hey guys! just got obsessed with a new series :D
i've only had the chance to see the episode once, so dont pounce on me for not getting any dialogue/action exactly right. but, since it's AU, i suppose it can be excused.
also, the thing with Watson and the doors, in my mind, he does not trip in the version where he shoots the cabby before anyone can take either of the pills, and is the defining moment where the storyline changes.

Click.

Sherlock Holmes looked at the small flame that had lit at the end of the 'gun'.

"How did you know?" asked the cabby/murderer.

"I know a real gun when I see one." Replied the consulting detective.

They sat in silence for a few moments.

"Well, this is a bit awkward." Said Sherlock finally. "I should get going." He cast one last glance at the two pill bottles on the table as he sat up. Such a tricky game, so simple, yet so complicated.

"Do you know which one it is?" the calm tone of the cabby stopped Holmes in his tracks. He let go of the doorknob and looked at him. "Do you know which one was the good pill?" pressed the cabby.

Sherlock knew better. In fact, he knew he knew better. And yet, like a magnet, he was drawn back to the challenge. To the mystery. To the table where two pill bottles sat across from each other.

He snatched the bottle in front of the cabby as he sat back down again.

"Interesting…" the murderer betrayed no emotion whatsoever in his comment, then turned and opened the bottle that Sherlock had shunned.

Doctor John Watson was panting, panicked, and in pursuit. He raced through the empty college building, slamming himself into doors and trying to force them open. "SHERLOCK!" he cried, and then raced down another corridor.

He had an awful feeling about this. Sherlock was brilliant and all, but he didn't like to think of what would happen if he were alone with the killer for too long. And Watson was SURE that that was where Sherlock was.

He was about to blast through yet another door when he tripped. As he climbed back to his feet, he glimpsed another door out of the corner of his eye. Ignoring the one he had originally attempted to enter, he charged through this new door.

Doors, corridors, doors, more corridors, how big was this college anyway?

oOo

Sherlock swallowed. A moment after he saw the cabby do the same.

The room was tense. Both men stared at each other, knowing that in just a moment, one of them would drop dead.

The moment was shattered as a door burst open. A rather horrified looking Watson stood just inside. His eyes fixated upon the empty bottle that Sherlock was turning over in his hands. "No…" he whispered.

Holmes looked calmly up at the cabby, apparently taking no interest in the doctor, and asked, "How long does it take before it kills you?" he asked, as if pondering the weather.

"About two min-AGH!" the killer began, before letting out a guttural cry and slumping to the floor, where he began to twitch violently. "But…only know…after…thirty s-s-sec…"

Both Holmes and Watson ran to the man's side. The latter trying to determine his exact condition, and the former simply stared. "I got it right, then?" he said, rather eagerly, considering that a man was dying.

"I underestim-mated y-you." Admitted the cab driver.

"Who do you work for?" questioned Sherlock.

The cab driver shook his head. Refusing to answer.

"You're dying, but I can still hurt you." Said Sherlock, stepping on him.

Watson winced at the man's pained scream. "Sherlock, is that really-?"

"MORIARTY!" screeched the cabby. And Sherlock jumped off of him. Watson could tell from the rather distant look in his eyes that he had retreated far into the depths of his own mind.

All three sat there for a little while. Until Watson was suddenly aware of the lack of whimpering. He looked down and checked the dying man's pulse. It was nowhere to be found.

oOo

The blaring police sirens echoed in both men's ears as Sherlock and Watson later sat on the back of a car. Watching as the police puttered about, looking very official.

Someone walked by and put a blanket over their shoulders. Watson glanced at the revolted expression on Sherlock's face and contemplated how very wrong this picture looked. Them sitting next to each other, a blanket over both their shoulders. It looked very wrong indeed.

Sherlock glared at the police chief. "Why do they keep putting a blanket on us?" he asked, fiercely.

"You're in shock."

"I'm not in shock!" he looked at Watson for confirmation, which promptly agreed and said, "Neither am I."

"Well, it's good for pictures." The chief wandered off.

Sherlock immediately removed the blanket, rolled it up and tucked it under his arm. He stood up and began to walk away.

Watson stood up as well and bounced after Sherlock. "How did you know which pill was poison?" he asked.

"It was the obvious choice." Replied Holmes.

"How so? It didn't have anything to do with his hairstyle or anything, did it?"
Sherlock rolled his eyes. "Your sense of humor is mediocre at best. No, it was because he was favoring the one in front of me, a brilliant quadruple-bluff!"

"What do YOU know about humor?"

"More than you may think."

they heard the slam of a car door, and Sherlock let out a low groan. "Mycroft…"

and so, it just goes on from here exactly (or almost exactly) as the original episode did. i'll be flipping this around on the next (and most likely last) time i update this story, so its the same setup, but with a character death. but i suppose you've already deduced that, havnt you? you clever, clever readers. ;)