Author's Note: This story was written for a friend of mine who got me into writing for the fandom. That being said, he you happen to see this posted anywhere besides here or on my AO3 account, please report it and then message me! Thank you!

The First Time:

It did not take most of Sherlock's powerful deducting skills to know that John was beyond worn out. For the last 48 hours, the two of them had been running from one side of town to the other in an attempt to catch a serial killer targeting prostitutes. It had ended just over an hour ago with a successful arrest. Although Lestrade offered them a ride back, Sherlock had turned him down, knowing a taxi would be faster. Unfortunately, they were unable to catch a cab. When Sherlock complained, John pointed out that they were in a shady side of town. Cabbies normally did not have to deliver to this area, and not too many people in this part of town wanted to be picked up. So it was only natural that they could find any taxis. After five minutes, Sherlock conceded defeat and suggested they take the Tube.

Now John was sitting next to him. Sherlock glanced over and could not keep himself from observing: bloodshot eyes, dark circles, periorbital puffiness, and nystagmus. John's eyes kept closing for a moment before he jerked slightly and shook his head. Three times, he unsuccessfully tried to stifle a yawn. His eyes were focused on nothing, and his blinking was slower than normal. Yes, John was most definitely suffering from sleep deprivation. It fascinated Sherlock to see just how much John depended on sleeping. He was practically passing out next to him.

"Long case," John commented, rubbing his eyes and blinking several times.

Sherlock quickly looked away and responded, "Indeed."

"How long until our stop?" he tried to ask nonchalantly.

Smirking, Sherlock glanced at the map that marked the different stops. They had just left North Harrow. He quickly scanned down the track as he calculated the time. "About a half an hour," he finally answered.

John groaned and cupped his face in his hands. "God, why can't serial killers just take a vacation for a week?" he asked.

"What would we do for that week?" Sherlock asked, genuinely horrified. He could not imagine anything more boring than London being peaceful for any amount of time.

John laughed as he heard this, and Sherlock registered that it was a bit bitter. "Well, you would probably shoot out at least one of our walls, fill our flat with piles of dead body parts, perform several experiments that would either threaten to destroy our flat or drive me insane, and yell at the people on the telly. I, on the other hand, would sleep the entire week through."

"Impossible," Sherlock responded, scoffing a bit.

John forced a smile to his face and looked up at Sherlock. "You've never served in the army," he commented before leaning back. He closed his eyes for a moment. "Or you would realise just how possible it is."

Sherlock did not comment. Instead, he pulled out his cell phone and began researching for any news about crimes in London. His mind was still too wired from the adrenaline high for him to relax just yet. All he wanted to do was move onto the next case – solve the next mystery. As he scanned down the different reports, Sherlock felt something warm and firm fall into him. He looked over to find John leaning against him. Observing John carefully, Sherlock could hear his steady, slow, and even breathing. Definitely sleeping. Sherlock's eyes softened as he examined John. He looked like a completely different person while sleeping – as if he had just lost ten years. The hard lines on his face had melted away, almost unnoticeable in the pale lighting. There was no military-instilled tension in his body or the slightly haunted expression that could be seen on his face more often than Sherlock liked; he was completely relaxed, completely open. A warmth blossomed in Sherlock's chest, and he frowned as he felt it. It made him feel… good… content… but he could not name what it was. Suddenly, John shifted a bit, muttering something under his breath. Sherlock resisted the temptation to wrap an arm around the sleeping former army doctor. Looking back up, Sherlock smiled softly. He was finally beginning to understand the appeal of sleeping.

The Second Time:

"And how does that make you feel?" John inquired jokingly as he walked into the living room.

Confused, Sherlock looked at him from where he was laying on the sofa. "What?" he asked. John always managed to mystify him with those random questions.

"Never mind," John muttered, shaking his head.

This only made Sherlock more curious. When it was clearly something John thought he should know, Sherlock always made a point of remembering it. Even now, he remembered that the sun was the centre of the solar system, although he still was not sure why it was so important for him to remember. Taking a moment, Sherlock tried to deduce why John thought he should understand the reference. It was a phrase, so not something scientifically or medically significant. Since it was not something Sherlock heard in even random conversations, the phrase could not be linguistically significant. So that meant it was – "Pop culture reference?"

"Yes," John answered after looking over at Sherlock in surprise. "The stereotypical sentence for a psychiatrist to ask the patient when the patient is laying on the sofa."

Quickly, Sherlock filed that information away. He deemed it useless, of course, but if it was important to John then he would remember it. Sitting up, Sherlock felt curiosity gnawing at him. "Did your psychiatrist ever ask you that?" he asked before rising to his feet.

John shifted uncomfortably, telling Sherlock that he was treading into something John would prefer to leave uncharted. "Of course she did," he replied, sitting down on the sofa Sherlock had just left. "She wanted to know what I felt and thought about everything. Although I did not lay down in the traditional fashion."

"Oh?" Sherlock inquired, raising an eyebrow. "How were you supposed to lay?"

John twisted around on the couch and laid down. Very carefully, John folded his arms and closed his eyes. He shifted a bit in order to get comfortable. "This is the traditional position to lay in. And then the psychiatrist sits in a chair and faces the patient. As the patient talks about his life and feelings, the psychiatrist writes down notes."

Finding this all very entertaining, Sherlock grabbed the chair and turned it away from the telly. Once it was facing John, who had looked up in alarm, Sherlock grabbed a pen and paper and sat down. "And what is it like living with the most brilliant man in the world?" Sherlock inquired jestingly.

John laughed before relaxing back into the sofa. "It's practically a full-time job. I live with a genius who acts like a three-year-old. His brilliant deductions are followed with socially ignorant comments. Our refrigerator is constantly filled with body parts, and his experiments normally clutter the house." Sherlock scowled as he heard this. "However," John finally added, "I have never had so much fun in my entire life. Every day, I wake up and don't know what is going to happen before the sun sets."

Eyes sparkling from the praise, Sherlock tried to keep himself from smiling only to fail. John had that effect on him. No one had been so open with him nor had encouraged him to such an extent before. Every time John sang him praises, Sherlock could not help but soak them up. It was something he had been deprived of for most of his life, and it was something he never wanted to live without again.

"It's your turn," John said, his eyes still closed.

Sherlock was confused by the sudden statement. "What do you mean?"

"I played the patient, so you have to play the psychiatrist," John answered. "What do you make of me? Am I still a PTSD victim with trust issues, an intermittent tremor, and a psychosomatic limp?"

Pausing a second, Sherlock gazed at John intently. He had yet to open his eyes. "No," Sherlock murmured, leaning forward as he observed John. "Your limp was psychosomatic, and you no longer suffer from it. You do not have an intermittent tremor anymore either. Your PTSD has improved immensely over the last couple of months. You do not trust easily, yes, but that does not mean that you are incapable of trusting anyone," he pointed out. "So I have come to the conclusion that your previous psychiatrist was completely incompetent, and you should never see her again. What do you think of that?"

John did not answer. Quickly, Sherlock checked his breathing pattern and posture and deduced that he had fallen asleep. He watched John sleep for a moment, awed once more by how peaceful John looked. Finally, Sherlock rose to his feet. "I can't believe you fell asleep on me," he murmured to John before heading into the kitchen in order to study his bacteria cultures. It was something that was guaranteed to not wake John.

The Third Time:

Every now and again, John would push himself too far. After all, he was not as young as Sherlock – and even if he was, he still would not be able to keep up. Sherlock was a "freak" after all. He did not need as much food or sleep as the average person. And because he had always lived like that, he sometimes forgot that John was normal. So when John collapsed on the sofa next to him, Sherlock was surprised to see just how worn out he was after a long day of literally running around London. Rubbing his face, John shook his head.

"If you ever retired, I would not miss this," he stated matter-of-factly.

Sherlock chuckled as he heard this. Retirement? Him? Never. How boring would it be to retire? What would he do with his life after that? He might as well do something as mundane as beekeeping if he were ever going to retire. "I somehow doubt that," he replied.

"Seriously, Sherlock," John said. "We cannot keep pulling all-nighters like this. It's not good for our health, and neither of us are getting any younger."

Sherlock answered, "You're only half correct with that deduction."

"How so?" John asked, not following.

Looking over at his flatmate, Sherlock responded, "You cannot keep pulling all-nighters like this. I, on the other hand, am completely capable of doing so."

John scowled at him. "I don't like letting you run around London alone. Last time I let you do so, you almost died before I could get there. Or have you forgotten that?" he pressed, his tone sharp.

Eyes widening, Sherlock felt surprised as he realised John's motivation to try to keep up. He was trying to keep Sherlock safe. Trying to make sure Sherlock did not wind up in another situation like "A Study in Pink." Sherlock felt that warm feeling spread through his chest again, and he quickly picked up his violin. Sherlock started to play Nocturne Op. 9 No. 2 by Chopin, knowing John would not notice that it should have a complimentary piano piece. Although John had never told Sherlock himself, his flatmate sincerely enjoyed listening to him play the violin. Sherlock looked over at John to find him fighting to stay awake. Sherlock then returned his attention to playing. When he felt a soft thump against his back, he smiled smugly. His plan had worked out perfectly. As John slept against him, Sherlock continued playing until the piece was finished. Then he started playing another one just so he had the excuse to stay right where he was – right where John kept him.

The Fourth Time:

"Have I ever told you what a fantastic flatmate you are?" Sherlock inquired as he set a fresh cup of coffee in front of the former army doctor.

Raising an eyebrow, John asked, "What do you want?"

"I need you to do me a favour," Sherlock said. He knew that John did not enjoy participating in his experiments, so he needed John as agreeable as possible. "You can, of course, say no. There's only a man's life riding on this experiment, after all. So do not think I'm forcing-"

John cut him off, "What do you want me to do?"

"Well, I need to study the effects of a tranquiliser on you," he said. John opened his mouth to object, obvious by how his brow had furrowed together after hearing Sherlock's proposition, but Sherlock managed to cut him off. "Let me remind you that a man's life is on the line, John!" He knew the only way to get John to help him would be to play on his humanity.

John frowned deeply, a moral dilemma emerging in his mind. "What exactly would this experiment entail?" he pressed.

"Well, our client testifies that he was tranquilised by the hired assassin and could not defend his sister before he blacked out," Sherlock explained, slightly emphasizing the "our" in that sentence. If he could make John subconsciously more inclined to help, he could guarantee John's help. "I identified the type of tranquiliser used on him. I need to study the speed and effects of it."

Shifting a bit, John set his jaw, and Sherlock bit back a smile. If John was moving, it meant that he was still thinking about it. He was on the fence. "And why do I have to be tranquilised? Why can't you be? Wouldn't experiencing it help you more?" he queried.

"Because you have a closer build and structure to our client than I do. And both you and our client are ex-army. I need to see how you would fight after being tranquilised and how quickly the tranquiliser affects you," Sherlock explained carefully.

John licked his lips and cleared his throat. "And this would definitely help out our client?" he pressed, soundly uncertain.

"Undoubtedly," Sherlock confirmed before giving John his excited look. It always made it harder for John to say, "No," when Sherlock visibly showed how eager he was.

After a moment of silence, John continued, "And you want me to fight you?"

"That's correct," Sherlock said.

John smiled as he heard this, and Sherlock knew John was about to accept. "Alright."

"You're amazing, John!" Sherlock exclaimed in delight as he rushed back into the kitchen to get the syringe. "Remember, you have to fight me as soon as I remove the needle."

John answered, "Trust me, I am not about to forget that."

Sherlock emerged from the kitchen with the syringe in his hand. Rolling up his left sleeve, John offered his arm to Sherlock. Swiftly, Sherlock tranquilised him before tossing the syringe back into the kitchen. As soon as the syringe fell into the sink, John took his first swing at Sherlock. A strong burst of pain seared across his cheek as he took the blow. Quickly, Sherlock dodged the next blow and noticed that John was already losing his equilibrium. John staggered to one side, stumbling over his own feet as he tried to face Sherlock again. It struck Sherlock as interesting that the tranquiliser had started taking effect in the matter of seconds. As John swung at him again, he fell over. Sherlock instinctively caught him, stumbling back a bit as he tried to counterbalance John's weight. Fighting to stay awake, John struggled for a moment longer before passing out on top of him. Sherlock glanced back at the clock. It had taken less than two minutes for John to be unconscious. He pulled John closer to him and slowly drug him over to the sofa. Dropping John onto it, Sherlock noted the time again before shifting him into a more comfortable position. Now all he had to do was see how long it would take for John to wake up. If it wasn't for another hour, their client was innocent of all charges. Sherlock looked back down at John, who was sleeping like a baby, and felt that warmth spread through his chest again. Smiling to himself, he could not help but think that he would not mind it if John participated in more of his experiments.

The Fifth Time:

Sherlock had completely lost himself in researching the chemical properties in a sample of Chinese food. His current client explained that he and his wife had been trying to be a bit "fresh" in bed and added bondage. According to the Yard, the wife was choked to death by the lasso wrapped around her neck. However, the husband insisted that the lasso was loose and had not been causing any loss of air. After noticing the lack of bruising around the wife's neck, Sherlock had decided that the husband was innocent, which meant something else must have caused her death. He was currently testing all the food in their house, hoping to find a poison laced into her food. Since she would have cooked everything else, the Chinese food was his best bet on cracking the case.

He had lost track of time, and it was only when he heard a strangled cry that Sherlock came to his senses. Looking out the door, Sherlock could see John turning sharply in his sleep as he came close to falling off the bench he was laying on. Sherlock jumped to his feet and rushed over to John. He grabbed John by the shoulders and gently shook him. "Wake up, John. It's just a dream," he said. Eyes opening, John fought against Sherlock for a moment. Sherlock could see from the look in John's eyes that he still was hallucinating. "John, calm down. You're in St. Bart's with your flatmate," he calmly stated.

John's eyes slid back into focus. Blinking a couple times, John stared at Sherlock before realisation washed over him. "Sherlock?" he called out, uncertainty colouring his voice.

"Yes, John, it's me," Sherlock responded, smiling a bit in hopes that it would provide the former army doctor some comfort.

Pressing his lips together, John looked disgusted in himself. "Sorry about that," he muttered.

"It's alright," Sherlock answered. When John avoided his gaze, Sherlock dipped down in order to force eye contact. "Remember what you told me the first night we were flatmates? It's all fine. This is normal for former soldiers, and you have no reason to be ashamed."

John let out a long, shuddering breath and slowly nodded. After giving him a closer look, Sherlock noticed there was a wetness in John's eyes. So not only was he dreaming about Afghanistan, but he had been dreaming about losing one of his close friends. Sherlock frowned, glancing back into the laboratory. The computer was running the components of the test samples already; it would alert Sherlock when it found something. Glancing back at John, Sherlock could tell that his flatmate needed to go back to sleep. For the umpteenth time, he was grateful that he did not depend on sleep as the common rabble did. He sat down next to John. Previous experiences with him told Sherlock that his presence was soothing to John.

"You should go back to sleep," Sherlock said, leaning back into the uncomfortable bench.

John scoffed. "I would, except you're sitting where my head goes."

"I don't see why that should stop you," Sherlock remarked indifferently.

Jaw dropped, John stared at Sherlock for a long moment. Sherlock could practically see the thoughts running through John's head as he tried to understand everything that had just happened. After a long moment, John lied back down and rested his head on Sherlock's lap. Sherlock resisted the temptation to run his fingers through John's hair. Instead, he took to drumming his fingers on the side of the bench. It did not take long before Sherlock felt John's breathing slow down. He looked down and felt that distinctive warmth crawl through his chest again. Very slowly and carefully, Sherlock petted John's head. John stirred a moment, making Sherlock freeze, before resettling and sleeping once more. Smiling to himself, Sherlock ran his fingers through John's hair again. It felt so light and soft in his fingers; it was much softer than Sherlock's dark curls. A sense of peace settled over Sherlock as he sat vigil over John's slumber. It was so peaceful that Sherlock ignored the computer when it alerted him to finding the toxin. After all, the client could wait until morning.

The Roles Are Reversed:

Sherlock felt ill; it felt as if a block of ice had painfully lodged itself in his stomach. Their night had not gone as planned at all. After hearing a prisoner had escaped, Sherlock and John had headed out to help Lestrade wrangle him in. The night ended with guns being fired. In the confusion, John tackled Sherlock to the ground and was grazed by a bullet. Had John been two seconds later, Sherlock would have been shot. What's worse, if John had been a second later, he would have gotten shot. And this led back to Sherlock's ill feeling: John had come a second away from dying, and it was entirely Sherlock's fault. John was limping slightly, which frustrated Sherlock even more. Tonight was going to send John back in his progress of getting over his PTSD.

"I'm going to head up to bed," John declared as he went to head up the stairs to his bedroom.

Instinctively, Sherlock called out, "No, wait!" John stopped in his tracks and turned back to look. Sherlock could see the haunted look in John's eyes; the memories buried carefully were fighting to emerge. "I'm so sorry, John," Sherlock murmured sincerely.

"What happened tonight was not your fault," John responded. "But I'm tired and I need to go to sleep."

Before Sherlock even thought everything out, he blurted, "No." John looked at him in surprise, and Sherlock immediately rebuked himself for acting so impulsively. What was he doing, acting on sentiment like that? But he honestly didn't want John to sleep alone that night. He knew what such a night would have in store for John if he slept alone.

"Sherlock?" John inquired, forcing Sherlock to come back to the present. "Are you alright?"

Quickly, Sherlock recovered, "Yeah. It's just the shock talking."

"You don't go into shock," John pointed out. Sherlock avoided his gaze and started pointedly at the bedroom. After a minute of silence passed between them, John said, "Get ready for bed. I'll be in in a few."

Relaxing, Sherlock was grateful that John managed to take the hint. He quickly brushed his teeth and then hopped into the bed, waiting anxiously for John to join him. Listening carefully, he could hear John hobble down the stairs. He limped into the bedroom and quickly settled onto the bed. Once John was comfortable, Sherlock turned off the lamp and sent the entire room into darkness. He could hear John breathing next to him; his breathing was uneven. John shifted several times, trying to get comfortable but unable to.

Finally, he said, "I just don't think this is going to work out. I'm going to head up to my own bed."

"No," Sherlock barked, rolling over and wrapping his arms around John's waist to keep him trapped. "Just trust me. Stay here."

John hesitantly placed a hand on Sherlock's arm. "Alright, Sherlock, I'll stay," he stated, patting Sherlock's arm.

Sherlock tightened his grip slightly and rested his head on John's abdomen. John's heartbeat was as soothing as it was strong. Instinctively, Sherlock tried to draw John closer. John was here – safe and sound. Gently wrapping his arms around Sherlock, John relaxed and finally became comfortable. Sherlock had been planning to wait until John was asleep before going to sleep himself, but the mixture of John's scent, the steady beating of his heart, and the warmth that surrounded him lulled him into a sleep far faster than he anticipated. The last thing he remembered was John asking him if he was still awake; Sherlock had been too exhausted to reply.