Sherlock's POV

When Sherlock heard the news of John and Mary's engagement, from Mycroft of all people, he'd been laying prostrate in his bed, trying not to suffocate with his face pressed against the mattress, buried in the pristine white sheets. The last of his withdrawal symptoms had come and gone a while ago, but he still had cravings and he was still miserable. His mind felt as if it were tearing itself to pieces, and he now had nothing to appease it. He'd known rehab wouldn't be easy, but he was pushing through it, for John's sake. 

John. 

He immediately pushed himself up and narrowed his eyes at his brother, who was sitting in a chair beside his bed.

"What do you mean he's getting married?" he snarled. Mycroft just sighed and rolled his eyes.

"Sherlock, I'm certain you know what the word marriage implies." Sherlock glared fiercely at his brother and made to stand from the bed. Mycroft raised a hand to still him, and he remained seated despite his defiant nature. "Trust me Sherlock, this is for the best."

"What do you mean best? I'm miserable here!"

"But you're clean." Sherlock groaned and rolled his eyes.

"Yes, yes, we can all celebrate later. As for now, I need to get back to London."

"Sherlock you can't just leave-"

"I checked myself in here, I can check myself out!"

"You're being irrational. Letting your emotions get the better of you." Sherlock gritted his teeth, resisting the urge to reach out and deck his brother. Ever since Mycroft had found out that his little brother actually had feelings and had managed to fall in love with his only friend, he'd never given him the chance to forget it. Mycroft wielded Sherlock's feelings over him like he believed being heartless  somehow made him superior. Sherlock could tell by the look on his face that was exactly what he was thinking. He took in a deep breath to calm himself down, and placed his hands in his lap, staring down at them as he counted to ten.

"I need to see John,"  he finally said once he trusted himself to keep his voice level under control. He heard Mycroft shift in his seat, and heard the heavy sigh he gave before speaking.

"I would advise you not to return to him."

"Why not?"

"He's currently in mourning." Sherlock felt a pang of sympathy in his chest for John. Only once had Sherlock truly ever been in mourning, and though it had been long ago he still felt the pain as if it were a fresh memory.

"I can help comfort him." Mycroft sighed and let his chin fall down to his chest. He sighed heavily, as if about to admit something terrible. Mycroft then looked up, and when Sherlock saw the infinitesimal hint of guilt in his eyes he felt his stomach drop.

"Sherlock, he's mourning you."

"Why on Earth would he be doing that? I'm not dead!"

"He thinks you are."

"Well why-"

"You disappeared, Sherlock! No one heard from you for over a month. Apparently John got worried and went to Scotland Yard, and then nearly every police force in the United Kingdom had a search party looking for you." Sherlock sat and listened to Mycroft tell him the tragic tale of what had happened, and when he was finished Sherlock sat in a stunned silence for several moments.

"Why didn't you say something? You knew where I was!" 

"Trust me, Sherlock-"

"You lost my trust the moment you identified that body as mine, knowing good and well it was not me." Sherlock flopped back onto his back and stared up at the ceiling, a crease forming between his brows. "Anyway, I told John where I was going."

"Are you sure about that? He seemed pretty convinced you had left his life completely."

"But, I sent him a letter. I specifically told Jim to give him my letter to John Watson."

"Jim?" Sherlock sighed heavily and nodded his head.

"Yes, there was this guy I'd met through Molly, who worked in IT. He said he knew John, so I told him to give John a letter for me. This was about a week after we'd had that argument. The day before I hopped on a plane to come here." He groaned and pressed the heels of his hands against his eyes. "I told him everything in that letter." Mycroft raised an eyebrow at Sherlock.

"Everything?" Sherlock sighed and nodded his head.

"Everything. I poured my heart out on that paper like a teenage girl."

"You're not serious."

'Of course not." Sherlock rolled his eyes and sighed for dramatic affect. "I did tell him that I would honour his last wish for me.. I told him I would get clean, and when I was I would come back to him." Sherlock shut his eyes tightly and covered his face with his hands. "I don't understand how this went so wrong."

"Perhaps Mr. Watson never received the letter." Sherlock groaned  as the realization finally dawning on him. He mentally kicked himself for not figuring it out sooner, before Mycroft had. He felt his heart rate increasing and he practically growled as he sat back up.

"I swear, I am going back to London this very instant and I am going to murder that Jim."

"I don't think that will be possible, brother dear." Sherlock whirled his head around to glare at Mycroft, who was staring down at his phone.

"Why not?"

"There is no person working in IT as St. Bart's named Jim, or anything that might be shortened to that. There hasn't been for years."

"Well that's just great." Mycroft began tapping away furiously on his phone. "I assume you'll be getting right on that situation."

"I won't personally, but I will have some people look into it for you." Sherlock rolled his eyes, but thanked his brother. He didn't really need a stranger out there with information about his drug habits and affair with John. If anything, he didn't want to ruin John's life if word were to get out about them. Especially if he actually did want to stay with Mary, though Sherlock was beginning to entertain the idea that John had not chosen Mary over him, but rather stayed with her thinking that Sherlock was no longer an option. One could only hope.

Suddenly his head snapped up and he turned to Mycroft.

"When's the wedding?"

"Two days." Sherlock's jaw dropped and he stared at Mycroft for several seconds. Then Sherlock stood up from his bed and stalked over to the wardrobe in his room. He threw it open and grabbed the first shirt and trousers he saw. He threw them onto his bed, not caring that they would get slightly wrinkled, and turned to Mycroft.

"Get out."

"Sherlock what are you-" Sherlock rolled his eyes and shrugged out of the dressing gown he'd been wearing. "Sherlock!" He ignored his brother and continued to undress. When he made to remove his shirt Mycroft stood from his seat and went to the door. "I'll be right outside."

Sherlock ignored him and continued changing. Several minutes later he was smoothing down his shirt and trying to get a decent look at his outfit without the use of a mirror. There was a knock at the door before it opened and Mycroft stuck his head inside.

"Good, you're decent." Sherlock glared at him, but he was unfazed. "Sherlock, I can see what it is you want to do, but I must advise you against it."

"Oh Mycroft, when have I ever listened to your advice?"

"Sherlock, you're in a much better place here, without him."

"And who are you to decide that for me?" Sherlock grabbed a pair of shoes and hastily put them on. Mycroft groaned and gave him the look he'd given often when they were younger. His 'I'm-your-older-brother-so-I-automatically-know-what's-best look. It was a look Sherlock absolutely despised, and now it made his skin crawl.

"Sherlock, this isn't-"

"Look, I've been here for months now. I'm pretty sure I'm okay to leave."

"You can't-"

"I checked myself in here, I can damn well check myself out."

"Sherlock your case was quite severe. Prolonged use, and heavy doses each time. You're not okay." Sherlock reached deep inside the wardrobe in his room and pulled out the Belstaff coat he hadn't worn in over a month, sighing as he slid into the familiar garment.

"Yeah, well, I'll be even less okay if I don't get the chance to see John before he gets married." Sherlock avoided eye contact with his brother as he went past him to the door. "I'll be back to pick up my things later."

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John's POV

John stood before the mirror and took a look at himself. His eyes were drooping, his worry lines had grown more prominent, and the corners of his mouth were turned perpetually downward. He looked absolutely miserable, and felt miserable as well.

A door opened behind him and he schooled his features into a mask of contentment, possibly even joy, as he turned around. Mike Stamford was poking his head inside, smiling at him.

"Hello there Mister Groom." John motioned for him to come inside, a genuine smile coming onto his face

"Mike! What are you doing here?"

"What do you think?" He asked, holding out his arms so John could appreciate his suit. "Just because we haven't talked in forever you think I'd want to miss out on the happiest day of your life?" John barked out a laugh to cover up the sharp pain Mike's words had evoked in his chest, and the two shared a friendly hug.

"I'm really glad you could make it."

"Wouldn't miss it for the world."

They chatted for several minutes before Mike left to go find a seat in the church. John, alone once again, allowed his facade to melt away and turned back towards the mirror. Seeing Mike had been great, but now all he could think about was that night when they'd been called to that hotel. The night when he'd met Sherlock Holmes for the second time. He remembered Sherlock explaining the case to him later on, when they had been living together.

It hadn't been a Red Rum case, as Sergeant Donovan had suspected. John laughed when he thought about the way Sherlock's face had scrunched up when he'd mentioned the woman. He remembered the way his stomach had twisted itself into a knot as Sherlock told a tragic story of a love gone wrong, and how husband and wife had met their tragic ends.

The husband, unhappy with the state of their marriage, had gone out seeking a new spark with someone else, and the wife had caught on. She found out about their plans to spend the night at a hotel, and had met them there. What started out as a domestic altercation had become far worse when the wife had brandished a gun and was attacked by her husband's lover with a knife she kept concealed on her person. During the tussle the gun fired, killing the girlfriend, and the husband, devastated by the death of his girlfriend, took the gun from his wife and killed himself. The wife had somehow managed to hide the girlfriend's body in the closet before she collapsed onto the floor, the blood loss finally having caught up with her once the adrenaline wore off.

Oh, love, what a terrible thing. John could surely attest to that.

"John?" He turned away from the mirror to see Greg Lestrade standing at the door, a concerned look on his face. "Are you alright?"

"Yeah, I'm fine." John sniffed, and glanced at his reflection, and saw that his eyes were red rimmed and watery. Great, he was going to look fantastic in the wedding pictures. 

Lestrade looked skeptical, but apparently decided not to say anything, and instead informed John that the wedding would be starting soon, and it would be kind of difficult to have a wedding without the groom.

"Right, I'll be right there." Lestrade nodded and went out the room, and John took a moment to steel himself. He sucked in a breath, then reached down and picked up the folded piece of paper that had been sitting before him, leaning against the mirror. It was a program from Sherlock's funeral that he'd kept all this time. There was a picture of Sherlock on the front. That was why he'd kept it; He had no other pictures of Sherlock. He hugged the paper tight to his chest and closed his eyes, sighing.

If only things had been different. If only he hadn't been so stupid, if only he'd told Mary the truth. If only, if only...

It was too late now for regret. The ball had started rolling and it would take a miracle to stop it. John placed the paper down in front of the mirror and let out a shaky breath.

"Oh Sherlock," he said in a hoarse whisper, "I wish she was you."

___________________________________________________________

Sherlock's POV

 Sherlock had always hated flying. It was the most tedious method of travel, consisting of nothing other than sky and clouds and a dreadful in-flight movie. This particular flight was made worse by the fact that Sherlock knew John was on the other side of it. At least, he hoped John was on the other side. He wasn't exactly sure what he'd be returning to in London. 

It had been only a day since he'd found out John was to be married, and it had been all Sherlock could think about for the past twenty-four hours. John, holding hands with Mary at the front of a church, with all of their friends and family gathered, some crying, others smiling, possibly even some drifting off to sleep depending on whether the service was dull or not.

Sherlock found himself picturing himself in Mary's place. He pictured himself sliding a ring onto John's finger as they stared lovingly into each other's eyes, and his heart ached. He wondered if he would ever have that for real, and hoped desperately that he would. 

The plane soon landed and from that moment on everything seemed to blur together in Sherlock's usually precise memory. He decided to blame the jet-lag. He had just flown from California to London, after all. 

He remembered hailing a taxi outside the airport, and telling the cabbie that the sooner he got them to the church the more money he'd get. He remembered getting caught in heavy traffic, caused by a terrible accident, and practically leaping from the car so he could run past it all, hailing another cab once he got to the outskirts of town.

Following the directions Mycroft had texted him, Sherlock made it to the church, though unfortunately the service had already started, and Sherlock found himself with his ear pressed against the church door, heart pounding as he waited for the priest to say the words that would warrant his entrance.

"Is there anyone here who believes that this couple should not be wed, speak now or-"

Sherlock didn't even wait for the priest to finish speaking. He calmly opened the door, and ignored the shocked looks on everyone's faces as he walked up the centre aisle, his eyes remaining locked with John's.

"I do."