Of all the relationships on Mad Men, Don and Peggy's has always been one of the most complex and compelling. On Sunday night, it got even deeper and served as a catalyst for their own personal development.

This week's episode sure was a doozy. Not only was it perhaps the best episode of a strong season, but it's definitely in the running as one of my favorite episodes of the entire series. For a show whose hallmark is its craftsmanship, this was just such a wonderfully focused and beautifully constructed hour that I'm still trying to unpack all the delightful things that we learned both explicitly and implicitly about the denizens of Sterling Cooper Draper Pryce. But what was great about it is that everything happened through the lens of Don and Peggy's interactions.

It started off slowly, with Don chewing Peggy out for doing a sloppy job coming up with an idea for Samsonite. Don gives her the wilting backhanded compliment, "I'm glad this is an environment where you feel free to fail." She gets a little huffy, but leaves his office to go work with her team to create something better. Of all the people in the world, we know that Don's approval means more to Peggy than anyone else.

When he finds out that Roger is taking sober associates to the movie theater to watch Mohammad Ali fight Sonny Liston, Don decides he'd rather stay in the office and work on Samsonite. Did Don do this because he didn't want to endure an evening with Roger and a bunch of AA groupies, was it because he really needed to focus on the account, or was it because he couldn't go a whole evening without having a cocktail? It was probably all of those things mixed in with the fact that he got an urgent message from California, probably some bad news about his friend Anna.

Peggy is on her way out to her birthday dinner with her boyfriend when Don calls her into his office and wants to hear what new pitches she has for Samsonite.

[There was a video here]

Their confrontation is that of any couple in a long term relationship. It starts off with little annoyances and slowly builds and builds until they're in a full-on fight. He hates her ideas and sends her back to work. She tries to delay dinner a bit and calls her boyfriend. She says that she's "sucked into his web," in such a casual way that it's clear that she has bitched to Mark about Don many times in the past. When she tells Don it's her birthday, he says she should go, but he's even more angry than before.

Peggy runs off in a huff and she knows she has an important choice to make—one of many that she'll make this episode. Does she go to Mark and have a personal life, or stay with Don and have a professional one? She chooses to stay with Don. When she calls Mark, he tells her that he planned a surprise and invited her roommate and her whole family. She is even more pissed because the gesture wasn't nearly as romantic as she hoped and because she can't stand her family, particularly her mother who disapproves of her work and would rather she was married and popping out children. Once Peggy has chosen work over their relationship again, Mark decides that he's going to dump Peggy, something she doesn't entirely hate.

She goes back upstairs to Don, but it's not a happy homecoming. Now it's time for their big confrontation.

[There was a video here]

Now all the shit's out on the table! Peggy tells Don that he's a no-good drunk with no one in his life who cares about him. He essentially calls her a little girl who should be thankful that she gets to sit at the boys' table. His biggest insult is one that he's made of her in the past, that she takes everything as an opportunity. He says that like it's a bad thing! For a woman like Peggy trying to make it in a male-dominated world, she has to take every little break she can and manipulate it to her greatest advantage. She has to work twice as hard and hustle twice as fast as the men around her, and when she does she gets her hand slapped for it. Like we saw last episode when Don was angry at Roger's wife's cousin for trying to get a job in a sneaky way, Don has an ironic contempt for people who were as persistent and innovative as he was to get his foot in the door at Sterling Cooper. He always reminds Peggy of the fact that she was his secreatry when he wants to control her, and this time is worse than ever. Peggy goes to cry, privately in the ladies room.

When she's done, just like a daughter pissed at her father, she goes into her room to sulk until Don calls her back into his office to make up. Now that the grievances have been aired the healing can begin. Don wants to talk personally with Peggy and she she scoffs at him, saying that they both like to keep their private lives private. After all, they both have their secrets—Don his identity, and Peggy her secret love child—that could be potentially dangerous if everyone found out. And they find out some more secrets, the Roger is writing a book, that Bert Cooper had his balls chopped off, and that Mrs. Blankenship—Don's old crone secretary—was a "hellcat" of the highest order back in her day.

And the secrets just keep flowing. By now Don is nicely lubricated and on their trip from the office, to dinner, and to drinks he starts to open up to Peggy. This isn't Dick Whitman easing through the cracks of a blackout drunk like we saw last episode, this is something different. This is Don Draper beginning to integrate his two identities. He tells Peggy all sorts of things that he wouldn't have in the past: that he grew up on a farm, that he watched his father die, that he never knew his mother. They seem like small disclosures, but for someone who has built a fortress around his past, they're milestones.

We hear a bit about Peggy too. She also watched her father die when she was 12. Also her mother resents Don because she thinks that he is the one who knocked Peggy up. Peggy confesses that she hates that everyone thinks she got her job because she slept with and Don. He tells he that he thinks she's "cute as hell" but he seems to have a lot more respect for her than he did for his other secretaries—including the unfortunate Allison who he bedded and treated like shit. The pair have gone from behaving like a married couple to something closer to brother and sister, enjoying each others camaraderie and trading on their shared experiences with zero sexual undertone. But they both have limits about what they'll disclose. Don doesn't tell Peggy his mother was a hooker and she doesn't tell Don that Pete is her babydaddy.

When they return to the office, Don is completely shitfaced and Peggy has to help him to the bathroom, this is where she is confronted with the most important choice of all.

[There was a video here]

Notice how she pauses briefly in front of the two bathrooms and doesn't know whether to drag Don int' the women's room with her or venture into the men's with him. This whole episode was really about Peggy making it into the men's room, which is essentially what she's trying to do at SCDP. It's someplace where she isn't allowed, and when she finally breaks through the door, she sees a lewd and damaging comment about a woman scrawled on the wall. It's not only someplace she's not allowed, it's someplace she's not wanted—at least not as an equal.

But the women's room isn't much better for her. The first time we see Peggy in the washroom she's confronted with Megan, the beautiful secretary that reminds her of what she once was, and the pregnant Trudy Campbell (in a killer maternity dress and matching gloves!) who reminds her of what she could have been. When she talks to Trudy she knows that she was once knocked up with Pete's baby too, but she wasn't resplendent and enjoying every moment like Trudy is. Peggy hated being pregnant and turned away from it. Trudy acts like Peggy is less of a woman for doing it and discounts all the career choices Peggy has made. "Twenty-six is still so young!" she says on her way out, telling Peggy that she's only really worth something if she marries and has children, and there's still plenty of time.

The next time we see Peggy in the ladies' is when she's crying after her fight with Don. Though she's upset, she refuses to cry in front of Don and takes what can be considered a "female" reaction to the rest room, a place where her behavior is more appropriate. Peggy can't let the men of the agency see her weak or "acting like a girl." In fact they treat her like one of the boys, joking about her farting in her office. The first time she's caught crying she'll lose all the credibility she's worked so hard to build.

But now she's made it to the men's room, the place where she wants to be, and it's horrible. Don is barfing in the toilet, the place is disgusting, and she's left literally holding Don's hat. She's worked so hard to be a part of their world, but the urinals are strange and ugly and it's not nearly as nice as she thought it would be. The most telling detail of all is that when she's in the men's room, she falls into stereotypically female behavioral patterns. She tries to help Don and nurture him, being maternal and acting like she's his secretary. Roger Sterling would never ask Don if he wanted some water, he'd just laugh while Don puked! Though she adopts a masculine edge in the office, Peggy still can't eradicate all of the feminine impulses she's been forced to accept by society. We saw this earlier when Peggy was sitting in Don's office and saw a mouse. She jumped onto her chair, the cartoon gesture of what a woman should do when there's a rodent in the room.

The most self-aware thing Peggy said all night is, "I know what I"m supposed to want but it never feels right or what's as important as what happens in this office." Peggy doesn't want to get married and have kids and have that traditional life. But she's also a woman and she can't behave like the men. Peggy is trying to make it through this treacherous circumstance with no role models of her own. That's why she makes so many mistakes and fights so hard. Who is going to teach her how to do things? Don? He's a drunk mess with no life! I know I'm often hard on Peggy, but I love her, I really do. And more importantly than that, I really have a lot of respect for her. Of everyone on the show she really has the toughest fight and the most to lose.

Yes, I still respect her even though she slept with Duck Phillips, who showed up again this episode. Last season Peggy slept with him in a moment of weakness when she was feeling undervalued at Sterling Cooper and was a little bit lonely in the romance department. That's OK, Peggy, we all make stupid mistakes. Turns out Duck has lost his job at Grey and wants to open a new agency with Peggy that will make ads geared towards women. He even made up business cards for her as a birthday gift. It's a great idea, but one Peggy knows won't work with Duck, who is back on the sauce and a total disaster. When his business pitch doesn't work, he goes for the personal, telling her he still loves her.

After her journey into the dreary depths of the men's room, Peggy finds Duck wandering around the office trying to take a dump in Roger Sterling's chair. Don is none too happy when he spies his former adversary wandering around the office.

[There was a video here]

This was an evening of fights. Aside from Don and Peggy's back and forth, the Ali/Liston drama underscored the whole evening, like the bass notes to a jazz song, plodding the action along. Don said earlier that he was rooting for Liston, who was quiet and strong and that he hated Ali's arrogant showboating. When Ali quickly knocks out Liston, it's like a victory for the modern age. The loud-mouthed flashy celebrity culture that we are currently basking in was inaugrated with that winning blow. "Broadway" Joe Namath, another figure known for his colorful persona, is also about to take center stage in the culture, and Don doesn't like him either.

And now here's Duck, another showy personality who is always out to schmooze and finagle his way through life, and Don just hates him. When he confesses that he and Peggy were in love, Don has no reaction, but when he calls Peggy a whore Don behaves like any older brother would and takes a swing at Duck. Don is too drunk to connect, and these two sloppy mad men end up tussling on the floor like some sort of sad comic strip. Lucky for Duck, he wins, and Don says uncle (if we really wanted to get all English major about it, we could draw a parallel between Don saying "uncle" and Sally masturbating to the show Man from U.N.C.L.E., but we're not going to go that far). Just like Liston/Ali, the big mouth wins—and quickly.

Don retires to his office, and Peggy shortly joins him and they sleep together. No, not like that. All the married couple dynamic is gone now and Peggy has acted like his sister and his caretaker. Now she's his comforter, with his head in her lap as they pass out on the couch in Don's office, the personal and the professional finally merging after a long night of confession and catharsis. Don tells Peggy that he has to do something that's going to be very difficult—he has to call to find out that Anna, the real Don Draper's ex-wife and the one person who connects Don to his past, has passed away. He knew she's been sick and he instinctively knew she was gone but had been avoiding the information all night with the distractions or work, booze, and Peggy.

When he makes the call, it's almost more than he can bear.

[There was a video here]

We learn several things here. One, Don is a much better crier than Peggy. He really gets in there and sobs while Peggy is always trying to hold back a little bit. Secondly, he feels that Anna is the only person who really knew him. He's not crying for Anna, because she's gone, he's crying for himself. Usually I'd chalk this up to Don's selfishness, but isn't all mourning more about the mourner than the deceased? It's even worse for Don because now that Anna's gone it's up to him to keep his past (and that little Dick Whitman who lives inside him) alive. He also feels completely alone in life. Betty has left him for a better man, his kids are strange and foreign to him, even his work associates like Roger Sterling aren't his real friends. He's just a sad lonely man with nothing in his life but his job and even that is tentative in his new business venture.

But Peggy comes over to console him. She steps into the role that Anna once had. Don seems to always have two types of women in his life, the ones that he relates to, loves Platonically, and shares his emotions with and the kind that he lusts after but keeps at a distance. Anna and Peggy are the former and Betty, Bobbie, Midge, secretary Allison, psychologist Faye, and the rest are the later. The only one who ever came close to bridging the two was Rachel Menken in season one, but Don was too afraid back then to really get serious with her. Just like that relationship fell apart, Don now sends Peggy home so that he can be alone.

When she comes into his office in the morning she opens the door and see's Don all fresh and slick. The vomit is off of his shirt, his hair is all in place, and he looks wonderful. At first we expect that she'll get the same treatment as secretary Allison, where Don pretended that everything that occurred the night before didn't happen. But Don, for the first time in a long time, surprises us. He presents her with their new campaign for Samsonite based on Mohamed Ali's win against Sonny Liston. "The Champ." They look it over and Don grabs Peggy's hand. It's not a sexual gesture but one of friendship, one that says "everything we went through last night was real and it mattered and thank you."

For her part, Peggy seems a little uncomfortable but happy. She doesn't so much hold his hand but let's him hold it, happy to be there for Don as a confidante and caretaker. As something that approaches his equal. He's her father, her big brother, her mentor, and her lover all at once and she's finally gotten his approval.

When she walks out of his office she asks if he wants his door open or closed and he says, "Open." It seems to be a whole new day for Don. Instead of his past dying with Anna he seems to have accepted that it now has to be a part of his everyday life. Peggy is not a replacement so much as an evolution, a way for all the facets of his personality to come together. He can't be a closed-off miserable drunk for the rest of his life. Now he's "open," to his future and his past. His survival hinges not on perpetuating the lie that he has created, but somehow overcoming it. But tearing down his emotional walls and being more honest, more vocal, more like Ali. The showy have defeated the stoic and we hope, for this one shining moment, that Don is learning to become a better person.