Obvious
"It's bloody cold out here. Shall we go in?" the doctor asked, as he approached the detective.
"John, you ought to know by now how I feel about marriage."
John stopped in his tracks. If Sherlock hadn't already been certain of his deduction that John was planning on proposing, then his reaction would have been a dead giveaway. John's eyes widened to an almost comical size and his breathing stilled for a good four seconds. A range of emotions passed his visage: first shock, then misery, and lastly, fond exasperation.
While physiognomy, the science of judging human character from facial features, had never been Sherlock's strong suit, John had always been easy to read for him. Being in a relationship with the man for close to four years meant that Sherlock didn't even have to try anymore. So when John had started acting jittery a few days earlier, Sherlock had immediately known there were four possible explanations.
One: John had gotten fired from his job.
Two: Harry had, once again, drank herself into a stupor.
Three: John wanted to end his and Sherlock's relationship.
Four: John was going to propose marriage to Sherlock.
Then, around ten o'clock at night, the day before, right after the men returned back home after a case, John had asked Sherlock out to dinner. While it would certainly not be unconventional for most romantic partners to make dinner plans, it was highly unusual for Sherlock and John to make such plans. They ate - or in Sherlock's case, sat - at restaurants approximately four days a week, usually after having spent the day on a case. On the remaining three days, John liked to cook dinner at home. This preference for home-cooked meals most probably dated back to his youth, in which his family didn't have the money to dine out often. In conclusion, John didn't usually suggest dinner for dates, so this particular date must be quite special. All of this led Sherlock to believe that he would find out at dinner what John had been worrying about the past days.
When John arrived at the restaurant - he had come straight from work - two things became absolutely clear.
One: John had recently bought something expensive. This could easily be deduced from the fact that John had arrived at the restaurant wearing his best suit, which was usual, but having gotten it dry cleaned at a rather low price, based on the still rather obvious stains on his left sleeve. If John had indeed thought of this night as an important night - and Sherlock was quite certain of his deductions - then he would've gotten his jacket cleaned properly. He still worked as a general practitioner and his pay day was three days away. Between that and having spent an exceptionally great amount of money in an exceptionally short amount of time, John would not have any money to spare for frivolities such as his physical appearance.
Two: The expensive object was small and currently kept in the inside pocket of the aforementioned stained jacket. Quite obvious, really, as Sherlock had clearly heard the jingling of John's set of keys in his right-hand outside pocket when John got out of the taxi and quickly shoved his hands into his pockets for warmth. He usually kept his keys in the inside pocket, where they would be harder to pickpocket. Sherlock briefly entertained the possibility of a hole in the inside pocket, but the jacket was quite new and made of sturdy material, bringing the probability of that theory down to close to zero. So, naturally, if the keys were in his outside pocket, the inside pocket must've already been occupied by something else, something even more valuable than John's means to be able to enter his own apartment.
Nothing more valuable than an engagement ring. At least, to ordinary people. Sherlock was of the opinion that weddings are nothing short of a celebration of all that is false and specious and irrational and sentimental in this ailing and morally compromised world.
A minute or two passed in silence after Sherlock made his comment. At last, it was John who spoke. "Well, I suppose I shouldn't be surprised by your deductions anymore. I suppose I don't have to go down on one knee, then?"
"Don't be silly, doctor Watson. You of all people should know I am not particularly fond of grand showcases of affection. But your face tells me you were already quite certain that I was going to say yes regardless."
John smiled fondly at his new fiancé. "So, how did you know?"
"Your keys are in a different pocket and the left sleeve of your jacket is stained," Sherlock answered, "so it really couldn't be more obvious."
fin
Author's note:
Hello! Thanks for reading, I hope you enjoyed my short one-shot. It's actually the first Sherlock fanfiction I have ever written, so I do hope it's alright. If there are any enthusiastic Britpickers and/or other nitpickers out there, feel free to leave criticism. Of course, other comments are very welcome as well. Have a nice day!