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Sherlock wasn't supposed to have a heart. He had been told time and time again what he was: heartless, cold, unfeeling. Sociopath. That definition was enough to become him, something to excuse his apparent lack of heart.
Except that he had one now. Or perhaps it had always been there, and he had just been unable to feel its beating until Moriarty forced him to listen. Now Sherlock couldn't stop hearing it, and he wished to God he could forget it was there. The thing beat in his chest, full and heavy, exhausting to carry around. He hated it.
I will burn you.
Every night the words were whispered softly into his ear as his mind looped that moment at the pool again and again. Though the space beside his bed was empty and cold, Sherlock could almost feel warm puffs of air against his neck where he was speaking the words that made his hair stand on end. Some nights he rolled over just to make sure Moriarty wasn't there and was rewarded with nothing but the silent floorboards.
He hadn't seen Moriarty in weeks, but every night he haunted Sherlock's dreams, lingering there and poisoning his subconscious, and Sherlock couldn't get him out.
He dreamt of fire.
Sherlock remembered when John had nightmares about the war. The man would wake up in a cold sweat, shivering and gasping for air. Sherlock had walked in on him once, after he'd woken up from one of those PTSD dreams. He had been curious, but hadn't been prepared for the way his stomach filled with ice upon sight of the doctor trembling in his bed. After that he had made the decision not to disturb John after a nightmare again, for both John's sake and his own.
Sherlock's dreams were worse than that. Because even though John would wake up in the middle of the night with those memories of war and cold desert nights branded into his skin, Sherlock woke up with heat against his flesh and fire searing his thoughts. Sherlock would breathe deeply through his nose in deep meditation in an attempt to feel like he was on solid ground again.
Sometimes he screamed. He screamed at Moriarty, he cried out in pain, but most of all he cursed at himself for ever allowing this to happen, even in a dream. Why couldn't he stop it?
It was a horrid kind of yell, involuntary and animal sounding, and yet unmistakably human. Sherlock woke up some days and his voice felt hoarse, and talking was painful shame. It didn't take a consulting detective to figure out how it got like that. Even John knew, but he returned Sherlock's courtesy of not prying into his nightmares by not disturbing Sherlock's own.
Sometimes, though very rarely, he wished that John would ask about them. Except that he had no idea what he would have said in response, because the truth was frightening and definitely not good.
He dreamt of a world aflame, of a heart being set on fire, and of John being burnt in effigy as Sherlock watched. Sherlock could feel the dull organ beating uselessly in his chest, could feel the heat pressing against his spine, as he watched John burn to ash.
Some say the world will end in fire. And Sherlock's did, every single night.
John was always in so much pain in the dreams, and Sherlock could feel it, through John's shouts for help and his animal cries. More often, however, John was silent, only staring silently at Sherlock as he stood against his stake. He looked pained. Pained for Sherlock, even though John was the one being consumed by flames. It was at that time in the dream that Sherlock felt heat rise in his chest, an ache that came from his torn, riddled heart. John and Sherlock both burned.
Once in awhile John wouldn't be burning. He would be perfectly fine, laughing alongside Sherlock as if he hadn't been set on fire last night, or burnt alive the night before.
Then Sherlock glanced away and when he looked back at John, he wasn't laughing or happy. John looked tired, and it was the same pained look that he wore when the flames licked his legs. John's hand brushed up against Sherlock's, his lips pressed against his neck, and Sherlock felt his supposed heart wrench.
John leaned his head against Sherlock's shoulder in exhaustion, in undeniable fatigue, and whispered softly, "Why are you doing this to yourself?"
Sherlock looked at him and could already feel the heat beginning to consume them, but had no control over it, over any of it. John looked at Sherlock, so pained, and Sherlock hurt. If only he could stop it this time, stop the fire from spreading…
"You know why," Sherlock said simply, and John nodded, and then they were both engulfed in flame.
It was said to be impossible to feel pain in dreams, which made sense, because Sherlock never did. Not physical pain anyway. But there were so many other kinds of pain.
Sherlock's thoughts were always wrapped in a kind of intensity, but this was the sort of single minded obsession that felt painful. It twisted his insides and jumbled his thoughts, and it hurt, because he never got any closer to a solution. He was trapped in a limbo of burning, only to rise from the ashes when he burst into consciousness, hands shaking.
It wasn't physical pain, but it might as well have been, as Sherlock watched his heart be burnt out of his chest, as he watched the smoldering ashes of London fall around him, as Moriarty laughed, and as flames drowned John once again. Every night was the same.
Sherlock was not yet asleep, but he could already feel the phantom memory of the dream curl around his mind in anticipation, suffocating it, choking off any kind of real rest to be had. He closed his eyes, knowing that not even he could evade sleep forever, that he could only prolong the inevitable. As he slipped into another nightmare, he could already feel his heart crumble to ash in his chest.
As he watched his world burn, Sherlock Holmes screamed.