John used to smoke, whereas Sherlock never actually has. He used the nicotine patches, sure. But only once has a cigarette touched his lips. He was sixteen, curious, and bored. And he'd never choked so much in his life.

John started smoking when he was twenty-two. He was in the service, under stress, of course, and needed something to do. It just sort of happened. He quit shortly after his mother passed away. He wasn't sure why he had the urge to quit, probably something cliché like life being too short, or something. He replaced smoking with other things, one being his bunkmate.

Sherlock always noticed the random moments John would pucker his lips and suck in. Of course he noticed. He was observant and spent 75% of his down time looking at John. It didn't take him long to notice.

"Do you do that because you used to smoke?" Sherlock thought it best to ask randomly than weave it in to normal conversation.

"Do what?"

"Pucker your lips like that."

"Like what?"

Sherlock demonstrated.

"Oh, that. Uhm, yeah. I did. When I was younger."

"How young?"

"I started when I was twenty-two."

"That's not that young."

"Does it matter?" John was snippy today. He did the lip thing.

"You do it when you're annoyed or trying to think."

"Do I?"

"Yes. Which means you do it a lot with me. Do I make you want to smoke again?"

"Sometimes, yeah."

Sherlock left it alone. He didn't want John to feel stressed near him.

Two weeks later, Sherlock began his new form of conditioning. Each time John sucked in, Sherlock would kiss him.

For two months this went on, this little pattern that John didn't know about. He'd suck in and Sherlock would kiss.

Then, they were on a scene and the conditioning more or less paid off.

Sherlock was yelling, "Think, John! Think very, very hard!"

John couldn't think. John's mind was crowded with too many thoughts and trails and dead ends. John was too stressed to think of anything else.

Then, John stood and quickly grabbed Sherlock. He forced his tongue into Sherlock's mouth as quickly and forcefully as he could. They stood tongue battling for a few minutes, everyone watching and quite uncomfortable.

Then, their kissing slowed and was beginning to be slow and passionate.

Which was even more uncomfortable.

Finally, John broke away and began shouting about some rubbish.

"Her skin, right there, it shouldn't be that shade of green. If she was decomposed, yes, but she's only been here six hours it wouldn't be that color. It had to have been something in the water where she began. Upstream, obviously, because her body flowed downstream. Additionally, I think the cut was made after she was already dead. Hardly any blood flow, plus the cut was probably made with something equally as unsanitary as the river. All of the other bodies have the same thing? Well, you're looking for the murderer near that rubbish plant up the river, he's got to be there. Were you trying to condition me?"

"Well done, John! And yes, I was."

"I told you to stop doing that!"

"Wait, he does it often?" Sally began to laugh.

"Shouldn't you all be off finding a murderer somewhere?" John yelled.

"Why are you upset?"

"Because now when I get worked up I'm going to have the urge to kiss you!"

"I don't mind."

"It's embarrassing!"

"To you."

"Yes, well. Uncondition me."

"Uh, I can't, John. That's the point."

"Dammit, Sherlock! I am not part of your experiments!" Then, John attacked Sherlock with his lips again.

This time everyone began to disperse, and John and Sherlock got a cab and kissed the entire way home, where they definitely kissed some more.