't what? Don't die?

"Too late," Sherlock replied and John didn't need to look to see the slight smirk that graced the man's features.

John didn't need to hear his friend take a shuddering last inhale to know that Sherlock didn't breathe again.

John didn't need to feel to know that what slight tension there had been in Sherlock's wrist disappeared along with the last beat of his pulse against his fingertips, his friend's head slumping to rest on John's shoulder.

He couldn't see anything beyond the tears blurring his version.

He couldn't hear anything beyond the screaming in his mind.

If he did, he would have heard the door to their prison burst open. He would have seen officers in black swarm the room.

He didn't see Lestrade crouch in front of him, grief paining his features.

He didn't see paramedics take Sherlock away from him.

If he had truly observed, as Sherlock always wanted him to, he would seen his friend brought back to life.

Khatum