This fic starts at the pool scene when Sherlock walks in, and then John enters. You may want to rewatch the pool scene before reading this, but be warned, it makes it harder to picture John saying some of the things Jim says. Okay, enjoy. :)

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"Evening."

John had stepped out of the dressing room.

John was standing in front of him.

He smiled. It wasn't his normal smile.

He was dressed up. Suit and tie.

"This is a turn up, isn't it, Sherlock?"

"John..." Relief, fear, worry, confusion, shock? His feelings were so muddled up he couldn't tell up from down. But one thought made itself very clear: No, this wasn't right. "What the hell-"

"Bet you never saw this coming."

Not-right John shoved his hands in his pockets. Sherlock just stared, unsure what to think.

"Nice touch this. The pool. Where little Carl died." Not-right John tapped his foot.

"What are you talking about?" His words trailed off into breath.

Not-right John dropped his head with a small laugh, so that it looked like he was grinning at his shoes. Thumbed his nose and licked his lips. All very different mannerisms-apart from the licking his lips. But even that seemed strange and unusual the way he did it.

"I'm assuming—hoping really—" he coughed, "that you've realized by now that I'm not John Watson."

Surgery. Must be plastic surgery just to throw him off. Using the shock factor. Sherlock tried to pull himself together.

"Jim Moriarty," Not-John informed him. "Hi."

Sherlock said nothing, still staggered by the similarity between the two Johns. They had gotten every single line, every pore, exactly the same. And their height, and their hair. Every hair perfectly in place. Doubt began to muddle his brain again but he pushed it away, deciding that this Moriarty fellow was obviously extremely wealthy. Real-John was safe at home or Sarah's house or something.

"Oh don't be stupid. This is what I really look like. No plastic surgery. That would be a tedious waste just for the look on your face. No it wouldn't have been worth it at all. I thought of something much better."

Another absurdly disturbing grin. Even the teeth and eyes were the same...

"Sherlock, I am your John."

He felt his heart sink. Everything seemed dim and murky and it was hard to breathe, like they were suddenly underwater.

Yes of course. This was too good to be the work of doctors and knives. This was the same person. But altered. Drugs. He must have John drugged. Or hypnotized. The brain could be highly influential if-

No that was stupid. What was going on?

"But I'm not John. John isn't real. I'm Jim Moriarty."

Sherlock ignored the man's words, dubbing them too cryptic to riddle out before he had finished decoding the rest. Nothing was making sense!

Something was wrong with John, that was for sure. He was too cold, too detached. Sherlock closed his eyes and shook his head.

"John, stop—" he started. The man before him cut him off harshly.

"John Watson doesn't exist, Sherlock. I made him up. His family too. Harry and Clara? All made up. Even fixed the phone to make it look like the sister was an alcoholic. I call that character development." John—or not-John—grinned toothily. "See? We even paid off your friend Mike Stamford to pretend to know John and introduce him to you. You'd be surprised how quickly people will betray each other when there's money involved..."

The realization hit him in waves, each so much bigger than the last, like a tsunami.

His heart stopped for a moment. His stomach dropped. A frost seemed to settle on him. He forgot about his gun. He tried to swallow but his throat refused to work for him. These were the physical effects of Sherlock Holmes being torn apart emotionally.

He wished he could believe the man in front of him was making this all up—perhaps that John was playing a joke on him and would at any second smile his regular smile and say 'gotcha!''—but the trouble with knowing what's going on in anyone's head at just a glance is that he could pretty much tell when people were telling the truth. And this...John was telling the truth.

And that smile was killing him.

"Oh come now, don't be that way. You should be flattered I spent so much time on trying to destroy you. I'll always have a soft-spot for geniuses like me in my heart, mydear."

It was that exact moment when Sherlock vowed never to trust anyone again-no matter how kind and good and understanding and fucking genuinethey appeared.

Of course, he didn't live long enough to keep that vow.

John-Jim. Jim Moriarty killed him before he could recover from the shock. With a crack like thunder, his head was snapped backwards as the bullet hit him straight between the eyes. Sherlock lay in a puddle of chlorine water and blood by the edge of the pool. Quite a beautiful death in fact. Very fitting for Sherlock Holmes. A romantic end to a fantastic story. The story of the most brilliant man in London. In the world.

Jim stood statue-like, arm still raised, gun in hand. This was how he grieved his kills, however brief that grieving period may be. It wasn't out of remorse so much as respect for the dead.

(Jim may be a vicious psychopathic criminal, but that didn't mean he wasn't a good boy.)

Respect, especially, for this man, who was so very nearly a god with his intellect. Every other human in this sad, little, insignificant world paled in comparison.

Finally he walked over to the body, leaning over the lovely, ashen corpse.

"Pity I had to kill you." He cocked his head to the side. "Complete waste of talent, but I know how great a threat you are to me. After all, we've been living together for months."

Jim laughed up to the ceiling. The noise echoed around the pool, delightful and sinister. He put his empty hand in his pocket and turned away. His shooting arm with the gun was limp at his side. Sebastian would be waiting with the car in the alley.

Of course he had had snipers ready to fire if it hadn't all gone according to plan, but it had. And the look of betrayal and hurt on the tragic detective's face had been absolutely delicious. He was glad he recorded this kill on tape. He would watch it over and over and feel that power-rush again and again.

A man so like a god. And Jim Moriarty had destroyed him. Not just by putting a bullet through his head but by breaking his heart. And what did that make Jim?

"I am a god," he whispered to himself. And he smiled, pleased with himself.

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