1) Experiment.

The first time Sherlock had heard of the mistletoe tradition (at least the first time that he didn't delete it right afterwards) was long before he and John were together as romantic partners as well as work partners.

It was just another day. Sherlock didn't have a case on so he was experimenting at home while John picked up some hours at the surgery. A recent case had involved the use of different plants to throw off the trace of drugs used in abductions, which meant Sherlock wanted to test how multiple plants affected multiple drugs. Today's plant in question was mistletoe. All over the flat Sherlock had sprigs of the leaves drying, including along various doorways.

John, always tired after a day full of coughs and sneezes, sniffles and wheezes, barely noticed it at first. Until he found himself face-to-face with an excited consulting detective, mistletoe directly above where Sherlock had him pinned against the kitchen doorway. Carefully, he tried to squirm away as Sherlock explained his breakthrough.

"The mistletoe, John! It can cover up the odors of- John what are you doing? I'm trying to talk to you." John stopped trying to break free and looked up at his flat mate.

"You're kidding, right?"

"What? Do I smell repulsive? Did I get something on my hands?" Sherlock did a quick glance down at his immaculate shirt, which gave John a chance to escape his grasp.

"No Sherlock, you're fine. It's just the mistletoe."

"What about it? I know you're not allergic, Mrs. Hudson's had some in her flat before and you were fine."

"No, I'm not allergic."

"Then what?" John heard as Sherlock's voice went from merely inquisitive to frustrated and impatient.

"The holiday tradition of kissing under the mistletoe? Surely you've heard of it."

"Not that I remember, no." Sherlock looked perplexed as he searched his brain for any inkling of the tradition. "It sounds plebian. I probably deleted it."

"Probably," responded John with a mental eye-roll. "Just…clean up the kitchen, yeah?"

Sherlock just shrugged, already contemplating what else mistletoe could cover up at a crime scene.

2) Shopping

The next time our boys encountered mistletoe was a few months later while shopping. Sherlock's experiment at the moment was trying to figure what was going on between him and John and so he was spending as much time as possible with his blogger (the more data he could obtain the better). Only in the name of science- and John's happiness, although he'd never admit that- would Sherlock go for the shopping.

It was early December, which was well into the holiday season for stores. John just wanted to get in, get everything, and get out. The last thing he expected to see was mistletoe hung over every aisle.

"Fantastic," he muttered, grabbing a basket and trying to decide the easiest way to get finished without any remarks about how he and Sherlock, apparently a couple in the eyes of the world, should take advantage of the plethora of kissing opportunities.

"What's fantastic?" asked Sherlock, mentally deducing all of the boring shoppers in order to keep his mind occupied.

"Er, I just don't like the looks of these crowds," John said, only half lying. "Do you think you could get this part of the list without causing a scene?" He tore his list and held out one piece for Sherlock. Sherlock just looked at it.

"I'm not a child, and I know what's on the list." And with that he went off, leaving John to shop without worry of "plebian" traditions and himself to shop with a strange feeling in his chest at not getting to spend the time with John.

3) Case

The third time mistletoe showed up was the next year, just after John had decided that being a couple might not be so bad. Sherlock, having known how he felt since he found time to analyze his feelings from the shopping scenario, was more than willing to give "them" a try.

They were on a case, another one full of disappearances, all children ("so dull, John. Why would people actually want to steal a small human, if not to get something from the parents? It'd be so tedious to take care of them afterwards." "Sherlock, there are more reasons to want a child than just ransom money." "Like I said, dull.")

Long story short (we'll save it for a rainy day), John and Sherlock wound up tied together underneath mistletoe. Lestrade never let them live down the fact that they were saved by the kid they were supposed to find and he especially didn't let it go that they were technically supposed to kiss, given how they were situated. What he didn't realise was that Sherlock wanted nothing more than to pull John close and enjoy the tradition for once, plebian or not.

And maybe, just maybe, children weren't all that bad, thought Sherlock.

+1) Hamish

The time when they actually followed through with the kissing tradition was because of Hamish. He was about 5 at the time, and very excited for Christmas that year. In the weeks leading up to the 25th, Hamish would only ask for Christmas stories at bedtime and Sherlock took this chance to educate him about the different winter holidays and traditions around the world. One tradition he left out was the one that included mistletoe.

But Hamish wasn't just learning from his family anymore. School was supplementing the knowledge Hamish was receiving at home and one of the other children had mentioned the kissing tradition when the class was sharing Christmas traditions that they each had at home. So the idea was planted in Hamish's curly little head, ready to grow into fruition on Christmas morning.

Now, it was a rule at 221b that Hamish couldn't wake up his Daddy before 6:30 unless it was an emergency, but Christmas was special; after much convincing, Hamish had talked John into a 6am wake-up call. And so at precisely 5:57 Hamish crawled out of bed and crept over to his crayon box. From inside he pulled a sprig of mistletoe (he had traded a few homemade cookies for it from the girl whose family always had mistletoe). Then he quietly snuck down the stairs and into his parents' room.

Without making a sound, Hamish climbed up the foot of the bed, careful not to crush the small plant in his hand, and snuggled in between Sherlock and John.

"Daddy," he whispered, nudging John first and then Sherlock. "Father. It's Christmas!" Sherlock yawned and moved closer to Hamish.

"So it is. Merry Christmas, little one," He murmured. "Merry Christmas, John." John mumbled something back and Sherlock laughed quietly.

Hamish, by this point, was done with lazy morning greetings. He stood up on the bed, holding the mistletoe over his dads.

"Get up! You have to kiss." John and Sherlock both looked up at their son and then looked at each other, amazed at how the little plant was a welcome sight when held by their son. John pulled Sherlock closer and gave him a soft peck on the lips. "Merry Christmas, Sher."

"I was wrong," Sherlock said with a grin, "children are anything but dull." John laughed and pulled Hamish back down so he and Sherlock could lean in to kiss their little gift.

A/N: I was going to do a 5 + 1, but that clearly didn't happen. Whoops.

I do have an idea for the case with the kidnappings (I have no idea if mistletoe actually covers up drug traces). Maybe I'll post it on a rainy day. ;)

Sorry I didn't make my weekly Sunday deadline. Family Christmases and all that. But anyways, Merry Christmas! 3