Author's Note: So here's my theory, which may have already been addressed by someone else. When Sherlock's in the Mind Palace after being shot in His Last Vow, Molly and Mycroft tell him to find something to calm him down so he doesn't go into shock. This is when we learn about Redbeard. But before Sherlock reaches Redbeard, Mary, in her wedding dress, appears behind a door with a gun. This leads me to believe Sherlock was originally searching for John. Of course Mary would be connected with John in the Mind Palace, as, until this moment, she doesn't have much of a role to Sherlock or the audience beyond "extension of John Watson." Sherlock can't separate the two, so he seeks out Redbeard, who is far removed from any of this.

All that being said, here's my take on what would have happened if Sherlock had found John instead.

Wild men who caught and sang the sun in flight,
And learn, too late, they grieved it on its way,
Do not go gentle into that good night.

-Dylan Thomas, "Do Not Go Gentle Into That Good Night"

The bloody sirens were going off again, blaring warnings that the entire operation was being shut down and everyone would do well to evacuate. It was really unnecessary. Sherlock would have to fix that after this was all over. Assuming he'd still be around to fix it, that was. Otherwise the klaxons might sound for all eternity.

Wouldn't that just be perfect.

In Magnussen's office, he'd made his transport fall backwards (per the committee's suggestion), and had returned his consciousness to the morgue in his Mind Palace.

"What the hell is that?" he yelled to Molly over the noise. "What's happening?"

Beside him, a dead body on a slab slid out of a cabinet. Sherlock looked down in horror: his dead body. Well, that was something else he'd have to change. Crisis or not, he could honestly do without the theatrics.

"You're going into shock," Molly replied. "It's the next thing that's going to kill you."

Brilliant. "What do I do?"

"Don't go into shock, obviously." And now Mycroft was back. Even better. "Must be something in this ridiculous memory palace of yours that can calm you down."

Sherlock stared as his brother, racking his brain. Calm you down…calm you down…

"Find it!" Mycroft ordered.

He didn't need to be told twice. Sherlock raced through the hallway towards a familiar door. He paused momentarily, a bit hesitant about who might be on the other side. Mentally he gave a quick reset command: temporarily relocate any information in that room acquired within the past year.

There. That should ensure some modicum of safety while the world was collapsing.

Sherlock reached for the doorknob, threw it open, and found…

…Doctor John Watson, sitting at his desk at the surgery.

"John!" Sherlock gasped, stumbling into the office.

The doctor jumped up, his face more horrified than Sherlock had ever seen (which was saying a lot, all things considered). "Sherlock!" he exclaimed in that patented "what have you gone and done to yourself now?" tone.

The detective fell to his knees just as John made it to his side, squatted next to him, and supported the younger man's weight in his arms. Sherlock leaned into his touch. He'd found his doctor. He was badly hurt, but he'd found his doctor, and John could fix him now, just like always.

"What's happened, Sherlock? What's wrong?"

"I've been shot, John," Sherlock explained, his words starting to slur. "They shot me, too…s'no fun, is it?"

"No…no, it isn't." Doctor Watson wrapped one hand around the back of Sherlock's neck for support, and held his wrist in the other. "Okay, your pulse is too erratic. You need to breathe for me, deeply and slowly." He took a deep, exaggerated breath for good measure. "Like that, yeah? Can you match my breathing?"

Sherlock could feel his breaths stuttering, his heart beating wildly and without rhythm. "I…can't…"

Doctor Watson squeezed Sherlock's neck. "Yeah, you can, you bloody genius. Breathe, like you've seen me do after a nightmare. Do like I'm doing right now." He was using his Very Good Doctor voice, the one reserved for patients and clients. It always kept them calm. John was brilliant at that.

Sherlock mimicked John's breathing. He concentrated on his friend's hands, strong against his neck and wrist. John was here. John was safe. Wasn't he? Sherlock knew there was something he needed to tell John, something he'd stored away somewhere, but for now…he felt his heartrate even out. Doctor Watson, still holding Sherlock's wrist, noticed as well and gave a comforting smile.

"Good, mate. That's very good."

Sherlock tried to smile back, but felt his face falter. Above, the lights flickered. Something new was happening. "John," he moaned, voice shaking.

Sherlock heard Molly's voice again, echoing through the hall. "Without the shock, you're going to feel the pain. There's a hole ripped through you, massive internal bleeding."

And oh god, but she was right, because the hurt came on so suddenly and so strongly that Sherlock sank completely to the ground, convulsing at Doctor Watson's feet. He'd been hurt before, loads of times. But it had never been this bad. Never this bad. Not even in Serbia, because they didn't want to kill him, just torture him until he broke. This was different. Serbia was just going gray around the edges of reality: this was darkness closing in from all sides.

Sherlock clutched at his chest and looked up at his doctor with watery eyes. "It's too much!" he gasped. "I can't take it!"

"Sherlock—" he heard John's voice, but it was real John, not John-inside-the-mind-palace. "We're losing you!"

Sherlock opened his mouth to say he was sorry, he knew he was giving up, he was so very, very sorry. But instead, he heard Molly's firm order: "You have to control the pain!"

Sherlock squeezed his eyes shut, feeling tears of agony leak out. His entire body felt as though it were on fire, with the brightest ember centered in his abdomen. He was dying properly now, he was sure of it. And John was still there. Sherlock could feel his friend's hand still at his neck, and he rolled away, curling into himself. He didn't want to die alone like this, but he couldn't look at John's face while it happened. Not again. Not when it was real this time and not a magic trick.

I'm sorry, John.

From somewhere deep and hidden within himself, he heard a familiar Irish voice. "Come on, Sherlock," Moriarty called softly. "Just die, why can't you? One little push, and off you pop."

Sherlock clenched his eyes because god, Moriarty might actually be right. He was so tired, so tired of fighting. He could just let go, stop all this, it could be over, he could rest for once…

"Don't you dare."

Sherlock squinted through the sweat and tears trickling down his face. Someone was standing in front of him now: a military boot almost at his nose. He looked up and saw…John. Not the John who had just been with him, the Good Doctor Watson who gently nursed him through the shock. This was someone else, a John he'd only seen bits of on occasion. This was someone younger, with military-short hair, and dressed in Multi-Terrain Pattern camouflage.

This was Captain Watson of the Fifth Northumberland Fusiliers.

And he was not happy.

"Get up, Holmes," he barked.

"I…can't," Sherlock choked. "Sorry, m'sorry, John…"

Captain Watson knelt down, looking Sherlock straight in the eye. "I didn't ask, soldier. I said to Get. Up. And I meant it."

Sherlock took a deep breath and struggled to sit, failing about halfway. He shook his head. It was impossible; the pain was too great. The light was starting to fade out.

Captain Watson, he noted, did not seem sympathetic. A person with a bullet wound wasn't exactly new territory for him, so Sherlock's plight was likely less than impressive. Also, the Captain himself hadn't been shot yet, so he was lacking the first-hand experience that made Doctor Watson gentler. He stood to full height now, towering over Sherlock, arms folded. "You're letting me down, soldier," he said darkly. "You know I'm in danger. So get on your feet."

Danger. John's in danger. Yes…Sherlock was beginning to remember now…

Sherlock slammed his fist on the ground, using the force to push himself up. Captain Watson didn't offer help, but watched approvingly.

"That's it, Holmes," he coached. "On your feet now."

Sherlock stood, finding the pain was more manageable the more he moved. Finally, he was at full height, but by then, Captain Watson was gone.

"Holmes!" Sherlock looked up and saw him standing by the staircase that led to the door: his exit out. "Come on, solider!"

God, so many steps. As elegant as the staircase looked, Sherlock absolutely understood the practicality of installing a lift somewhere in case this ever happened again. He gripped the banister and dragged himself up one flight, then another. Captain Watson always just ahead of him, just out of reach, beckoning him forward.

He was almost at the top now, but Sherlock was stumbling, the pain coming back full-force mixed with delirium at being so close to breaking free. He blinked and Captain Watson transformed, not into Doctor Watson from before, but John, just John, looking like he did every night they chased criminals through London.

Except this time he was surrounded by light. Illuminated, actually. Curious, because Sherlock had told John years ago that he was a conductor of light, bringing out the brilliance in others (namely, Sherlock).

Clearly he had been wrong. What light there was, John was the source.

"Come on, Sherlock," he called. "Just a few more steps. Take my hand!"

John was at the door, halfway out, his hand reaching down. Despite the pain, Sherlock took the last flight two stairs at a time, then lunged forward. He felt his best friend catch him, grip his hand, and pull him through the door and into the light.

Right at that moment, the information Sherlock had filed away from John's room returned. He remembered what he had to tell John, what was so very important, but he was being pulled forward now at such a great speed, opening his eyes to the light around him, and he found he only had time for one word:

"Mary."

End note: Thank you for reading! I appreciate any feedback, as always