So, I wrote this as a birthday fic for my good friend shutyourcommiemouth on tumblr. She loved it. I hope you love it, too.
"I don't," proclaims the curly-haired man haughtily, in between coughs, "get sick!"
"Well, you're sick now," says the no-nonsense, balding man with the perpetual look of distaste. "So grow up."
Dr. John Watson looks up in interest. Not many adults refuse to get medicine for their minor illnesses.
He sees his coworker, Sarah Sawyer, start toward them and raises a hand at her. He needs a bit of a laugh about now and this man already amuses him. He starts toward them, leaning heavily on his cane.
"Hello," he says when he reaches them. "I'm Dr. Watson, and you are…"
"I am Mycroft Holmes, and he is Sherlock. He has bronchitis and he refuses to do anything about it," says the balding man.
"That is because I do not have bronchitis!" exclaims Sherlock Holmes. "I never get sick!"
Mycroft ignores (presumably) his brother. "He is a child," he tells John, and gives Sherlock a little shove toward the doctor. "Treat him. I will be back."
John stares after Mycroft's retreating back in shock. "Well," he says. "He's rather pretentious."
One corner of Sherlock's mouth turns up in a slight smirk. "Yes," he agrees. "He is. And I'm not sick, so I'll be going home." He turns to leave when John catches him on the arm.
"Are you a doctor, Mr. Holmes?"
"Sherlock, please. And no, why?"
"Well, I am, so I should check for any illnesses. Just in case," he adds on hurriedly, when he sees the stubborn look on Sherlock's face.
"You're thirty-nine, been a doctor for five years. Why not longer? It's because you've been abroad. Not on holiday, but rather because you're a military man. You were honorably discharged when you were wounded. You're married, or were; your wife has either left you or died. Condolences. You have a limp, which your therapist thinks is psychosomatic, and she's quite right, too. Your life is monotonous and you crave a bit of excitement. So the only question left to ask is, Afghanistan or Iraq?"
"W-what?" stumbles John.
"Afghanistan or Iraq?" asks Sherlock impatiently.
"Afghanistan," answers John. "And that has nothing to do with this conversation, so if you were trying to jar me by naming things about myself that I already know, then you failed. Come inside."
As he leads Sherlock inside his little office, he adds, "That was bloody fantastic, by the way."
"Really?"
"Yeah. Amazing, brilliant."
"That's not what people usually say," says Sherlock, sitting down on a chair.
"What do they usually say?" asks John, reaching for the stethoscope around his neck.
"Piss off."
John laughs, and soon thereafter, so does Sherlock.
~x~
Throughout the next few weeks, Sherlock keeps inventing illnesses so he can go back and see that doctor. Other doctors just prodded at him and told him he was a freak, but Dr. Watson didn't do that. He just gave him some medicine for his bronchitis and let him leave.
One day, when Sherlock comes in with "Italian mamba flu", John calls him out. "Sherlock, this doesn't exist."
"Does, too," he sniffs. John grins.
"First of all, mambas aren't even indigenous to Italy-"
"One migrated."
"-and mambas can't give you the flu."
"It bit me."
"Sherlock, if a mamba bit you, you'd be dead."
"That's irrelevant information."
John sits back and grins. "You know, I don't live here. You can find me at other places instead of coming here all the time."
"I have absolutely no idea what you mean."
John laughs. "I have a phone. You can call me. On my phone."
"I don't have your number," lies Sherlock, as if he didn't look it up the first time they met.
John just looks at him, and Sherlock concedes, "Okay, okay, I do."
"Want to go out for a pint sometime?" asks John.
Suddenly, the figurative lightbulb switches on over Sherlock's head. "I have a better idea."
~x~
The crime scene is a gruesome one - the man in question has been brutally murdered. He's balding, near fifty, and Sherlock finds it difficult to deduce any more, since the rest of his body has been sliced into pieces and the remains are scissored with blood. All he can see is that the man is lying on his back.
"Tricky one?" asks Lestrade, coming over to stand next to him.
"Mm," says Sherlock, staring hard at the mangled body.
"Looks like even the freak has bad days," chuckles Sally, exchanging looks with Anderson.
"Alright, Sally, what do you deduce from this?" Sherlock whirls and raises an eyebrow at her. She stares at the body with her mouth agape.
"I-I-"
"Don't know. Thought so. Anderson?"
"Well," starts Anderson, his grating voice full of self-assured confidence, "he's not been dead for too long, only a day or so, because-"
"No," comes a voice from behind him. Sherlock looks toward the source and his mouth turns up in that half-smirk.
"Who are you?" asks Anderson spitefully. John doesn't answer, but points his cane at the body.
"It's been at least nineteen days," says John. "Maybe longer. Look at his face-it's marble-like, that means his veins have pushed up closer to his skin, which happens four to seven days after death. It rained yesterday, and his body, although cut up is sticky and wet, and there are beetles and mites around it, right?"
"Yeah," says Lestrade, grinning. "Come closer, take another look."
"What-Inspector?" shrieks Sally. "Who is this man?"
"I don't know," says Lestrade, "but he sounds right."
"Dr. John Watson," says John, putting out his hand to shake with Lestrade's.
"Detective Inspector Greg Lestrade," grins Lestrade. "Pleased to-"
"Greg?" sneers Sherlock. "Greg?"
"It's my name," says Lestrade, looking at Sherlock with a hint of incredulity. John smiles, then hunches over the body and peers at the back of the dead man's neck.
"Body's been moved," says John. "Livor mortis at the back of the neck."
"That's just a bruise," says Anderson. "Probably got it in the altercation."
"No," says John. "Definitely livor mortis, can't you tell the two apart?"
Sherlock's half-smirk turns into a full smirk.
"Decay's happened very quickly for two weeks, suggesting the man was on the heavier side. His nails have fallen off, so two to three weeks is an accurate estimate and-and-yeah."
"Oh, God, we've got freak the second," says Sally.
"Shut up, Sally, that was brilliant. Do you know Sherlock?" asks Lestrade.
"Yes, in fact, I came to meet him," answers John.
"Well," says Sherlock, "with the information that John has so helpfully provided for us, I'll be able to catch the killer quickly. I'll text you the details, Lestrade. I'm leaving now."
And so Sherlock and John walk away from the crime scene. The last words Lestrade can hear them say are:
"Dinner?"
"Starved."