Peggy has not been having an easy go of it during the first half of Mad Men's final season. We've seen her collapse in tears on her apartment floor, take out her frustrations on Shirley on Valentine's Day, and repeatedly give Don the cold shoulder since his return to the office. The first two instances made since for Peggy's character. She found herself unfulfilled at work when, instead of taking the boss' chair that she was left in at the end of season six, Lou showed up leaving her lower on the totem pole. Similarly, she found her home life empty because instead of returning to a family that would provide her with a literal sense of security in her sketchy apartment, she goes home alone making sure to latch all of the locks on her door. But the shift in her relationship with Don, that wasn't so clear and, until Sunday night's episode, left viewers wondering why Peggy would be so mad with him specifically.
At first I thought it was because she felt betrayed by her mentor. Peggy and Don have always had a close relationship, so maybe she was upset that he would lose control the way he did and leave her behind. This didn't add up though. Peggy clearly wanted to move forward in her career and the way she reveled in bossing Don around when she got the chance made that apparent. So could it be that her anger came from being annoyed that he got to waltz back into a job after screwing up when she feels stuck at a dead end? That would make sense, but there seemed to be more to it.
When watching Sunday night's "The Strategy" it clicked for me: Peggy wasn't mad at Don at all, she was just taking it out on him. Don wasn't the one blocking Peggy from moving up — that was Lou, and more generally, the fact that she's a woman working in a male dominated job in the 1960s — but, for Peggy, taking it out on Don is a way of proving something to herself. If Don is below her, if she is given the opportunity to manage him, it means that she's moved up. Except she hadn't actually and she begins to find that out when she sees Lou is using her for his own power play with Don. On "The Strategy" she sees it even more clearly when Pete tells her that Don should do the Burger Chef pitch but that it's "her decision." The point is really driven home when Pete says that Peggy is the best woman in advertising.
Peggy, and the audience (if they hadn't already caught on), know then for sure that her anger has been misdirected toward's Don the entire time. When Peggy tells him that she wants him to do the presentation, he can see right away that it isn't true. Later, when they work together on a new Burger Chef idea, their connection is the strongest it's ever been. Peggy and Don can relate personally — she admits that she's lonely, he admits that he worries about his accomplishments — and also professionally — they both have a passion that makes them want to stay up all night talking about ideas. When Peggy and Don dance to "My Way" together, there are no fears that the situation will turn romantic or that their relationship would ever fall apart for good. They know each other too well.
In an interview before the season began, Elisabeth Moss said that there was a moment towards the end of the first half of the final season that made her cry when Matthew Weiner told her about it. She explained, "It meant so much to me, and this other character, that I care about personally and professionally. It was just this very climactic, kind of sweet moment." At the time, I predicted that this meant the start of a romantic relationship for Peggy and Stan, but how naive I was. Peggy will or won't find that kind of love, but that will never be the most important relationship she has on the show. It will always be her relationship with Don. In the final scene at Burger Chef they were their own type of family and now that they understand it, we'll have to see how well it translates into an ad.