Here is the second assassin AU prompt idea. Kind of a common one I suppose, but I've always wanted to give it a try. So here goes! Enjoy!
Sherlock would never admit to the fact that he had grown comfortable with having John Watson in his life. That he was used to him, and that the lack of his presence unnerved him to no end.
Still there were some things he just had to do without the good doctor, such as facing Moriarty to end their game of chess once and for all. Yes, Sherlock had to leave John home for this one. He'd clearly argue against it, say it was too dangerous and try to keep Sherlock from going. Insisting on returning the Bruce-Partington plans to their rightful owner and letting the police handle the unseen criminal mastermind. As much as Sherlock loved to hear John worry about him, he couldn't have him interfering.
When he got home surely he would get a lecture, maybe John would tell him how valuable his life was and then scold him for endangering it. He'd never had anyone do that before, he would so often dance on the line between life and death and no one would give him anything but a look of disbelief but then suddenly there was this man that cared about whether or not he lived to see another day. A man who told him he had to eat proper meals, and get enough sleep, it was irresistible and miraculous.
Sherlock knew he was in love with John Watson, but as he had no experience with that emotion he was waiting to act on it.
Maybe he'll make a move before me, make it easy. Otherwise I might have to just ignore it for the rest of my life. Sherlock thought. Of course John did make a move first.
He moved right into Sherlock's field of vision.
"Evening." John's voice was cool, and his face showed no shock or fear. Sherlock's heart almost stopped, confusion covered his face and panic wormed its way into his body. "This is a turn-up, isn't it, Sherlock?" John asked, laughing quietly. "Bet you never saw this coming..."
"John?" Sherlock asked, and then he mouthed as if his voice had left him: what the hell...?
"Actually, for these past few days you've been getting to know me as "Moriarty"." John chuckled. "I can't believe you nicked my own gun to come face me, really, Sherlock? How immature." He said, gesturing to the pistol Sherlock had concealed in his pocket. Sherlock pulled the pistol now, but he held it at his side reluctantly.
"John...is he making you say this?" He asked, his voice shaking. "Like he did the others...is he making you talk to me?"
"There is no him." John shook his head. "There is only me."
"You're lying." Sherlock himself lied, as he knew for himself at that moment that John Watson was indeed betraying him and had been all along. It was so clear in that moment, that he wondered how he had allowed himself to be fooled for so long.
"Poor lonely Sherlock Holmes." John shrugged and sighed. "So lonely he even took his own worst enemy under his roof." He raised a hand lazily towards the roof, the pool water was lapping softly and sending reflections all over the walls in a way that would have been soothing under different circumstances, John snapped his fingers and a million red dots appeared over Sherlock's vitals.
"I really can't allow you to continue, its been fun and all but, you have to die." John's eyes were unnaturally cruel.
"Oh yes..." Sherlock looked at his feet. "I know."
"Yes, the clever genius detective would know." John smiled. "But you just weren't clever enough."
"Human error..." Sherlock's words came out on a single breath. "It seems even I am susceptible."
"Everyone wants friends." John's mouth was a thin line. "Even sociopaths like you."
"Well if I am to die, I think I should make it quite clear that I was seeking something a little more than friendship." Sherlock admitted, which he found odd. He always had the last laugh, always managed to make the enemy cringe even if he was in their grip. So why was he giving John...Moriarty...even more power?
John raised an eyebrow, and looked at Sherlock for what seemed like a lifetime.
"...You loved me?"
"I love you." Sherlock corrected the tense. "Of course I do, you're a psychopath and I'm a sociopath it's a match made in heaven and this whole time I never knew...stupid..." He felt hot tears burning at his eyes, but Sherlock Holmes did not cry so he blinked them back and faced John with clear determined eyes. "Are you just going to stand around wasting time or are you going to kill me now?"
John gave Sherlock a curious look, the look a cat might give to a mouse that bit it. That odd mix of pain and confusion. Then he raised his hand slowly and once again he snapped. The red lights vanished. Sherlock felt the pistol heavy at his side, but refused to lift it.
"Until we face each other again, Holmes." John said, and Sherlock ached to hear John call him by his first name again. "You won't be so lucky that time."
John turned and exited the pool area, leaving Sherlock alone with his thoughts. Sherlock's knees gave out and he collapsed onto the floor in a sitting position. He clutched himself tightly, dropping the gun in his haste to hold himself tight as though he was falling apart.
"Human error..." He repeated. "Perhaps I am not the only one that has fallen to it..."