Peggy Olson had made a lot of mistakes with men in her life. But she always considered one of her biggest mistakes – the type she would never, ever make again – to be Pete Campbell. He was the kind of lesson you learn once and it gets so embedded in your brain that you can never, ever forget it.

Oh, it had been easy to get taken in by him at first. Hadn't that been half the reason people had encouraged her to go to secretarial school? Because it was such a great job for finding a husband, or at least some exciting affairs? Peggy was never interested in becoming that ideal housewife, or sleeping to the top, but if an interesting, illicit romance with a work superior presented itself, she wasn't going to turn it away. Peggy had never been the sort to stick to the rulebook if bending it presented more intriguing opportunities.

And it was clear that Sterling Cooper presented a lot of those opportunities. From the moment Joan Holloway first showed her around the office, she knew it was the kind of place where people followed their desires and things like marriage didn't matter much. It was well-known that just about all the accounts men were sleeping with someone in the office, and Joan herself seemed to be pointing out the men she'd been with and encouraged Peggy to avoid. And as the newest secretary, of course, Peggy was showered with male attention from the moment she started putting away her things.

What was it about Pete Campbell that caused Peggy to pick him? He didn't have the easy charm of the men above him. He was cute, but not overly so. Hell, he insulted Peggy in the light of day, and then came to her apartment drunk out of his mind. He was newly-married. Was it precisely because it was so sleazy and wrong and inadvisable that Peggy wanted him so badly then? Was it because she wanted to burn away any last vestiges of the innocence everyone foisted on her?

And yet, she saw herself start to fall for him. She should have known better; they don't leave their wives, especially not for secretaries. And she should have known that Pete especially saw her as nothing more than a secretary, nothing more than a hook-up, a way to fit in with the other philandering men around the office. There was a reason that he fucked her the morning before she landed the Belle Jolie account – her first-ever copywriting job – and suddenly had no interest later. "I don't like you like this." Like what? As someone with talent, with promise and ambition, someone who could potentially compete with him one day? And she had let herself shed tears over that?

After she got out of the hospital, she took Don's advice. It never happened. Not just the pregnancy, but the whole affair. Her relationship with Pete was no different than with anyone else in the office, and she would have it no other way. He certainly seemed to acquiesce, not approaching her at all for a year and a half beyond mere office cordiality, with maybe the slightest tinges of friendship.

It was over. Clearly over. It was amazing how easy it was, and yet so refreshing.

At least, until he suddenly came into her office and confessed his love for her, tell her that he belonged with her and not Trudy.

Peggy was aghast. She'd expected a confrontation when she'd returned from pregnancy leave, but now? When they'd barely interacted, beyond the professional realm, for over a year? They weren't even friends! How could he have such feelings when he didn't - couldn't - know her? He hadn't even tried! Questions, speculations, spun in her mind. It had to be something in his marriage, Peggy figured, because nothing had happened between them since she had the baby.

And she felt nothing for him – had felt nothing, ever since she recovered from his crudeness during "The Twist." That's why his baby had been so easy to give away. So how could he feel things for her, and expect anything in return other than shock and dismissal? He had to be projecting.

And in the end, it didn't matter. He was a mistake. The kind of mistake you never make again.

It didn't matter what he said. Even if he did successfully manage to ape the charm of a Don or Roger, in his appeals to her. Her explanation and rejection might have hurt him, but it had to be done.

Because Peggy was never going back.