He didn't know what possessed him to do it. There was, in stark and terrible contrast to his usual method, no thought process that had occurred. There must have been a decisive moment, but it had come and gone too quickly for him to process and, as such, he was on his feet with his lips pressed against Molly Hooper's before his brain had even managed to realize he'd been gripped with the compulsion to kiss her in the first place.
Now, he was left scrambling, his eyes wide open and staring into her equally shocked ones. His lips, following their initial malfunction in which they'd gently caressed hers for several seconds without his brain's permission, were still. His breath came in slow, shaky puffs against her face, and his hands loosely and lamely clasped her face between them.
He was so lost that it was, understandably, she who pulled back first, their mouths making only the faintest smacking sound that was distinctive to the end of a kiss as she did. He straightened as she took a couple of steps back, pulling her lips inward as though tasting them to make sure she hadn't been hallucinating.
He wished it had been a hallucination.
She took a breath and lifted her chin.
"Sorry," he cut her off, shoving his hands in his pockets so that she wouldn't see the way they were shaking, "Don't know what happened, there."
"Um...no," she agreed, her voice trembling as noticeably as his hands were, "Very...very unexpected, actually."
"Yes, it was, wasn't it?" he replied, forcing a lightness into his tone that he most certainly didn't feel, "Must have been the fumes."
"The pot on the stove," he clarified, gesturing vaguely behind him in the direction of said pot, "Experiment. Had to boil some potassium nitrate."
She frowned slightly, her eyes darting between himself and the pot.
"I thought it was pasta."
"Nope, KNO3. Odorless, so..."
He trailed off somewhat unconvincingly, and she persisted in a quiet voice,
"I thought you said we'd be working on something to do with pericardial fluids and that you were slapping something together for dinner."
"That was before I got the idea for the...thing. With the KNO3. Figured we could order takeout."
She narrowed her eyes once more at the pot before taking a deep breath and refocusing her attention on him.
"Shouldn't be harmful, KNO3. At least, not in theory. So...I'm not sure about fumes...?"
Sherlock raised his brows at her, thinking desperately. He was well aware that the human body is perfectly capable of handling inhaled nitrates, but he wasn't prepared for any of this and couldn't come up with any other explanation under duress.
Plus, he thought with a very disconcerting swell in his chest, he wasn't just dealing with any idiot. He was dealing with Molly, and she too was a scientist. A brilliant one, if he was honest.
"Not normal KNO3. This is modified, however. I modified it."
"It's complicated. Chinese? Italian?"
She set her jaw as he shoved his hands in his pockets once again and scanned his face. He held his breath as he tried his best to remain passive and unreadable when all he wanted to do was shove her out the door and be alone with his mutinous brain to think things over.
Or delete the whole evening. He hadn't decided.
Molly, being who she was when it came to him, sensed this and gave him a stiff smile.
"Actually, I...maybe there are some fumes floating around in the air. I suddenly feel a bit lightheaded...I mean, you know. Um...ill."
"Ah," he said, pressing his lips into a line of regret that was only half faked, "I see. Well, if you don't feel well, perhaps you should lie down."
"At home," he elaborated flatly, if too quickly.
"Right, yeah," she said, her voice breathy and rattled, "Maybe that would be good."
She made her way to the stairs of her own accord and began to hurry down them. Sherlock suddenly found that despite the fact that she was doing exactly what he'd wanted her to do by leaving, he was feeling conflicted about it. His body once again betraying him, he heard his own voice calling her back.
He heard her stop on the lower flight of stairs and then come back up a couple of steps so that she could peer around the banister at him.
He stared for a few seconds, completely lost for words. Why the hell had he called her back? Swallowing under her expectant gaze, he said inanely,
"I'll be at the lab tomorrow."
Wincing at his own stupidity, he was about to turn around and retreat back into his flat when she replied,
"I'll be there too."
"Good!" he said, too loudly before repeating in a more modulated tone of voice, "Good. We can start working on the pericardial fluid then."
"Right," she murmured, a small smile playing about her face as she went the rest of the way down the stairs.
The moment he heard the front door close behind her, he spun around and went to the stove. Grabbing the pot by the handles, he flipped it over and dumped the entire load of linguine that had been cooking into the sink. He stood there staring at it for a few seconds, then rubbed a hand over his face and turned toward his bedroom.
Only instead of the sight of his empty kitchen, he was confronted with the flushed and nervous face of Molly Hooper. Freezing, he stood there, startled into silence. She didn't say anything at first either – she was winded, as though she'd just run back down the block and up the stairs.
He swallowed, hard, and asked in a tight voice, "What are you doing back here?"
She shrugged and pointed at the kitchen chair, which still had her hideous striped bag slung across it. Their eyes met again as she explained,
"Forgot my bag."
Finally, after what seemed like an eternity, she glanced at the sink and smiled shyly.
"So...did you modify the KNO3 with linguine, then?"
The awkwardness was excruciating. Clearing his throat and looking down at his shoes, he said in a low voice,
He glanced back up at her. He thought he could see a bit of hope mingled with the humor there, but he wasn't sure. How could he be sure of anything when his brain was working against him? He cursed himself and went on,
"I should really apologize for kissing you. It seems to be one of the many unfortunate side effects of having to fake a relationship with Janine."
"Side effects?" she repeated, looking crestfallen.
"Yes...frequent kissing was vital to the deception."
She nodded rigidly. "Right. Of course."
"And it seems that after doing it so casually for months, it's hard to break the habit."
As he spoke, she reached out and grabbed her bag, and by the time he was finishing his sentence, she was backing out of the door again.
Perplexingly, he found that as he capped off his apology, he was stepping towards her as she backed away.
"I didn't think before I did it. It was just instinct."
"Yes. I apologize if it made you uncomfortable."
"It's okay," she said, giving him a fake smile, "It didn't."
"No...well, I mean..."
"Excellent. Good," he interrupted, smiling back at her.
A pause, and then she said, "Well...see you tomorrow."
She'd barely gotten to the top of the stairs before he was reaching out and grabbing her arm to stop her.
She turned to face him and her eyes widened as she realized how close he was standing. His own heart felt as though it was going to beat out of his chest as he looked down at her, his body vibrating with a tense anticipation as he considered that he might be about to completely ruin a relationship he valued very, very much.
"Yes?" she prompted softly when he didn't speak.
He drew a breath and asked, his voice hushed, "I rather liked it. The kissing."
"You did?" she breathed, and his own voice was raspy as he replied,
"Yes. To be perfectly specific, I meant I rather liked kissing you."
"I was hoping you meant that, yeah."
A long pause in which neither spoke nor did they look away from each other. Finally, he asked,
"May I kiss you goodnight?"
Her lips curved up in a smile, and Sherlock didn't wait for any further permission before his head descended to capture her lips again in a tentative, thoroughly unambiguous and completely premeditated kiss. The moment her shock passed and she began to respond, he snaked his arms around her waist and pulled her to him.