"This isn't good," Sherlock muttered.

"Oh, I think it's lovely," Mary said, cutting into her molten cake.

Sherlock flicked his gaze towards her, frowning. "I wasn't talking about the food; I'm talking about the case. I think they're on to us."

"Maybe if you wouldn't act so suspicious," Mary muttered, looking back to her food.

Sherlock looked at her again. "Suspicious? How am I suspicious? I'm not being suspicious."

"Well, you're not eating, either, and this is an expensive restaurant. Who gets a reservation and doesn't eat?"

"You're eating," Sherlock retorted.

"You need to eat."

"I can't eat," Sherlock said, looking back around the restaurant.

"You mean you won't," Mary said.

"No, I mean I can't," Sherlock replied absently, subtly glancing towards their suspects from the corner of his eye.

"Why not?"

"I get nauseous when I eat on a case," Sherlock said. "My stomach doesn't handle digestion well when I'm otherwise occupied."

"Aw. That's cute. Sherlock Holmes gets nervous," Mary said cheerfully.

He looked back at her. "I am not nervous. I'm never nervous."

"You looked nervous when you told John you were still alive. And at my wedding," Mary said, glancing up again. "Your speech."

Sherlock scowled and looked away again.

The rest of dessert went as such until-

"Mary," Sherlock said sharply. "They're leaving."

She looked up. "Hm?"

"They're leaving." Sherlock placed the money on the table and stood, grabbed Mary's hand, and practically dragged her out of the dining area.

"Sherlock!"

"Shh."

"Mr and Mrs Holmes, let us retrieve your coats-" one of the staff started.

"Back in a moment," Sherlock said dismissively.

"Sherlock!" Mary protested again.

"Be quiet..." he muttered, eyes intent on his suspects - figures in the distance already.

Except, when he had converged on them enough to make out the features in their face and they looked directly at him, Sherlock did what he had to protect his façade.

So, he spun around to hide his face, drew Mary close, and pressed his lips against hers.

He'd never kissed anybody before, but the mechanics certainly couldn't be terribly difficult. Mary had tensed up considerably but, after Sherlock slid his hands down to her waist, pressing his fingers into her skin pointedly to tell her go with the flow, as such.

She kissed him back. It was very unlike anything that Sherlock had ever experienced. It wasn't entirely un... pleasant. Except that it was Mary and John was probably going to-

There was suddenly a sharp noise and pain exploded from his cheek. He reeled back from the force of the slap, looking at Mary with wide eyes.

"What... what are you doing?" he asked breathlessly, pressing his hand against his cheek and twisting around to look for the suspects. They'd gone, which was good, he supposed. At least they hadn't realised that Sherlock Holmes was on the case yet. "That hurt," he said, looking back at Mary.

"You kissed me!" Mary exclaimed.

Sherlock glanced around himself slightly, half expecting someone to pop out and say surprise! "... So?" he asked shortly.

"I'm married," she retorted.

"I know; I was there," Sherlock said, frowning. "But that doesn't explain-"

"You don't go around kissing your best friend's wife, Sherlock!"

Sherlock's frown deepened. "I didn't think you'd have a problem... Was it not satisfactory?"

"It was... it was fine. I prefer John. And you've been smoking," she accused.

Sherlock huffed. "Well, you taste like chocolate."

"That's better than sucking on a cigarette," Mary said.

Sherlock sighed and dropped his hand. "This is ridiculous. At least the suspects didn't totally catch on..."

Mary's laughter broke Sherlock out of his case disappointment; he looked back at her again with yet another frown. "What? Why are you laughing?"

"Your face," she laughed. "It's hilarious."

"You slapped me!"

"With good reason."

"Why are you laughing if you slapped me?!" Sherlock protested.

Mary chuckled and shook her head. "I keep forgetting that you know nothing about human nature. Or boundaries, apparently." She sighed. "Can we get our coats and go home? It's getting chilly."

Sherlock scowled and turned away. "I do not understand you."

Mary smiled, looping her arm with his. "Just don't try to kiss me and we'll be fine, Sherlock."

Sherlock huffed and shoved his hands in his pockets, although he didn't push her away.

Three months later

"Can you make molten lava cake?"

John glanced up. "What?"

"Lava cake. I don't know to make it," Mary said. "Sherlock said you can cook."

Sherlock gave a little 'hm' from his place at the counter, switching out the slides in his microscope.

"I don't know..."

"We'll have to look up a recipe," Mary said. "I had a lovely piece when Sherlock took me out on that case..."

Vague memories filtered back into Sherlock's mind and he licked his lips reflexively. "The chocolate was actually quite good," he muttered, more to himself.

"What was that?" John asked.

Sherlock paused. "... Nothing."

Mary glanced up. "Oh, I forgot to tell him. You didn't, Sherlock?"

Sherlock glanced away from his experiment slowly. "... You know, I think I'll go out," he said, standing abruptly.

John glanced up. "What?" He looked at Mary. "What didn't he tell me?"

Sherlock grabbed his coat, shoving his arms through the sleeves and swiping his scarf from the chair by the door.

"Sherlock kissed me that night," Mary said cheerfully, licking her thumb to turn the page in her book.

"What?"

Sherlock hurried down the stairs, buttoning his coat as he went.

"Well, to be fair, it was part of the undercover thing..."

There was a thump from upstairs and Sherlock winced slightly, fluidly jumping the last three stairs to get to the front door.

"Sherlock!"

Sherlock closed the door behind him, hurrying towards the street to hail a cab to somewhere where an angry John couldn't find him.

Just a little cracky piece that I wanted to write up before His Last Vow airs. I think it would be adorable if Sherlock and Mary went undercover like this and something happened... and then Mary had to hold John back to stop him from pulverising Sherlock. :p

I do not own Sherlock. Thank you!