Note: I'm not sure exactly how this is going to go… there will probably be subtext of John /Sherlock, but I'm not sure if John would leave Mary for him. If you want some definite Johnlock by me, check out Three Patch Problem (rated M).
Marital bliss suited John Watson, his stomach had expanded slightly and he wore reading glasses now due to large amounts of medical journals and newspapers and the occasional novel. He had a comfortable job at a hospital different to the one Sarah had worked at, had sex with Mary about twice a week, and was somewhat grateful that she didn't want children because he was fairly sure he wouldn't know what to do with them.
Occasionally he would put on Tchaikovsky, close his eyes, and think about an old friend. On those occasions Mary would come sit with him and hold his hand. She was petite with brown hair and large brown eyes and she smiled at him a lot, she had this special thing where she would stroke behind his ears until he fell asleep in a stupor. John hated it and loved it. He hated not being in control of his own reflexes, but he loved the contented look on her face when he woke up from a short nap in her lap with her hair in his face.
About once a month, John would quietly take a violin out of the case under the bed. He didn't know the first thing about violins, other than that the music was beautiful and you were supposed to rosin the bow. So he would sit there, the violin on his knee, the bow and rosin in his hand, applying it gently, in long even strokes. Sometimes he would cry. Sometimes he would put the violin under his chin. He sometimes considered dragging the bow over the strings, but he didn't want to hear himself play. That was not the point of the violin.
When John went into his violin fugue, as Mary called it, she did not sit with him. Usually she was out when it happened. When she wasn't, she would sit in the living room, waiting for the sound of her husband's shuffling gait. He would lean heavily on his walking stick as he walked in the room, looking down, and sit in the arm chair by the fireplace away from the sofa. He wouldn't meet Mary's eyes.
Despite having a limp, John still did the shopping. It is only psychosomatic after all, and the bags for just himself and Mary aren't that heavy. He's glumly aware of the paradox of the limp; he knows it's fake, yet he still hobbles. The pressure to run isn't there. The dullness, the normalcy is. He remembers… he remembers what he… Sherlock said when he was dancing for Moriarty "I can't be the only one who gets BORED". John's boredom manifests itself physically.
Mary made him give up the gun after he stopped helping Lestrade occasionally with cases. Lestrade visited him occasionally for a year after Sherlock's death, and occasionally asked him to cases, but John felt like he was the DI's lucky talisman more than any kind of help. Occasionally he'd say something brilliant, but usually it ended up as a false lead, heading to some iota of information that meant absolutely nothing to the case. Once Sally began referring to him as "The not-so-Freak" John stopped coming.
A soldier, even a captain, is useless without his strategist.
The sky is grey, and the clouds suddenly open up and rain a grey sheet of water on London. The wet plastic bag is sucked against the milk bottle. John swears, he has an umbrella but can't use a crutch and carry the bag and the umbrella the same time. He hunches his shoulders into the rain and barrels onward.
"Oh good! No time to talk, you need to come with me John or they'll get away!" The excitable voice behind him made him smile. Still so determined, stubborn, brilliant.
"Shut up Sherlock, I can't go gallivanting off after criminals, I'm married now! I have milk to bring ho…"
He turned around. There. Same coat. Funny, he knew Sherlock by his coat first. The collar turned up to his cheekbones and the curls plastered against his forehead by the rain. John promptly dropped the bag of milk.
"Oh really John, you're limping again? Of course you're limping again. And fat. Well, not too fat. You'll do. Here, take this gun, and try to keep up. Honestly, it seems that you deteriorate if I leave you alone for more than a few days."
John blinked, took the gun. It was deliciously cold and heavy in his hand. He looked up (curses, why do I always look UP) at his benefactor.
"Sherlock?"
"Come on John, you didn't think I'd die, did you?" Sherlock ducked down a back alley. John Watson blinked, dropped his cane next to the milk, and dashed after him.
"SHERLOCK! WHAT THE HELL HAPPENED TO YOU!"
"Fantastic, John! You're doing well, keep going!"
OF ALL THE ARROGANT, SELF SATISFIED PRICKS! THREE YEARS! THREE YEARS! You imbecile! I WENT AND GOT MARRIED!"
"I know! Why on earth would you go and get married? No wonder you're fat; you're stagnating!"
"SHERLOCK!"
Sherlock laughed long and low as he turned a corner. "Come on John! Murderers are this way!"
"STOP CALLING FOR ME LIKE THAT, I'M NOT YOUR BLOODY PET!"
"No?"
"I AM SERIOUSLY GOING TO THROTTLE YOU!"
A gun went off, and John gasped at the noise, so loud and close that his vision went white and he lurched off to the side almost automatically. Sherlock came to a sudden stop, and John bumped into him, grabbing at his coat to steady himself. Sherlock twisted around, put a finger to John's lips and hushed. "There is actually a murderer involved, so keep it down."
John grimaced, ducked behind a dumpster and checked the gun that had been shoved at him earlier to make sure it was loaded. "Next time you miraculously come back from the dead after three years, come to my house for God's sake instead of leading me on a moronic scavenger hunt."
"And have you sob all over me? Dull. This is much more interesting."
John's grimace turned into a smile. "Yes, it is. I missed you…this, you bastard."