On the day of John Watson's wedding, it rained. It was not a light shower, no. It poured. What was that old wives' tale? John thought as he stood at the foot of the altar waiting for his bride to appear. Right. If it rains on your wedding the first seven years of marriage are supposed to be blissful.

Then, the pianist struck up the processional—Pachelbel's Canon in D.

John wished he could say that his breath caught in his throat when he saw Mary walking down the aisle, but he was distracted. Where was Sherlock? He should be there, standing with him as his best man. But he had been acting strange…well, stranger since he broke the news of his engagement. He had become more withdrawn than normal, and John, for the life of him, could not figure out why. In the week leading up to the wedding, Sherlock had gone so far as to ignore John.

Mary had reached the altar and her father placed her hand in John's, kissing her cheek before returning to his pew. She smiled happily at him, and for some reason, he thought she looked several times happier than he felt.

The music stopped, and the priest began the ceremony. "We are gathered here today in the presence of God to witness the union of John Watson and Mary Morstan. If anyone here objects to this union, let him speak now or forever hold his peace."

The church was silent.

The priest turned to John and intoned, "Do you, John Hamish Watson, take this woman, Mary Morstan, to be your lawfully-wedded wife, in good times and bad, for richer, for poorer, in sickness and in health, as long as you both shall live?"

John looked at the priest before turning to the woman before him. "I d—"

Suddenly, the doors at the rear of the church burst open. Sherlock stood in the entryway, clad in his customary coat, breathing slightly labored, as if he had run a great distance. He was soaked through to the skin and droplets of rain fell from his curls onto his face.

"John! Wait! There's something you must know!"

John looked at him, his facial expression a mixture of concern and annoyance. "Sherlock, what in God's name-"

Sherlock strode purposefully down the aisle. "John, you can't do this."

John ground his teeth. "Sherlock, for once in your life, would you stop being so selfish? Mary and I are getting married. You're interrupting it right now, as a matter of fact! Can't you just hold your tongue for five minutes and stand up here next to me as my best man like I wanted?"

Sherlock's lips pursed as his eyes darted about the room. "I can't... I get this feeling inside... DAMN THESE PEDESTRIAN EMOTIONS." He kicked at some flower arrangements for emphasis. "How can you just stand there in that silly tux, holding her hand, and ready to bind yourself to a lifetime of dull? Dull, John! Boring."

"Again with the boring," John muttered.

"How can you do this? What about our partnership? Our flat? Are you just going to give that up?" Sherlock shouted.

"Because!" John shouted right back. He took a deep breath to calm himself down. "Because, Sherlock, it was time for me to grow up. I met a nice girl. That's what people do. They grow up, and they allow their friends to grow up."

Sherlock started pacing. "This has nothing to do with growing up!"

John folded his arms. "What then? What has this got to do with?"

Sherlock froze. Slowly, he turned to face John. His lips twitched in an effort to say something he wasn't sure he could bring himself to. He closed his eyes, resigning himself. When he opened them again, his icy blue eyes bored into the doctor's, expressing his feelings in ways he had so much trouble articulating.

"I love you."

Sherlock spun on his heel and exited the church before John and the rest of the stunned congregation recovered from their shock.

A/N: Got this idea from a post on Tumblr regarding a rumor about the final moments of the Series 3 finale. I might do one more chapter with John and Sherlock talking it out if there's sufficient demand for it.

Constructive criticism welcome!

Disclaimer: Everything belongs to Steven Moffat and Mark Gatiss.