A/N: Crossposted at my AO3 account, this is a super-late Sherlock Secret Santa present for Ansley. Enjoy!

John had become more or less accustomed to Sherlock's experiments. The limbs in the kitchen appliances, the petri dishes stacked precariously on the dining table – they had simply become part of the routine, the adventure that accompanied a life with Sherlock Holmes. No experiment of Sherlock's could surprise John – or so he thought.

"John, I would like to conduct an experiment. But I need your assistance."

"Sherlock, for the last time, you are not using my jam for part of your experiments. I don't care if it mimics the consistency of- "

Sherlock opened the small box he was holding. There was a ring inside.

"No John. How would you like to get married?"

John's first reaction was to contemplate dragging his flatmate to the nearest psychologist to have him declared certifiably insane. Other options included checking for signs of drug use and making sure that "married" wasn't some kind of nickname for a new cadaver or piece of laboratory equipment. As it was, John settled for just staring at Sherlock, mouth agog.

John had dated a string of women during his time at 221B, and Sherlock had remained as uninterested in romance as ever. Visitation rights at the hospital had never been a problem for them, thanks to the omnipotent hand of Mycroft. There really was no reason for marriage. Except…

John had always had trouble trying to define the relationship between him and Sherlock. They were more than flatmates, more than colleagues. They introduced each other as "friends," but the word didn't even come close to describing the ties that existed between the two of them. Forged from rooftop chases and post-case dinners, long nights at Barts and fights in the flat, theirs was a bond deeper than friendship or love. Husband, partner: weren't those words so much closer to what he and Sherlock shared?

And really, who else would he spend the rest of his life with? Ever since John had first laid eyes on the consulting detective, Sherlock had consumed his life – a brilliant tongue of fire leaving an indelible mark wherever it burned. Sherlock always came first. Before any date, before any girlfriend, there was Sherlock. To pledge his life to anyone else would be unfair, if not even downright cruel.

And then there was the ring. The ring really didn't signify anything. And yet, it was everything. Every bruise, every cut, every broken bone. Every case he had meticulously archived in his blog. Every day that John spent knowing without a doubt that he would follow his consulting detective to the end of the world and back.

So, with a grin, John nodded and slipped on the ring, taking part in Sherlock Holmes' greatest experiment. Because, after all, wasn't that what husbands, partners, soulmates did?