Sherlock walked back into the living room of 221B holding a glass of rum and eggnog, a concoction he found utterly disgusting, but it was an excuse to drink, and that was an opportunity he couldn't pass up.
Molly walked up to him, her hair in the same style it always was, parted in the middle, her face dull, lacking makeup and general appeal. "Hello." She said nervously, "How do you like the party?"
He rolled his eyes, "I don't."
"Ah, why's that?" She leaned in trying to come on to him, he guessed, she did that a lot.
He stepped away slightly before realizing it, "I'm not one for social events" he said, starting to turn back to the kitchen for another glass of rum and eggnog. Molly made a move to stop him, but he was already headstrong towards the kitchen.
John took hold of Sherlock's blazer as he was walking out, "How many of those have you had?" He asked in a cautious, hushed voice.
Sherlock rolled his eyes, "Does it matter?" He asked coldly, "I'll be having enough to get me through tonight without hurting one of your little friends."
John scoffed, he began to spit out a well crafted come back, before his girlfriend, Sarah, cut in, "You two are standing under the mistletoe." She giggled.
John went scarlet, "Sarah-" he started, before being interrupted by Sherlock's hand on the small of his back, he felt himself being lifted towards his flat mates sharp features. The next thing he knew his lips had met Sherlock's in a mess of surprise and utter romance. Each time his lips fluttered again Sherlock's he could almost feel his heart about to leap from his chest. This wasn't something he'd been expecting.
John Watson wasn't gay. He'd knew that from the start, in fact when Harry came out to him he felt confused about it himself, but there was never really any question about it. But there was something about this Sherlock character. Everyone found him sharp, assertive, unlovable, but John didn't see that in him. John saw someone who didn't really know how to deal with people, but he never saw that as a fault. It was something he'd gotten use to over the two years they'd lived together.
And this thought didn't help John at all. God, what was he feeling? And it wasn't just now, just this kiss, that was making him feel like he was being turned into jelly, it was like this every time Sherlock deduced something new out of him, every time he refused to eat or sleep for days because he was so close to solving a case, every time he even looked at him. Sherlock had John under some sort of spell.
John pushed him away, trying not to blush, and the entire room erupted in a mix of applause and laughter, a reaction he'd definitely expected, there's nothing a drunk crowd loved more than two drunk people kissing- especially when those people are generally thought of as coworkers, just friends.

After the party, John took down the decorations and put Sherlock's boxes back where they were yesterday. That was their deal. John could have his party as long as everything got taken down directly after. They didn't say a single word to each other while he worked.

That night John laid awake in his bed, a practice he'd taken to get use to. Sherlock was a puzzle to him, and not something you could leave untouched, unsolved, but someone who was just so intriguing that you couldn't help but ponder which pieces fit where.

Soon after he'd finally drifted off to sleep there was a knock at the door. When he woke up he realized he was sweating, then he reached for his face and realized he'd been crying. What was he dreaming about?
Then it came to him.
He was alone. In the pool. With Moriarty.
Sherlock never showed up. He'd never gotten the missile plans. He was at home. Jim moved closer. "Your friend never came." He said, his voice particularly sour.
"Sherlock doesn't have friends." John replied, feeling warm tears on his soft cheeks. Moriarty wiped them away. "What are you doing?" the army doctor asked, trying to make his voice hard, trying to keep it from cracking.
"You don't need Sherlock." Moriarty insisted, "You mean nothing to him. You're a pet."
He was lying. He had to be.
"Think about it." He continued, "You're here, strapped to a set of explosives. He knows you're here, and where is he?"
John shook his head, "Stop."
"What? He doesn't care for you. You're just someone to help with the bills." he started to circle around John, then he stripped off the parka.
"You're lying!" The mere volume of that was enough to shock both of them.
"He isn't willing to leave his flat to save your life. But what would you do for him?"
John shook his head. He knew the answer, and it scared him. He would go through hell for Sherlock. He would gladly die for him. And Jim must have known that.
John rushed out of bed. A place that was suddenly painful for him. He moved towards the door, Sherlock stood in the doorway, "You were crying in your sleep." He said, "I could hear it from the sitting room." His voice didn't sound cold at all. It was worried, almost comforting.
"I just had a bad dream." John lied, that dream was far, far beyond bad.
Sherlock looked at him, he obviously saw that he was lying, but he decided not to tell him he had, "Would you like a cup of tea?" He asked. John nodded.
Sherlock lead John into the living room with anticipation, which John didn't understand, until they got there. All of the decorations had been replaced, twinkling lights hung above them, there was a Christmas tree in the corner decorated with all the ornaments John had packed away. "Merry Christmas." Sherlock said, a hint of nervousness to his voice.
"It's so beautiful." John said, looking around in awe.
"You haven't seen the best part." Sherlock said, nodding his head upward to where a sprig of mistletoe hung.
This time John kissed Sherlock. They didn't have the pressure of so many eyes watching them, they didn't have the embarrassment of Sally and Anderson there to harass them for it. They just had each other and the greatest Christmas gift John could ever dream of.