*Previously on The Big Bang Theory:

"One, two, three, wrestle!"

"Mwa!" Sheldon exclaimed, laughing after he kissed Penny.

"I can't stop now, Penny. I need to have you." Sheldon barely spoke.

"The bedroom. Just take me." Penny whispered in desperation.

"Let's go."

"Sheldon! Guys! This isn't the game we're supposed to play!" Amy yelled hopelessly after the couple.

"What the hell are we gonna do, Leonard? We have to stop them!" Amy marched furiously back in the living room. Leonard remained passive, which surprised her. She thought he will be more persuasive to stop the madness.

"Well!?" Amy waived her hands in the air, looking at Leonard, perplexed. "Will you just let you lifetime goal end like this? With your girlfriend ending up in bed with your best friend!?"

"Calm down, will you?"

"Calm down, that's your suggestion!? Ugh, everything is going wrong! Why!?" Amy thought out loud. Leonard obviously won't offer her any help. It was up to her to think of a solution.

For starters, a kiss between Sheldon and Penny was never supposed to happen. She worked for two years, to train Penny out of Sheldon's mind. Trying to focus more of his attention to her, instead of Penny. All her plans were now in jeopardy.

"I worked so hard to make him mine. But that slut gives him one kiss and everything is shattered!"

"Hey! Amy, you can't make people you property. Why are you so obsessed with him anyway?"

"Why? I'll tell you why. He's the only chance I have to live a normal life with a boyfriend!"

"I'm sure there are other men out there for you."

Leonard offered a bit of his sympathy for her. He was always close friends with Amy. He knew exactly how she was feeling. Sheldon was an enigma for both of them on his own. When adding a 'Penny' variable into the equation, it suddenly became exponentially more complex for them to understand his behavior.

"Love isn't science or a computer program, Amy." Leonard tried to talk some sense into her.

"Wrong! I'm a neuroscientist, programming minds is what I do." Amy was still being sure of her methods. "No, my work is flawless, that..." She pointed towards the bedrooms. "That's just a bug. I'll wait them here and fix him, once and for all."

"Fix Sheldon? Again?"

"I'm no quitter. It will work. It must..." Amy insisted on Sheldon being her boyfriend.

An hour went by and still no sign of Sheldon and Penny. Leonard brought Amy a cup of cocoa to make her feel better. She was much more hurt by this betrayal than he was.

"You're still thinking about winning him back?"

"I am. I'm not about to throw away all of my progress on Sheldon. I will make him mine again." That was all Amy could think about. How to alter her plans and formulas to make Sheldon fall in love with her and forget Penny. "How come you're taking this thing so easily?"

"It's not the same between me and Penny, as it used to be." Leonard explained the mutual loss of interest. It happened before and it was happening again. This time for good. The chain of events in recent weeks made him to stop seeing Penny as his destined girlfriend, a wife and a mother of his children. There was too much friction and too little passion between them, to make it a stable long-term relationship. His biggest fear was having to divorce her, after creating a family together. He couldn't stand the thought of Penny ending as an alcoholic single mother. He'd rather end it now and let her find true happiness.

"If you need my further help with Penny, just say it." Her words and evil smile were off putting.

"No. No more tricks. I already said this to Sheldon once, no one is changing her, ok?"

"What do you mean, you said it to him?"

"Before you came into our lives, Sheldon once tried to correct Penny's behaviour by positive reinforcement. He gave her a piece of chocolate every time he considered her behaviour as good."

"He never gave me any chocolatte..." Amy was disappointed at this revelation. Sheldon never treated her as Penny. "So did you stop him?"

"Yeah, I forbid him to continue the experiment. Then he sprayed water into my face."

Leonard recalled the events from that evening, thinking about them from a new perspective. He was talking his thoughts out loud, staring into the distance. His typical thinking mode.

"She and I ended up having sex on her new bed, which I had to put together..." Then it hit him, Leonard only now realized why Penny put out that night. "Son of a bitch!"

"Looks like she trained you with some positive reinforcement as well." Amy chuckled at Leonards realization and winked at him.

He recalled all the other events in his relationship with his neighbour. Their beginnings. Was her love for him even real? Or was she just using him, because he could not say no to her? Only hours after they met, she already "asked" him to retrieve her TV back from her ex. All his fond memories were now tainted. Penny was drunk on a couple of occasions when she came onto him. On others, Leonard had to do something for her, before she showed her affection. After her breakup with Zach, she got drunk and used Leonard for rebound sex. These thoughts were the final nails getting hammered into place. Everything only confirmed he was right in his decision. Bury this ill-fated relationship and move on.

Sheldon and Penny finally peeked from the bedroom. Together, they walked into the living room to face their destiny and future. They didn't held hands, but Sheldon did follow Penny closely to the kitchen counter.

Amy was already prepared for the face-off in her usual angry mood. Earlier conversation calmed her a bit. But then she noticed how Penny was literally glowing, after a passionate coitus with her boyfriend, the same rage boiled up again. Penny was slightly embarrassed and blushed by the situation, scared by the anger on Amy's face. If this was a cartoon, puffs of steam would be blowing out of her ears.

Sheldon relieved the awkward silence by speaking first.

"Leonard, if it's in any consolation, I did won that game." Sheldon announced proudly, trying to lighten up the mood. Leonard looked at him from the couch.

"Can't say I'm surprised. I always knew there's something more beneath the surface with you two. Something much more than I could have with her." Both Sheldon and especially Penny were surprised at Leonard's calm and easy understanding of the situation. Like a huge lump rolling off her chest, Penny quickly felt easier.

"Sooo you're ok with us being together, then?" Penny had to double check with Leonard. It felt very strange and almost wrong. Leonard letting her go this easily, after years of doing everything he could to be with her. She did not know about his realizations earlier.

"Penny, waiting here for you and thinking about us, only confirmed my decision. I already moved on from us, on my own. Her name is Alex. Sheldon's assistant in the office. I wanted you to know about her, I would never cheat on you. But your little fling with Sheldon, just spared me a whole lot of drama and broken hearts. I… can't even be mad at you right now." Leonard smiled at her, happy that the breakup with Penny went so smoothly.

Penny didn't know how react to this revelation. She felt hurt over his rather emotionless revelation and a quick rebound. But she could not be angry at him, when she just did the same thing. On the other hand, she was relieved, that her relationship with Leonard was considered over, before she jumped into bed with Sheldon. It was a little grasp of comfort, knowing she didn't really cheat on him.

"I'm really happy for you, Leonard. I'm glad you found someone else. This thing between us, it would never work the way we both wanted to. Sex was the only thing keeping us together. You could never say no to me, but I need that in my life." Penny felt better for a moment, before Amy opened her mouth.

"So this is why you didn't say anything!" Amy broke the conversation. She was angry at Leonard for not stopping them earlier. Which made sense on the second thought about it. "Fine. Be with Alex, keep her away from my boyfriend." Amy spoke with unconstrained anger.

"Sheldon, you come with me and we'll discuss your actions!"

Amy wanted to grab Sheldon's arm, but he repelled her reach.

"I'm not leaving Penny for you. I had feelings for her since the day we met. I loved the way she appreciated my mind that day. Something which you never did. My feelings for her go far beyond what I feel for you."

Sheldon put his arm around Pennys waist and held her closer. Watching how mad Amy was turning after his denial.

"Amy..."

"Sheldon and I are a couple now, you'll just have to deal with it." Penny but it bluntly, lighting up the vapors of fury, gathered in Amy's mind.

The pain of losing Sheldon to Penny, of all the girls in California, it was too much for her to handle. Two years of planning and work, everything was utterly lost at this point.

Her shaky palm slowly reached towards her forehead, like she was trying to keep her head from exploding in anger. She fixed her glasses up a bit.

"That's an order, Sheldon! You're my boyfriend and you're not leaving me! How dare you disobey me! How dare you say your love for Penny! You're are the complete opposites! You don't belong with her, you belong with me! She's a drunk, a whore and a cheater! Stay away from her!"

A stream of rage, screeching and profanities burst out of her mouth in the loudest and most insulting voice possible. Like a person possessed, Amy poured all her fears and bottled up hate, dumping all onto Sheldon and Penny. This was her worst nightmare coming true.

Penny began to sob into Sheldon's shoulder, as Amy's anger and insults stabbed her, she held Sheldon tighter. Amy breathed heavily, fire lit up her darken eyes as she was catching her breath. Her face was red.

"So this is where we're at. You were lying and deceiving me this whole time! Even you, Leonard!" Amy now focused her rage at him. "We had a deal, remember!? I broke them apart, so you can have Penny and this is the thanks I get!? Two years of work, down the drain!" Amy waived her hands in anger, pacing around in the middle of the room.

"I thought you were my friend, Penny. But you're all just a bunch of cowards, liars and disloyal cheaters! Fucking around, breaking hearts, jumping from one bed to another!"

"Amy, I will not allow you to insult Penny any further..."

"Oh, fuck you, Sheldon! How can you be with this cheating whore instead of me!? You're a failure! You always were! Dumber than my lab monkeys. But still not as dumb as the blonde monkey!"

"We're not having this conversation any longer." Sheldon turned angry, pointed his finger at her.

"You're horrible people! Hurting each other's feelings, sleeping with one another, not a trace of humanity and dignity is left in you! You need me, Sheldon. You all need me! I'm the only one who can turn you into a normal human being. I achieved so much in my experiments! I know everything about you, I can save you! We can be so happy together, away from this world, working on science together. I licked all of your belongings in your office the other day, doesn't that mean anything to you?"

Amy settled her tone a bit. Which Penny took as an opportunity for a counter-attack. Sheldon was left appalled by Amy's disgusting revelation, but Penny remained focused enough to strike back.

"You torture animals for a living! You spread your smell all over our stuff, how dare you tell us how horrible we are!" Penny yelled through her tears. She was fed up with Amy's crazy behavior as well. She always knew what Amy was doing in her lab, but never had the courage to stand up to her. Penny always loved and cared for animals. Being a country girl, she always shared a bond with all sentient beings. She cared for animals, instead of torturing them and using them for experiments.

Amy settled down on the white single seater sofa to process all the anger and emotions, moving from anger phase to depression and realization. Penny's words brought her down.

"I never meant to hurt any of you." Amy lowered her head in despair. "All I ever wanted was to have a normal life, with my boyfriend and my bestie. But you were all deceiving me from the very beginning! Thinking of me as some kind of a joke. An alien in your cohesive group. You should all be executed for such treason. And for everything else you did to me."

Broken Amy now looked up at Penny. Sadness replaced anger.

"You never were my best friend, were you?"

Penny only nodded her head in denial.

"No. After I had to clean my whole apartment because of your insanity, not really."

Despite everything, Amy didn't shed a tear.

"And Sheldon was never my boyfriend. The one who could love me back on his own. Without drugs or tricks." Amy began to realize why her long-term plan would never work. She was never even close to being with him, no matter how hard she tried or what she did. She could never have what Penny had. The connection that propelled their relationship on its own. It was time for her to accept the defeat.

"This relationship... is over. I cannot carry on like this. Do what you want with one another. I don't want to be part of this charade any longer."

Amy raised up and stormed out of the apartment in a hurry.

The silence settled after the door slam, Penny embraced Sheldon again. He held her tight.

"Are you ok, sweetie?"

"I am. I'm glad that's behind us now."

They both sat on the couch, in their usual spots. Penny leaned in onto Sheldon chest, just wanting to be alone with him and his thoughts. To console her, heal her emotional wounds. Leonard gave them space on the couch. He got up and walked towards the door, without saying anything.

"Leonard?" Penny turned to him. The noise of the door handle acted like a bell to her. Leonard was about to leave, but she had thoughts for him. She couldn't let him go, not without being honest and open. Leonard didn't say anything, he just stopped and looked at her.

"I know I didn't always treat you fairly. Can we… at least try to remain friends?" She looked at him, pleading.

"I will always remain friends with you, Penny." Leonard smiled back at her.

"Oh, I'm so glad we're ok." She looked at him, then at Sheldon. "I love you guys. You are everything I needed in my life."

Leonard couldn't resist the emotions and had to come back to them for a group hug.

"And you are everything what we needed." Sheldon thanked her again. "You changed us for the better."

Over the years, they all became dependent on one another. Much more than they wanted to admit. Especially Sheldon. He always wanted to remain self-sufficient and independent. Living his life separated and void of human relationships and bonds. Never believing he will meet a person like Penny. The only one he lowered his shields for.

Penny never thought she would become friends and lovers with people like Sheldon and Leonard. But she did, for which she would always remain grateful. She learned from them as much as they learned from her.

She gave Leonard the courage and self-confidence he lacked. Sheldon showed him a meaning of true friendship. He would always remain grateful to Sheldon for saving his life. Leonard knew Sheldon was a jerk when it came to petty problems, but he was always be there for him, when it really mattered. He could always count on Sheldon to help him with his work.

"Well, I'll see you guys later. I have plans with Alex tonight." Leonard broke the emotional moment.

"Leonard, she's still my assistant..."

"You have nothing to worry about, Sheldon. I'll bring her home by ten."

"Ah, perfect. You kids have fun."

Penny smiled and fell into Sheldon's embrace again. A glimpse of the future flashed through her mind.

A future which she was not concerned about. Everything made sense again. Everything clicked into place in upcoming days. Their lives were turning for the better. Bernadette, Howard and Raj all felt it in the air. They were not really surprised, when they first heard the news about the breakups and new couples forming. They all came over the next day on Sheldons and Pennys invitation. Leonard brought Alex to meet the rest of his friends. Their lives returned back on tracks, just like old times. Dinners, video games, paintball, science. Spending their lives with best friends and loved ones, without sacrificing their passions or hobbies.

The subject of Amy was never brought up again. Alex was very grateful for Bernadette and Penny's friendship. Happy for being with Leonard. Happy for the best friendships in her life. They all were. Sheldon's scientific mind remained fascinated by this butterfly effect. How an instant decision, one instant action to kiss Penny's lips that day, escalated to completely transforming all of their lives for the better.

THE END