A/N So this has a touch of Supernatural in it. Demonic possession and Sam and Dean and whatnot. In this story, Mary doesn't exist and John and Sherlock have been dating for about a week. Sherlock slipped into a coma after ODing when he got on the plane after killing Magnussen. TRIGGER WARNING!!!! References to attempted suicide and severe panic attacks. Let me know what you all think. I may continue this one, just not sure yet. 

Suggested by MandyFullertonLee

Enjoy<3 

 "Sherlock, what the hell is going on?" I ducked as my friend fired another shot at me. Why was he doing this? Fear clutched my heart as more shots rang out. We had been investigating a murder and found ourselves in a near-empty garage. We got separated somewhere along the way, and then Sherlock appeared out of nowhere, gun in hand and rage on his face. I was trying desperately to not panic, memories of battle flashing before my eyes.

"John?" His voice echoed along the walls, sounding taunting and cruel. "O where are you little Doctor? Don't be shy, step into the light." I bit my fist to keep squeaks of terror from falling from my lips. "He is crying you know? The brilliant detective is trying to break free, trying to save his little pet. It's so, human." His words were confusing, but I was too scared to think on them. I found a small room and hid, praying that whatever was going on with my friend had slowed his senses enough that he wouldn't see the room. He continued talking, his words sending chills along my spine. He talked of how he hated me, how he was going to relish the thought of killing me.

The sounds stopped, silence filling the garage. I started to hope that he had given up when the door slammed open and Sherlock grabbed me by the hair, violently pulling me out of the closet. I cried out from pain and fear as he threw me to the ground. Pain flowered in my side as I connected with the hard concrete. I tried to crawl away, but was stopped when I felt his foot press down on my ankle. I cried out once more as I felt the joint cracking under his weight. He laughed; a deep, unholy sound at my pain. He drew his foot back and walked around to stand beside me. I tried once again to crawl away, dragging my now injured ankle along behind me. I felt the toe of his shoe violently dig into my side as he kicked me. I stopped my squirming and rolled onto my back, staring up at the man grinning down at me.

"Sherlock, please, don't do this." I fought through the pain as I spoke, trying to find Sherlock within the stranger claiming to be him. He laughed again and dropped to his knees, gripping my throat in his hands and leaning down so he was inches from my face.

"He can't hear you. But believe me he can see you." His grip tightened and I struggled against him, clawing at his hands. "His poor little doctor, having the life squeezed out of him by the only person he ever really trusted." My vision started to fade around the edges and I could feel my throat being crushed by the sheer force he was applying. My strength started fading. Just as unconsciousness was about to take me, I heard shouting. The man above me froze, his eyes suddenly turning solid black as he looked up. He let out an inhuman growl and sprung away from me. The pressure left my throat and I started coughing as the air hit my deprived lungs. My ribs stung from the blow they had received earlier and my head was spinning. I rolled onto my side and propped myself up on my elbow, trying to get my heart working again. I saw Sherlock fighting two men; they were dressed in ratty plaid shirts and ripped jeans. One of the men had a blade in his hands and was trying to kill Sherlock. I fought to stand, still coughing. Before I managed to get to my feet, the taller man had pinned Sherlock's arms behind his back and shouted at the one with the blade. He swung the blade, aiming for Sherlock's heart.

The scream that was ripped from my broken throat was painful and terrifying. Everyone froze, including Sherlock.

"Please, don't kill him! That isn't Sherlock, I know it's not. He wouldn't do this. Not to me." Every word felt like a thousand knives grating along my vocal chords. He had probably fractured my windpipe.

"Listen man, he just tried to kill you." The one with the blade was looking at me like I was stupid, and even though I knew that look very well, it made me mad.

"Dean," the man that was holding Sherlock said; his voice softer than the other's. "Grab the cuffs and book."

"Seriously Sammy, we are just going to exorcize it?"

"Just do it, Dean!" Dean grumbled and walked over to a car I hadn't noticed before. He opened the trunk and grabbed a pair of intricately carved handcuffs and an old leather book. Sherlock wasn't fighting anymore; instead he stood perfectly still, eyes trained on me.

"O the brave little soldier, trying to save his detective. Why do you love him so much Doctor Watson? He doesn't even like you. You should see all the nasty things he has in his head about you." Those words hurt and I glared at the ground, blinking away tears. I heard shuffling and looked up to see them forcing Sherlock, who was now cuffed, onto his knees. The taller one looked at me with compassion in his eyes.

"That isn't your friend talking. He is just trying to rattle you. Are you and him, together?" I nodded. We had only been dating for a week now, but I knew he cared deeply for me. "OK, then you would know how he truly feels. Now this is important, has he been severely injured since he started acting like this?" I shook my head, not wanting to speak in order to prevent any further damage to my throat. The taller one nodded and turned, grabbing the book from the one named Dean. He flipped through the pages for a few minutes before settling on a page. He started speaking in what sounded like Latin. As soon as the words started falling from his mouth, Sherlock's face contorted in in pain. He started lashing and screaming, cursing the three of us.

"What is happening?" No one answered me, focusing instead on the writhing man before us. Sherlock froze, eyes landing on me, burning holes in my soul.

"You should have let me die on that plane." His voice sounded like Sherlock's again, and his words tore through my mind. He threw his head back and screamed, black smoke spilling from his mouth. I hit my knees, pain tearing my soul in half. I watched as the thick black smoke swirled around my boyfriend's body for a moment before disappearing into a burning ring on the floor. Sherlock fell limp to the ground and I scrambled to him, praying that the worst was over, that I could have my Sherlock back. I ignored my protesting ankle as I reached him, lifting his lifeless form onto my lap and checking his vitals. His heart rate was elevated and his skin was more pale than normal, but otherwise he looked fine. I cradled his head and started sobbing in relief.

"Hey, listen we have to take off. Your friend should be fine, just give him a moment to wake up." The taller man walked over to us, clutching his arm. I noticed that he was bleeding fairly badly.

"Wait, let me check you over. That cut looks deep and you all owe us an explanation." They objected at first, but I insisted. Soon enough we were loading an unconscious Sherlock into the back seat of their car and heading to our flat. We made our way upstairs, the two men carrying Sherlock as I could barely even walk on my own. Mrs. Hudson heard the commotion and followed us upstairs, babbling about how we should take better care of ourselves. She bustled about the kitchen, undoubtedly making us tea. I motioned for the two men, whom I now knew to be Sam and Dean Winchester, to set Sherlock on the couch so I could monitor him while I worked on them. I hobbled into the bathroom and retrieved my medical kit. I had to wrap my ankle soon. I focused on Sam first; he was the one with the bloody arm. I cleaned and dressed his wound, finding comfort in the simple task. As I bandaged him up, they explained everything, telling fantastical tales of demons and other such creatures.

Sherlock had somehow gotten possessed by a demon, probably the same one that caused all of the murders that we had been working on. Dean said that they could hop from person to person; keeping the body functioning while they were inside it.

"How often does this happen?" I had never heard of anything remotely close to this in years, at least not here.

"It hasn't happened in a long time; usually the Men of Letters keep everything under wraps over here. But we are kind of the leading experts in demonic possession."

"And the people that had been possessed, they survive?" The room got quiet for a moment and I felt my stomach tighten.

"If an exorcism is performed in time and the body wasn't harmed too badly, then they can usually walk away alright." Sam spoke hesitantly, looking more uncomfortable with each word. "Though if they aren't mentally stable they can have issues with the damage it can do to the mind." My heart clenched and I glanced back to the unconscious man on the sofa. Sherlock didn't handle unknown things very well. I shook myself out of my thoughts and gave the tall man a final once over before signaling for his brother to take his place. Dean wasn't hurt nearly as bad, only a heavy duty black eye forming and a nasty split lip. I silently congratulated my boyfriend for getting such good hits in.

"So, what happens now?" I asked as they started packing up their stuff. "What do I tell Sherlock?"

"If he remembers anything, tell him it was a hallucinogenic or something."

"And if he doesn't remember?" Sam looked at Sherlock and seemed to ponder over the question.

"If you think he can handle it then tell him what happened. More importantly if you think you can handle that conversation." I nodded, taking a seat in my armchair and starting to wrap my ankle. The Winchesters left, handing me a piece of paper with their number on it as they walked out. I finished wrapping my swollen joint and moved to sit next to Sherlock, pressing a soft kiss to his forehead.

"Is Sherlock awake yet?" Mrs. Hudson came in from the kitchen carrying the tea set on the serving platter. She looked concerned when I shook my head. She set the tea on the table and patted my shoulder before leaving the flat, requesting I inform her when Sherlock woke. The flat fell silent as she left, leaving me sitting next to Sherlock, sipping tea and trying to fight the rising panic.

You should have let me die on that plane. Those words kept bouncing around my head. I bounced my knee, trying desperately to shake the harsh words from my thoughts. Sherlock had overdosed on the plane after shooting Magnussen, never intending on returning. He had killed the vile man to protect me, but Mycroft had brought the full force of the British government down on him. They tried to send him away on some lengthy mission as a punishment and he decided to not return. I later found out the mission was a suicide mission. When he landed, he was unconscious. I did my best to revive him but he slipped into a coma.

You should have let me die on that plane. Images of him lying in the hospital bed, hooked up to various machines flashed before my eyes. The feeling of his cold, lifeless fingers in mine sending chills along my arm.

"John?"

O the brave little soldier, trying to save his detective. My chest was tightening and I could see Sherlock's face hovering over me. I could feel his hands on my throat.

"John, what's wrong?" I couldn't breathe. I could feel someone gripping my shoulders.

"No, no please, no!" I couldn't tell who was talking, but they sounded terrified.

"John!" There was another voice. It was Sherlock. He was in trouble. I shook my head, trying to clear my vision. I had to save Sherlock.

The brave little soldier, I felt a hand on my cheek, you should have let me die.

"John!" My vision started to clear and I saw Sherlock, kneeling in front of me. There was fear in his eyes.

"Sher-Sherlock-" My throat was aching and his hands were squeezing my shoulders tightly. I shook my head to try and focus, catching his eyes and trying to figure out what was wrong. We were against the kitchen door, sitting on the floor, my back pressed against the cold glass. My breathing was uneven and my hands were shaking violently. I must have had a panic attack.

"John! John, are you alright?" He patted my cheek with one of his hands, pulling me farther out of unconsciousness. "John, please say something!" I started to get my breathing under control and looked up to the man kneeling before me. There were tears in his eyes and he looked terrified. He had never seen me like that before.

"Sherlock-"

"John! Thank God!" He wrapped his arms around me and held me tight, seeming to ignore the tension that filled my body. I pushed him off me gently, remembering what he had gone through. I needed to make sure he was OK. "What's wrong John? Is everything OK?"

"Yes," my throat scratched and I coughed. "I'm fine. Do you remember anything?" His eyes darkened and he backed away from me. He nodded, closing his eyes in shame.

"I- I am so sorry John."

"No, no that wasn't you. I know you would never do something like that."

"But that was me John; I could see myself beating you. I could feel my fingers crushing your throat. I could hear the words spilling from my mouth. I could hear you screaming. I was in there, but I couldn't stop it." He buried his face in his hands and I adjusted my position so I was seated right in front of him, draping my legs over his and wrapping my arms around him. My ankle screamed in protest.

"Sherlock, it was a hallucinogenic. You were drugged. Nothing you did there matters, because it wasn't you. You were locked in your own mind and you panicked." I took his face in my hands and pulled his chin up so I could see his perfect eyes. They were filled with tears. "Sherlock, I suffer from PTSD, you know this. I will freak out about stuff. Do not blame yourself for this. That amount of stress would trigger anyone." I smiled softly at him, pulling him closer to me and pressing a soft kiss against his lips. I couldn't tell him the truth. He couldn't handle it. One day I would have the Winchester brothers come back and explain everything, but not today. For now, I just wanted to be with my boyfriend. He finally calmed down enough to start responding to my kiss. Soon enough, we stood and made our way to the sofa. We curled up together and spent the rest of the day watching crap telly. Though no matter how I tried, I couldn't escape the words that still echoed in my skull

You should have let me die.