Sherlock series 3 spoilers. Basically just a drabble beceause I have a lot of feelings about the Mary is Moran Theory.
They should have known, really.
Perhaps Sherlock did. Read it in the curl twist of her mouth, the flash of teeth (canines and molars and all) every time the name Moriarty flitted across the telly screens or in Sherlock's mouth. Sherlock said those four syllables with a sneer, John with a clutching adrenaline, but Mary - she said it with a smirk. Maybe he saw it in the flat expanse of her gaze when she said things like, "They had a file on him, you know. Where I worked," and, "He's really rather clever isn't he? More than Sherlock." (Never said the last one to Sherlock, of course, those words were only for John's ears.)
"How'd he do it," they'd all mutter with more gritted teeth than they did when talking about the suicide of a fake genius (fake suicide of a genius). Sherlock most of all, and Mary would say, "He probably had it planned far ahead." And then she'd laugh.
Sometimes, in the nights following Did You Miss Me, she'd go away, vanish with a gun tucked in her coat and a baby cradled in her body. John let her because John did it, too, without the baby but with the gun. Always the gun.
Mr and Mrs Psychopath.
Really, he should have known, but for all the beacon of light John Watson is, he really is quite dense.
Maybe a part of him did, he thinks now, with a gun pressed to his temple (always'd go down like this), and a baby that never made it out of a womb alive buried six feet down. Maybe he always knew. Maybe he didn't care.
He chose her after all.
Sherlock's standing not five feet away, gun held in his own hands and it wouldn't be the first time he'd killed somebody (for John, it goes without being said). He's not shaking and his face is blank and the sentiment spilling out of his eyes stays locked in his mouth. Do it, John screams to him in a universe that isn't this one. Go ahead, kill her. John's not sure he doesn't want that.
"Did you know, John," Sherlock says, bright eyes fixed on Mary. "When using a pseudonym, one tends to select a name that closely resembles their own." His eyes narrow, slightly, but there's a lilt to his words that only Sherlock Holmes could accomplish. "Morstan and Moran are rather quite similar."
"Moran's a common name," Mary breathes. "It means nothing."
"Oh, no, of course not," Sherlock replies. "Unless of course Jim Moriarty has his fingers in it. Then it means everything. Did you miss him, Miss Moran?"
"Oh, didn't we all," Mary says, a paint-by-numbers smile on her face. "It's been a fun game, Sherlock, we all had fun, didn't we John?"
John looks up at her, thinks that if he's going to die by the hand of someone he loves he wants to look them in the eye. The copper taste of blood in his mouth heavies his tongue. "The greatest of times."
"You know all he ever wanted was to be king," Mary laughs again. "We'll do it you know. Burn it all down."
"I do wish I'm around to witness that," Sherlock murmurs with all the candor of his older brother.
"So do I, Sherlock," Mary whispers and the gun presses further into John's temple. "So do I."
Somewhere in the night, a gunshot sounds.