Set a few weeks after Sherlock's return. Slightly AU (Mary is not mentioned and John is living back at 221B)
Try as he might, John could not see what was so special about the shoe that Sherlock was inspecting. He waited patiently for Sherlock to share whatever information he had gleaned with himself and Lestrade. Minutes passed. More. Finally, Lestrade opened his mouth, only to be cut off by Sherlock.
"The tread of the heel is worn heavily on one side but intact on the other, suggesting either an odd gait or relentless pacing. His flat is immaculate and arranged with as much symmetry as is possible with the various furniture. Wrinkles in the cushions and bed are smoothed out, the linen looks regularly ironed. Pictures have been hung so the light falls on what must be his favourites first when the sun rises and his bookcase is arranged alphabetically. But as dust has started to settle on items that are obviously regularly used, it seems that he was losing interest in the strict order he has surrounded himself with."
"Meaning?" Lestrade was losing his patience.
"The victim was obsessive-compulsive and depressed, the latter being only of a recent onset. At the breaking down of something he considered important, he became unwilling to participate actively in life. In his isolation, his mental state rapidly deteriorated. For once, the apparent suicide really is a suicide." John felt a pang in his chest at Sherlock's last comment.
"What was it? What… pushed him over the edge, so to speak?" Neither Lestrade nor Sherlock notice John flinch at that particular turn of phrase.
Sherlock searched around quickly and pulled out a thin, crumpled paper booklet from the bin placed unobtrusively in the corner.
"Death in the family. A Mr Kyle Jennings… Physical resemblance points to brother." Sherlock murmured absentmindedly. "Died in a car crash eight days ago." He started flipping through the booklet.
"What are you looking for? If it was just a suicide, isn't that the case closed?" asked John
"There must have been something else. Loss of a family member wouldn't usually drive someone to this extreme, not unless they were particularly close or there was some other trauma, like the manner of the death."
"What, his brother getting his head smashed in wouldn't be enough for a mentally unstable man to kill himself?! No, there has to be something else to make it even worse before anyone could think of taking their own life!" John realised how hysterical he sounded after the words spilled out of him.
"It's not as if it would be the worst that could happen."
Lestrade shot a glare at Sherlock.
"What?"
John was furious. He opened his mouth to yell at Sherlock, then instead turned and ran out the door.
"John!" Sherlock called out. He turned to Lestrade. "What was that about?"
"You really don't get it, do you?" Lestrade's spat at Sherlock.
"Oh, I guess it's one of those sentimental things."
"One of those sentimental things? Sherlock, any human being will be affected by that! When someone that close to you dies, it's not just something you get over!"
"But what's John all worked up about? He didn't know either of these men."
"It's not about these two, it's about you! You did the same thing to him! Two years you were gone, two years, and it nearly destroyed him. And now you look at this man and say that that isn't the worst that could happen?"
"Look, I understand that it wasn't easy on John, but he took it as well as could be expected-" Sherlock was cut off by Lestrade's fist flying at his jaw.
"Took it well?! You idiot!"
"I said 'as well as could be expected'!"
"You didn't see him, Sherlock! He looked like you took half of him with you! You didn't get drunken phone calls at two in the morning or sit up all night listening to him mutter in his sleep. You didn't have to help him move out because he couldn't bear to be there anymore and see the blood on the plates he smashed in rage, or have to take away his sleeping pills and not only because they trapped him in the nightmares! You didn't sit for hours trying to get him to eat, or to talk, or even to move. You didn't see him nearly lose his job and you didn't see the scars appearing on his wrists! You never ran to the cemetery to see him sitting at your grave with his gun in his mouth!" By the end of his little speech, Lestrade had Sherlock pressed into the wall and was shoving his arm against Sherlock's throat. He seemed to suddenly realise what he was doing and stepped back abruptly.
"What was that?!" Sherlock coughed, gasping for air.
"I'm not going to apologise." Lestrade's face looked like it was chiselled out of stone. "But you are. Go after him."
For once in his life, Sherlock followed an instruction without arguing.
"John? JOHN!" Sherlock ran into 221B, panicked. What if what he had said was enough to drive John to… something drastic?
"Oh, what's all the commotion about?" Mrs Hudson looked through the doorway.
"Mrs Hudson, have you seen John?"
"He ran in just a few minutes ago. You know, I think he's gone and locked himself in his room! What's going on, Sherlock?" But Sherlock was already running up the stairs.
"John, I'm sorry! I didn't think. I was an idiot, I never meant to do that to you! Let me in, please, John, don't do this!" Sherlock banged once more against the door and sank to the ground beside the doorway. "I'm sorry. John, I am so, so sorry. I didn't want to hurt you. I didn't want to…"
The door slowly opened.
"It was." John's voice was barely a whisper.
"It was what?"
"The worst thing. You… leaving like that, letting me think-" he took a breath "Letting me think you were dead, it was the worst thing that possibly could have happened."
"Lestrade told me what it was like for you." They were both silent for a long time. "I put you through hell, John. I thought I was doing the right thing, I was choosing the lesser of two evils."
"Lesser? The lesser. That, that was the lesser evil?"
"Yes." For the first time since he ran out, Sherlock looked John in the eye. "As awful as it was, it could have been worse. The lengths that some people are willing to go to…" John shook his head.
"You think it could have been worse? You think I could have gone through more, like that poor bastard at the scene?" John's voice began to rise again. "I did this because of you!" As he spoke, he pushed up his sleeves, baring his arms to Sherlock for the first time since he'd been back.
Sherlock felt his throat seize up at the layers of scars, old and new, covering John's arms. His mind supplied facts he could well have done without - this one was from a knife, this a razor, this a hot stove. The depth and age were all too obvious. And there were at least three vertical cuts on each wrist, slicing directly through major veins.
SUICIDE ATTEMPTS, his mind floated up. MULTIPLE.
Sherlock fought back tears.
"Alright." He took a deep breath. "You show me yours…" Sherlock took his coat off and cast it aside. Then he rolled up his sleeves, showing only the smallest of his own scars. He looked away from John, unable to meet his eyes in his vulnerability.
John's gentle grip on his arm took him by surprise.
"Is this all of them?"
Sherlock didn't answer.
"There's more, isn't there?"
Still not meeting John's eyes, Sherlock slowly peeled off his shirt. For a couple of minutes, there was silence as John inspected the scars. Sherlock knew that his medical training left John with just as complete a picture of the original injuries as Sherlock had of his. Acid burns, whip marks, manacle chafing, flaying… Moriarty's operatives were well trained and very creative.
"So I'm not the only one who went through hell." John murmured.
Sherlock turned around and rubbed his thumb over John's forearm. "You did this because of me." He glanced at his own scars. "I did this for you."
For a long while, they held each other and cried, letting out all the pain each had suffered in their time apart. It would take time and effort, they knew, but they would make it. Both of them, each with the other to lean on.