"Slut."

Penny reeled. The word had been visceral; the blow almost physical in its effect. The rational part of her mind tried to throw a calming blanket over the fire of rage it had ignited.

He was hurt. He didn't mean it. He just wanted to make you feel as bad as he does.

All very good points, she thought, but realised she didn't give a fuck; Leonard Hofstadter was going to be getting a few painful home truths.

And then…then she was gonna have a little chat with Sheldon. Junior Rodeo style.

…

She didn't stop to knock at the door to 4A, just barrelled right on through.

"Leonard! Where the hell are you?"

She stopped suddenly at the sight before her. Leonard was stood inches from Sheldon, his face red as he ranted. Sheldon stood impassive; jaw set, arms folded, looking down at the shorter man.

She slammed the door behind her and they turned as one to face her.

She focussed on Leonard and something in her face must have tipped him off as to how the next few minutes were going to go, 'cause he suddenly seemed much less sure of himself. She walked towards him and felt a small twinge of satisfaction as he tried not to back away.

"You! You come into my bedroom, uninvited, and call me a slut?! How dare you!"

Sheldon whipped around to face Leonard. "You called her a what?"

Penny turned on Sheldon, eyes dark. "And you can stay the hell outta this, mister, because you and me are gonna be having some serious words later." He shut his mouth suddenly and looked pale. Leonard smirked, then stopped quickly when he realised Penny hadn't finished with him.

"I can't believe you, Leonard! Yes, I screwed up. I screwed up big. And I am really, really sorry. But you are not innocent in all of this and you can't keep pretending you are. You treat Sheldon horribly! Even I know his work is the most important thing in his life, and you ruined it for him and humiliated him in front of everyone. That is seriously outta line, Leonard, and you didn't even care... all you were bothered about was screwing me."

She took a breath, then continued, ignoring his stunned expression and gaping mouth. "Don't bother trying to deny it. Oh, and the 'poor me I'm so upset' thing? Yeah, more believable if you actually cared for me, and didn't just wanna get into my pants." She looked at his face as he started to protest, and carried on. "Oh, I have no doubt you think you care. But honestly Leonard, I'm not convinced. Remember when Alicia moved in and you basically dropped me for her? It was like you turned into Wolowitz or something! You may be smart, but as far as I can see, you've been treating me exactly the same as all the other jerks I've gone for. I just didn't see it before, cause I actually thought you were different, but after this? I still wanna be your friend, Leonard. But we should not be dating."

She sighed, her anger dissipating slightly, a hint of resignation entering her voice.

"Face it, Leonard. I didn't hurt you. I hurt your pride. And your stupid ego."

He looked like he was going to argue with her, but she turned, dismissing him. Instead, she focussed on Sheldon. He was looking at her uncertainly. He had showered and changed his clothes, she realised with a pang. Of course he had; he's Sheldon, her brain helpfully supplied. She shut her eyes briefly, then opened them once she had steeled herself to meet his gaze.

"Could we talk in private?" she asked curtly. Sheldon nodded, replied hesitantly; "Would my bedroom be sufficient?"

From the corner of her eye she saw Leonard open his mouth to protest and she whipped her head round, pointed at him. "Don't. You. Dare!" She gave him a glare that could shatter glass and he flopped onto the couch as if his strings had been cut.

"Yes, Sheldon, it would be sufficient. Come on." She glanced back at Leonard over her shoulder as they left. He appeared to be sulking.

She followed him into his bedroom, thought how different it felt this time. His betrayal was a lump in her belly.

He had changed the sheets, too. Despite her brains insistence, in her current state it just smacked of him trying to remove all trace of her.

She eyed him as he stood before her, his arms crossed as he waited expectantly. The thought occurred that he had filled out a bit since she had first met him; his sleeves were pushed up to reveal his forearms, which seemed bigger, and his t-shirts looked to fit better. If she wasn't so goddamn angry at him, she might have found it sexy.

She sighed, and shook her head slightly. Her voice came out as a near-whisper. "Sheldon. What the hell?"

He tilted his head at her. "Penny, I'm sorry but you're going to have to be more specific."

She exploded. "Specific, Sheldon?! Freaking specific?! You mean you don't even realise what you've done? Oh my God, how can you be so goddamn dense?" She made a frustrated noise, ran a hand through her hair. "You used me, Sheldon. You slept with me to get back at Leonard, then you humiliated me by telling him really personal stuff! Is that specific enough?"

He took a half step back as the intensity of her outburst took her into his personal space. He waited until he was sure she had finished before responding.

"Oh....well then. I'm sorry."

She looked at him, momentarily speechless. "You're 'sorry'? That's it?"

"Well, no. I'm sorry you appear to believe that I 'used' you. Certainly that wasn't my intention. At the time, I was merely following what presented as a biological imperative."

She looked at him, blankly. "What?"

He sighed, looked vaguely irritated at her failure to understand. "Penny, I slept with you because I felt attracted to you and because I wanted to. No other reason."

She felt the lump in her stomach ease a fraction. "Oh. Well, good."

"I can assure you, Leonard didn't enter my mind until at least half way through."

Penny shook her head to get rid of the images the statement conjured. "Why the hell was Leonard even in your head at all, Sheldon? We were having sex, was that not interesting enough for you? Were you doing equations on your imaginary whiteboard again, too?"

He scowled at her. "No. On the contrary, Penny, it was a very interesting experience." Gee, thanks, she thought. "Leonard was only there because I suddenly became aware that…well. That I didn't find the notion of you having intercourse with him… agreeable."

She took a second to translate it, and then another to digest it.

He had been jealous.

That…that could explain a lot.

"Sheldon…is that why you told him what had gone on between us? Because you were jealous?"

"Well, yes."

"And not because you wanted revenge for the stunt he pulled at the arctic?"

He looked uncomfortable for a minute. "Well, that was a mostly unintended but admittedly highly satisfying consequence."

She smirked at his discomfort. "So revenge too, huh. Isn't that a little beneath the beautiful mind of Sheldon Cooper?"

He scowled again. "Well I would also have considered myself above the notion of experiencing jealousy over a female, but it looks like I'm learning a lot today now, doesn't it?" He tilted his head with the question, and she briefly thought who says he can't do sarcasm?

"Huh. Clearly Homo Novus has some more evolving to do." Penny glared at him, but realised that it was impossible to stay mad with him for long now she knew his motivation. She felt a little lightheaded; in the space of three minutes he had admitted to finding her attractive, wanting to have sex with her and getting jealous over her. It was turning into an eventful day. She thought back to Leonard, waiting in the other room, and blushed when she thought about what Sheldon had told him about her.

She couldn't let him off that easily. She fixed him with a stare.

"I think you have one more thing to learn here, Sheldon, and it's not going to be pretty." She advanced towards him until he couldn't retreat any further. "You see, what a lady says in the bedroom – particularly when she's not being much of a lady – should remain between her and her incredibly lucky partner. Do you understand?"

He looked at her, and frowned. "Well, I suppose I accept your premise, although I was under the impression that Leonard would be finding out just how unladylike you were very shortly anyw…arghh!" he stopped suddenly as he felt her fingers wrap themselves around his testicles through his pants. "Wrong answer, Sheldon."

His face froze. Penny twisted.

"Now do you understand?" she smiled sweetly.

"Yes! Yes!" his voice had hit an octave she didn't know he had. She grinned and let go.

"Good. And sweetie?" He looked up at her, wincing as he clutched his swollen genitals, and she planted a soft kiss on his lips.

"I'll be over later to show you just how unladylike I can be."