John Watson was lounging on the couch, checking his email, when Sherlock Holmes came home (from whatever expedition he'd been on that afternoon) with a rare smile on his face. Sherlock threw his black trench coat into the kitchen and exclaimed, "John! You know how you're always trying to get me to go to a bar with you? To loosen up? Though I don't see why I'd ever need it. To loosen up implies that I'm too tightly wound, but I'm not all worked up, how am I supposed to function? So I still don't see why—"
"Sherlock!" John interrupted, "Get to the point."
"Ah. Well, I was riding home in the cab today, after having tracked down and put that scoundrel, Millers, in jail, I saw a bar that looks like it could be fun. IT HAS NO ROOF, JOHN! Can you imagine that? No roof! Well, I figured I would finally give your suggestion a go, and you and I are going to the bar! So get your coat!" Sherlock threw John's coat at him, and the black jacket landed on his head, blacking out the room for an instant.
When he pulled the coat off his head, Sherlock had already pulled his back on and was yanking John to his feet. "Ok, ok, Sherlock! Give me a second."
"No, John. Now!" And Sherlock pulled his flat mate out the door.
After a short cab ride through the London streets, Sherlock Holmes stood in front of a building, his arms spread-eagled in excitement. The structure behind him had a large, neon pink sign with the glowing words: 'Topless Bar' broadcast into the night as a redhead ducked into the building behind them. John tried his hardest not to laugh and Sherlock said, "See? I told you it looked fun!"
John said through his giggles, "No, Sherlock. I don't think you—" He paused as he considered whether or not to tell his friend about his mistake. He decided against it. "You know, you're right. But, I'm feeling a little wiped out. So, why don't you go on ahead, and I'll catch up with you back at the flat. You can tell me what it was like."
"But John, the sign says drinks on the first floor, and entertainment on the second. I bet they have a jazz band. That'd be classy. Can you imagine listening to a jazz band under the stars in a ROOFLESS BAR?!"
John tried again not to laugh, but rather walked up to his friend and put a stash of money in his palm. "Tell you what: the first drink is on me. And trust me; you're going to need it." He smiled at his joke.
Sherlock eyed him suspiciously. "Do you know something I don't?"
John just shrugged. "Doesn't that drive you nuts? Maybe you should figure it out." Then John climbed back into the cab and told the cabbie to take him home.
On his way back, John picked up his phone and texted:

Mycroft,
Did you not teach Sherlock ANYTHING growing up?
-JW,

A few minutes later, he got a response:

Not really. Why? What's he done now?
-MH

Well, he's at a topless bar because he thought it was a bar without a roof.
-JW

….Please tell me how that turns out. That's funny.
-MH

I will. And it is.
-JH

*

Sherlock didn't quite realize his mistake at first. He was unsettled when he walked in but he shook it off when he walked to the bar. He ordered a rum and coke with John's money, heading straight for the stairs.
Still, as he climbed the stairs, he couldn't shake the feeling that something was wrong.
He thought he realized the problem when he saw the roof. Sherlock was insanely disappointed.
Then he saw the women.
Sherlock abruptly about-faced. Now he understood the shirtless men downstairs.
The room began to swim and he briefly wondered if something had been slipped into his drink, before he remembered that he hadn't had even a sip.
Sherlock took one step back towards the stairs before slender arms wrapped around him.
"This is a topless bar, Sherlock. Let's get that shirt off you." He turned to face the somewhat familiar voice, finding a redhead in "proper" clubbing clothes. "Thanks for making it so much easier, dear," she purred.
His coat and scarf fell to the floor as he said not a word, staring at her face.
She slowly pulled his shirt un-tucked and started to unbutton it, beginning at the bottom. "Why, Sherlock, don't you remember me?"
He did, in fact, remember her. But the room around them did not lend itself to happy reunions. He had finally realized the strangeness. There was a large, subtle shift away from their side of the room, but it left behind a figure that appeared vaguely famous.
Before Sherlock could spring into action, the woman reached up and unbuttoned the very last one resting right as his neck with her teeth, letting out an all-too familiar sigh.
He looked down at her as she pulled the shirt off, wearing a look far too proud of herself. "You do remember Edith Williams, your old neighbor."
Sherlock ignored her lie and just as he opened his mouth to explain the danger they were in, there came a click.
Both turned sharply towards the sound the same second Sherlock wrapped his arms around the woman and pulled her to the ground.
Then the wall exploded.