A.N. - Thanks to the lovely reviews I got for my last one-shot, I've decided to attempt a multi-chapter story, though it probably won't be a long one. The inspiration for this came from the preview for next Thursday's episode, and I decided to add a bit of Halloween fun to it. Enjoy! Warning: SPOILERS for the next episode (though the timeline might be off) and a Sheldon/Penny pairing; those who want the canon pairings need not read.

The Catalyst

Penny strolled down the mall, glancing at the store fronts to see whether she needed to go in or not. She'd gotten off from an early shift at the Cheesecake Factory, but rather than feeling tired, she had had an urge to do some shopping. She felt she deserved it, for she'd been working hard for a month straight, had paid all the bills herself, hadn't sipped one ounce of alcohol, and she hadn't splurged the remaining money on shoes. She'd been going to Sheldon and Leonard's less frequently as well, and she felt guilty for not talking to Sheldon about anything much lately. She knew that Leonard had probably been a pain in the ass to deal with after their third, and definitely final, breakup, but there was nothing Penny could do about it except to let Leonard move on. She had done the math in her head, too. Right about now, Leonard would feel the need to find a woman willing enough to go to bed with him so that he could forget about her and satisfy his desires at the same time. Raj had called her every other day to keep her updated on what was going on, but Penny found she hardly listened, unless it had something to do with Sheldon. Right then, her phone rang. It was Raj and Penny smirked, wondering if she should ask Sheldon about the possibility of mind reading over distances.

"Hey Raj, what's up?"

"Penny I've done something horrible and now I think I've broken Sheldon!"

"Woah there, Raj, what happened? Start from the beginning and go slower."

She could hear him sigh in frustration as he said, "This last week, Sheldon and Amy got into a fight over Indiana Jones. Amy was still upset last night, but you were working so she came over to my place to vent. Well, one thing led to another and we ended up having sex!"

"What?!" Penny dropped the soda she had been holding, it's contents spilling all over the floor but she could care less. Shock was flooding her system. "Holy crap on a cracker!"

"I know! The worst part is that we actually like each other and we don't want it to be a one time thing. So Amy and I decided to go over and tell Sheldon ourselves, because we didn't feel right about sneaking behind his back."

"Oh my God, is Sheldon alright?" Panic began to infuse Penny then, and she realized that she was already almost back to her car.

"We don't know. When we told him that we wanted to pursue a relationship together, he just looked at us without saying a word, then turned around and walked into his bedroom and closed the door. We knocked but he didn't respond. Penny you have to come and help, you're the only one who can!"

"I'm already on my way!" Penny raced home, praying that she didn't get stopped for speeding. She practically flew up the stairs and opened the door to 4A without preamble. "How is he?" she asked, noting that while Raj and Amy both looked concerned, they were also holding hands.

Both Raj and Amy leaped up from the couch, Amy hustling over to Penny. "Oh Bestie, he's still in there and hasn't made a sound. I fudged up bad."

Penny grasped her friend's shoulders and said, "Look, the way this happened was shitty, but I'm going to try to salvage it. I enjoy being your friend and I want to keep it that way. Let me go in there and try to talk to him, alright?" Amy merely nodded, tears slowly spilling down her cheeks. Raj whispered a thank you as she strode towards Sheldon's bedroom. Biting her lip, she knocked on his door. "Sheldon, sweetie? Are you okay in there?" Nothing. She tried again, but after about a minute she muttered to herself, "Strikes be damned, I'm going in there!" She opened the door, only to find that Sheldon was sitting on his bed, his chin resting on his hand, apparently lost in thought. "Sheldon?"

His eyes snapped out of his inner thoughts, coming to focus on her. "Oh, hello Penny. No one's allowed in my room, you know that."

"I tried knocking, sweetie, but you didn't answer."

"Oh, I apologize, I must not have heard you."

"Yeah, you did seem to be off in your own little world there." She hesitated then asked, "Are you alright? I mean, Raj and Amy are really concerned about you, and so am I."

"Are they? From what they told me just minutes ago, they certainly weren't concerned about my well-being last night."

"They feel just awful about how it happened, but they wanted to be honest with you. Surely that counts for something, right?" Penny had slowly made her way to his side, sitting down next to him and draping an arm around his back. He seemed not to notice her contact and that worried her a bit.

He sighed, replying, "Yes, that counts for something. Penny, can I be frank with you?"

"Of course, sweetie, you can tell me anything."

"Is it wrong that I feel relieved about the fact that Amy and I are no longer pair bonded?"

"No, absolutely not. Sheldon, no one can tell you how to feel, and if things weren't working between you guys romantically, then there's nothing that could have been done about it."

"I thought that due to our similar thought patterns that we'd be able to cultivate something beyond friendship, but while I care for her as a good friend, I don't feel the urge to become intimate with her physically."

"Well, you were considering it at one point. That was a big step for you. Sometimes, Sheldon, relationships happen to help you grow and learn. Being physical with someone doesn't mean that you had to give up who you essentially are, and I think that being with Amy showed you that."

"True, my work did not unduly suffer. I also enjoyed the look on Kripke's face when he found out I had a girlfriend."

Penny let out a laugh, to which Sheldon smiled at her in return. "Do you think you can face your friends now?"

"Of course I can, I'm not Leonard." The words stung, though Penny knew that he didn't mean them to. He must have sensed that he'd said the wrong thing, for as he stood up, he squeezed her hand. He went to the door, oblivious to the fact that she was frozen in shock, still sitting on the bed. Her skin tingled from where he'd touched her and she marveled at how soft, yet firm, his grip had been. She felt her cheeks begin to burn and she looked at him in awe, a myriad of emotions running through her. Crap, not this again, was her immediate thought. She generally tried to keep things platonic between her and her crazy friend, because really, there was no point in having any other types of thoughts regarding him. However, there had been times, such as when he'd challenged her to play panty piƱata, or the time when she'd pinned him down during their wrestling game, or any time they hugged, that she felt those familiar, intense, sensations which indicated she felt more for the tall nerd than just mere friendship.

"Are you coming or not?" And though his words were said in an innocent manner, Penny couldn't help the the innuendo forming in her brain, and her blush deepened.

He didn't seem to notice, however, so she forced herself to snap out of it, jumping up and saying, in a tad higher voice than normal, "Yeah, of course."

Sheldon turned away from her, about to open the door, when something in his brain told him to stop and think. For the first time, something beyond physics and science fiction was filtering into his mind, as his eidetic memory showed him the red coloring on Penny's cheeks, and he found that he thought she looked rather adorable when she blushed. "Fascinating," he murmured to himself, cataloging the information for future reference as he finally strode out into the hall.