"For such an observant man, you really are quite dull about the wits,"
Sherlock's head snapped around so quickly he felt his neck crack and his brain rattle in his skull. John was standing in the doorway to their flat; hands limp at his sides, and grinning at him with a terrible and decidedly not normal expression, a splash of teeth visible through cruel lips.
"John?" Sherlock is on his feet, backing away before his brain even catches up to the situation.
"Not J-ohn," a singsong voice that has no place being in their flat.
"What are you talking about?" Sherlock is almost frightened. He doesn't know if John is having a fit, or a psychosomatic break, or why his friend is advancing so terrifyingly slowly.
"You really aren't very sharp, you know that?" John's face twists into an atrocious mockery of a delighted smile, "John hasn't been here for a long time,"
Now Sherlock is convinced his flat mate has had a mental break of some type. Ways to immobilize the smaller, but much stronger, man run through his head, but before he can decide on a course of action John has leapt across the room and pinned him to the wall. Hand crushing against his collarbone, Sherlock gasps and tries to wrench himself away, but the iron strength of that grip keeps him locked tight. He manages a gasping, strangling noise as his long fingers scrabble at the hand slowly tightening around the base of his throat.
"No, Johnny Dear has been gone for days now. Not that you've noticed. Just keep talking to him even when the body isn't in the flat," whatever it is inside John tsks at Sherlock and rattles him, like a terrier with a rat, "Was easy. So, so lost was our Dear old Johnny. So, so… lost,"
Sherlock fought, his mind refusing to understand.
"Thrown away, passed around, shunted to the side, taken for granted, ignored when he was right in front… Poor, Poor Johnny-Boy," the voice was horrible, all oil and sugar slipping from a mouth that was no more than a ragged gash now. John's eyes no longer shone blue but instead glinted like chips of ice in deep wells. His entire face seemed morphed into some grotesque mask, a fright-house mirror version of John Watson.
"He loved the war, you know? Not the doctoring part… no, no, not that. He loved the excitement and not knowing who would live. It's chaos. Choreographed murder and chaos set to the delicious tempo of mortar shells and singing artillery. Didn't you think it strange that a Doctor would come running when you said it would be dangerous? Shouldn't they work to keep people out of harm? Not our Johnny-Boy, oh no Sir-ee. He wants to see the blood. He wants to see the terror and the dying and the screaming, oh God the screaming-how he misses that. He's gone alright, left to let me take control and give him a nice present of good old-fashioned blut und eisen. And I'll be starting with… you,"
Sherlock awoke thrashing in his bed, still hearing the sickening crunch of his neck bones being crushed in John's grip. His skin was clammy, his sheets sweat through. Sherlock looked frantically around the room, not seeing anything out of the ordinary, and taking a deep breath when his eyes found nothing.
A/n- if you want a placating bit of Johnlock, click to the next chapter. My damned feels wouldn't let me end it there.