The Seeds of Doubt.
A/N: This is my first Sherlock story! I wasn't expecting it to be Sally-centric, but this is where the inspiration struck. Enjoy!
Sally Donovan knew that one day a dead body would be found and Sherlock Holmes would be the one responsible. What she didn't know was that the corpse would be the detective himself, or that it would be her fault that he was dead.
Moriarty had told her that the others usually needed coaxing; threats or bribes thrown at them before they agreed to his meddling, but that he was impressed with her willingness to co-operate. She told him that she would love to humiliate the supposed genius and that no bribe would compare to the satisfaction of knowing that smug smirk would be wiped off his face, even only temporarily. He giggled as only a psychopath could, clapped his hands thrice with glee and set to the plan. It was meant to be a test run. If Donovan could convince Scotland Yard that Sherlock was a fake, Moriarty knew it would be as easy as taking candy from a baby to fool the rest of the world.
Sally believed that she was the only one, apart from Sherlock, who knew the truth about Moriarty, and this made her feel powerful. Dominant. Formidable. She had one-upped the entire nation, simply by spreading the seeds of doubt within her colleague's minds. She'd watched the seeds grow into flowers of distrust and suspicion, bright and glaring with the lie she'd created. She hadn't even needed to give proof, only insinuate that he might have something to do with the kidnapping. To Sally, the genius in her performance was superior to Sherlock's, her mind superior to his, her actions better in every way. She was bringing the God of deductions down to his knees, and it made her feel elated.
That is, until she saw his mangled, blood-stained corpse lying lifeless in the morgue, piercing grey eyes boring holes into her skull. The same grey eyes that had astutely deduced every facet of her life down to the detail of her activities with certain members of the forensics team now matching the cold slab on which he rested. She felt bitter; the memory of his taunts tinting her perception of his genius red so even in death she felt animosity towards him. But even dead he looked suspicious, as if he knew exactly what she was doing from beyond the grave. She realised, with a rush of emotion, that her actions had directly led to this, that if it weren't for her, Moriarty might have been the one she was looking at, and that the world would be rid of the psychopath. The weight of her betrayal hit her and she fell to the ground, gravity pulling her down as a punishment for her treachery.
Now, as she watches Doctor Watson walk slowly, carefully, his cane barely containing his limp which threatened to topple him over; his face blankly staring at a marble headstone – as cold and unyielding as the man himself once was – Sally wonders if Moriarty asked her to be his guinea pig for a different reason, something other than what she'd thought. She attempted to tap into the psyche of the psychopath and the realisation of his true motive scared her more than his sardonic smile or his eyes that burned with malevolent delight.
He was punishing her.
Despite his unadulterated hatred for Sherlock, the respect that Moriarty had for him and his genius was obvious even to the simple mind of Sgt Donovan. Throughout the years of their relationship (if you could even call it that), Sally had constantly undermined, belittled and at times feared Sherlock's intelligence, and Moriarty had decided that because of this, it was up to her to put an end to the 'freak'. He wanted her to face the devastating guilt of killing the most dazzling man on the planet because it was her. She had reduced him to this. To suicide.
It was the most brilliantly sickening (or sickeningly brilliant) plan she had ever witnessed, one that Sherlock would have been proud of. But now he wouldn't, couldn't, never would know the truth of her involvement, and that left a hollow in her heart that would never be filled, because he was gone. Cold.
Dead.