Okay, since the following two prompts are so similar, I figured combining them would be the way to go. Y'all are stretching my creative muscles; I appreciate it!
Timeline-wise, since this is something of an alternative universe, we're not quite going with A Study in Scarlet as a first introduction, but we are going with 1882, just before 'The Adventure of the Speckled Band.' Since this prompt required… some difference, I couldn't exactly do A Study in Scarlet.

So. As usual, this chapter's warnings include all the typical nasty stuff you might see in a Sherlock Holmes story, including talking about war, crime, and the like.
This is ALSO a two-parter! This chapter will be part one.
POV? Oh, you'll see.
With that… on with the show.

From Domina Temporis: If Holmes didn't become a detective, what would he have done?

And

From Domina Temporis: If Watson didn't become a doctor, what would he have done?

221B, Three Degrees Left

In 1882, when the last dredges of the war had finally cleared up, and all of the country's men had been sent home, John Watson was at a loss as to what to do next.
As was often the case for men returning home from war, many found themselves unable to readjust to civilian life, especially if the changes they experienced in the war were permanent in their new civilian life.

For John Watson? That meant the gleaming metal that now made up his hand and arm up to his right shoulder, made of iron and the typical materials used to make the prosthetic legs he'd seen on the field when he was reporting.

Watson could barely remember how exactly he lost his arm, waking up in a field hospital two days later from an explosion and a group of medics huddled over him, thanking anything that they believed in that he awoke.

Fiery pain gripping at my arm… what happened? Where am I? He'd been moved to another hospital specializing in prosthetics, fitting his arm with one and sending him out again to assist the other war correspondents.

But now? I can barely hold a pen, let alone follow anyone into the battlefield. What use was a war correspondent without one of their arms? Since returning home, His train of thoughts had grown bitter and melancholy at the idea of returning home to nothing.

"Watson? Is that you?" Called a warm, familiar voice to Watson as Doctor Stamford wove his way through the crowd to his side.
The two had worked together before Watson went off to report on the war, and Watson could attest that he was a good man and a much-needed friend at the moment to bite back his bitterness for.

"Stamford! How are you, old fellow?" Watson asked, warmly clasping hands with the Doctor. He chuckled, glancing over his shoulder briefly.
"Me? I am fortunate to have good crowds for my practice, as everyone has some illness or another this time of year, though I'm happy to oblige to help them. And you, Watson?" He asked as Watson paused briefly, the words going around his head.

"I am looking for something to do, I suppose. Now that I'm out of the military, I have nothing to report on and no home to return to." He admitted as Stamford clapped a hand on his good shoulder.
"What fortune I ran into you, then! I have made another friend since you've been off, Watson, who is looking for a room." Said he.

"Truly? Someone is looking for a room at this time?" Watson asked as Stamford chuckled.

"Truly. Now come, come, I just hope you don't mind silence." Stamford said.

Indeed, the man did mean silence. The Diogenes Club was built on a rule of silence and non-socializing, and Watson… felt it to be grating.

Silence is dreadful, even like this. Do they not want to do anything?

Stamford had led Watson to a small room in the Diogenes Club, where two figures stood in the window: one lean and in a black suit, the other more corpulent, older.

"Ah, Stamford! I can see you've returned from the outbreak. Pray tell who you've brought here?" Asked the leaner one as Stamford nodded, gesturing for Watson to step forward.

"This is John Watson, war correspondent. He was just discharged from the army and has been looking for a room, like you. Watson? This is Sherlock Holmes." Stamford said as both men clasped hands.

"How do you do, Watson?" Holmes asked as Watson shrugged his good shoulder.

"Better now that I have a potential flatmate." Said he as Holmes chuckled.

"You've returned from Afghanistan, of course. Originally wanted to be a Doctor, but changed to writing when you realized your hands wouldn't keep up with you. Came here by train." Holmes said as Watson's eyes widened.

"You're correct, sir! But how did you know?" He asked.

"Passing hobby of mine, as is the same with my brother, Mycroft," Holmes said, nodding to the older gentleman. "As for rooms, I have an eye on 221B Baker Street… which we should be able to share reasonably. Let me ask you this first. I am a violinist by trade; does music bother you?"

"No, not at all." Watson shook his head. "I spend most of my nights writing… something, anyway."

"I smoke. Several pipes and I will get into moods where I do not speak for several days. Is that a problem for you?"

"No, I smoke ships myself, and keep a bullpup," Watson said, as Holmes grinned at that.

"Well then, Watson, I believe we have each found ourselves a roommate."

As it turned out, "violinist by trade" meant Sherlock Holmes was a performer at the Old Imperial.

He often went off to perform at night and frequently offered free admission for Watson, who declined each time for now, at least.

Was it petulant? Perhaps. Watson was admittedly trying to get used to being a civilian.

Five days into sharing space, Holmes was charming to live with despite Watson's struggle to adjust. He kept to himself when he was sour but often entertained Watson with his hobby when he wasn't writing.

Or attempting to. Watson grumbled again when he dropped his pen, gritting his teeth as his prosthetic seized.

"Watson?" Holmes appeared around the corner, frowning at his companion's groan when he tried to bend over. "Do you need a hand?"

I'm not made of glass! Watson wanted to spit but relented at the concern in Holmes's eyes.

"I suppose I do." At Watson's word, Holmes stooped down, picking up his fallen pen.

"Do you also need it with your arm?" He asked.

Watson would have liked to answer yes when Mrs. Hudson entered the room, followed by a young woman crying softly into a handkerchief.

"Watson? This lady here claims to know you and has been looking for you." Mrs. Hudson remarked as Holmes glanced at Watson curiously.

"She does," Watson said, rising out of his chair. "Mrs. Lowell, please, come sit. Holmes, I confess I must explain. Before I went off to the war, Stamford and I ran a… help column of sorts."

"A detective column?" Holmes asked, and Watson couldn't help but startle, flushing.

"Yes. Of sorts. Not anymore, though. Though… to some, I am still a bit of a detective." Said he as Holmes grinned.

"This has gotten intriguing, Watson. Will you be so kind as to let me sit in with you?" Holmes asked.

"Oh, certainly." Watson nodded to a nearby chair as Watson sat across from his client, who sat down, trembling.

Holmes sat near them, silently passing a cup of tea to Mrs. Lowell.

"Now, tell us everything," Watson said. "This is Mr. Sherlock Holmes, you can trust him."

"I won't divulge a word," Holmes promised. "Whatever you tell Watson will not leave here."

Mrs. Lowell nodded as she collected herself with a shaky inhale. "Well, as Watson knows, I have a daughter." Said she, her fingers agitating over the cloth handkerchief.
"With the late Mr. Lowell, yes," Watson said as he leaned forward, intent on her every word and in a soothing gesture. "What has happened since he passed?"

"Well, my Julia has been… agitated lately. Said she wanted to get to know her father, but he died, so she said she'd do the next best thing. I remember she said that someone she just met knew her father—" Mrs. Lowell sobbed. "She disappeared, Watson, and she hasn't returned in two days. Scotland Yard laughed me out of their office, and I did not know who to go to."

"Where did you last see her?" Watson asked, retrieving his notebook with his good arm. Holmes took it instead, looking back at Watson.

What is that look? Watson wondered as Holmes tapped a finger against the page. Is… he asking if I need notes taken?

Watson offered a slight nod, returning to the distraught widow. "Well, over dinner. Last night, and then she said she was headed into the city." Said she.

"I'll get your daughter back," Watson said softly as Mrs. Lowell peeked up from around her handkerchief.

"Truly? But you said you're retired, Watson; I won't force you." Mrs. Lowell said.

Watson shook his head again, getting to his feet. "I might be, but I can not ignore your need." Said he. "Tell me if you have any updates or if anyone comes forward."

Mrs. Lowell grasped Watson's hand, tears springing back into her eyes. "Thank you, Mr. Watson, truly!"

I guess my old life returned to me… for better or worse.

I must digress that when I took lodgings with John Watson, former war correspondent, I did not take him to be a retired detective.

Really, my dear boy? You never thought he'd have the makings for it? Mycroft would probably have said as I shook my head.

Watson presented himself as a challenge, indeed. He had mentioned that he wanted to be a Doctor at one point, but his hands had failed to work to the standards medical men held themselves to.

Now? He carried himself with the air I'd grown familiar with of soldiers: half-rigid posture, a slight, vacant look in the eye, and biting back the pain from old war wounds. Then there was the matter of his arm, a prosthetic, new(yet slightly haphazard in construction) and recently polished by the hospital he'd returned from.

Detective? No. He initially seemed just a simple writer.

I knew that he was hiding back his pain from me, but for what? I had two theories. One that he knew I was a performer at the Old Imperial and thus held some sway as a 'celebrity.'

Did he see himself as a burden to me? Second, was that he was stubbornly used to taking care of himself, regardless of the degree of pain he was in.

Either way, I resolved to learn from Watson and care for him better. I might have once considered becoming a logician or a detective like him, but the art in my blood changed forms.

It is a passing hobby, nothing more. But for Watson, it was his career at one point, besides being a war correspondent. And if he felt as though he were a burden to me, or half a man with only one arm—then I would be his other arm.

"Why did you become a detective, anyway, Watson? You and Stamford?" I asked.

Watson glanced at me, offering a hint of a thoughtful smile—the first I'd seen in five days.

"A kindness. So many people reached out and asked newspapers, asked Scotland Yard, and never got an answer-back, like Mrs. Lowell. So, we thought we'd provide an answer. I have a lot of connections from my writing, and Stamford was always the brains behind our operation." Said he. "And we worked in tandem to solve cases or give answers. We might not have done much, but it gave people hope."

And Watson, you have an exceedingly kind heart.

"What stopped you? Besides the war?" I added as Watson was finishing getting dressed in his city wear.

"Despite my reputation, I never said we were successful. We don't have a head for deduction, like you do." He said.

"But you will still go out and try to find Julia Lowell? Just fresh off of the military?" I asked.

"Certainly. If not me, who else? Scotland Yard?" Watson's gaze bore into mine, slightly incredulous.

A new feeling arose in my chest as I also got to my feet, grabbing my hat.

I had only identified it twice before in my life. Once, when I aided Mycroft in building the Diogenes Club and then when I discovered Watson's prosthetic arm wasn't functioning as it should.

I didn't just want to aid him. I wanted to do my due diligence in this endeavor.

He does that much for the London public while Mycroft and I sit in the Diogenes Club!

"Watson, will you permit me again to come with you?" I asked as the war correspondent, former detective, and current detective looked stunned.

"I thought my profession bored you, so you never became one yourself. Art in the blood, as you said." Watson said.

"I might not have the same interest you do in dealing with these sorts of things or Scotland Yard, but I can not deny aiding my new companion is what intrigues me," I said.

Watson grinned wider at that, opening our door. "Well then, Holmes. Time to step into my life."

And that's it for part one. Yeah, needless to say, this sprung forth creative output like I haven't had in a while… and it was initially going to be War Correspondent! Watson and Violinist! Holmes, but my brain went, "Oops, Role Reversal AU," so I came up with this instead.

Domina Temporis, if you're reading this, what have you done? (I'm joking, but I adored tackling this prompt!)
In this world, Watson was once a detective alongside Stamford(I decided to give him some love, too), whereas Holmes found the idea of dealing with Scotland Yard and the world's problems to be a little… too much. As such, Holmes is a lot more in tune with emotions here than he normally is.
Prosthetics have been basically around forever! Victorian prosthetics were made with iron, rubber, and other materials, as well as wood, so I thought it'd be interesting to give our Watson a prosthetic arm in this world.

However, Watson's prosthetic is... slightly faulty, going back to his old war wounds in normal canon.

Lastly, my references this time around: 'A Study in Scarlet,' 'The Adventure of the Greek Interpreter,' 'Why Did the Detective Cross the Road?', 'Frostbitten,' 'The Things That Go Bump in the Night,' 'The Adventure of the Solitary Cyclist,' and, of course, partly the Granada adaptation of 'The Adventure of the Greek Interpreter.'
Next chapter: Part two of this universe. Hope to see you then.

Cheers,

Blue