Peggy on one of her many attempts to leave the office on last night's "Mad Men."

Credit: AMC

A review of last night's "Mad Men" coming up just as soon as I collect Indian arrowheads...

"Somebody very important to me died." -Don

"Who?" -Peggy

"The only person in the world who really knew me." -Don

"...That's not true." -Peggy

How many people in the world really know you? A handful at best if you're lucky: a spouse or a lover or sibling or close friend, in some combination, maybe.

Don Draper is not so fortunate. Through his own choices, and then through the fickle finger of fate, he's come to believe he's a closed book to the world except to the real Don Draper's widow, Anna. With her, he felt free to be himself - to be vulnerable but sweet Dick Whitman and not this sonuvabitch role he adopted in Korea and cultivated in the years since - and without her, he feels completely, utterly lost.

But as Peggy points out in the climax of "The Suitcase" - the high point to date of season four, and one of the best episodes so far of this incredible series - Anna isn't the only person who knew Don.

Peggy knows him. She always has.

And maybe, just maybe, she can pull him out of this spiral he's been in since his marriage ended.

Now, an argument could be made that the man Peggy knows so well isn't really him. You might say that Anna knew Dick Whitman, and Peggy knows Don Draper. But it's more complicated than that. Peggy has met Dick. Dick Whitman visited her in the psych ward after her baby was born and taught her the lesson he learned from the hobo. Pete tried to tell her some of the story while Don was AWOL in California, though Peggy shut that down. And at their impromptu birthday dinner at the Greek diner (as opposed to the upscale restaurant Mark invited her to), he casually offers up other pieces of the Dick Whitman puzzle, mentioning Korea, Uncle Mac(*), his father's death, his mother, etc.

(*) Uncle Mac's line about always keeping a suitcase packed sounds very hobo-like, doesn't it?

Peggy doesn't have the whole Dick Whitman picture, but she has enough of it, and she knows Don Draper even better than Anna did. She's been his secretary, his protege, his partner and the closest thing he has to a friend. If anyone can help him through this rough patch, it's Peggy Olson - if he'll let her in long enough to do it. And the moment they share at his desk at the end of the episode - with the squeeze of her hand saying more than any words could - suggests maybe he's ready to do just that.

"The Suitcase" isn't just about how well Peggy knows Don, but about how well he knows her, and the difficulty in finding someone who knows you, and also the dangers that come from too much or too little knowledge.

We already knew how little Mark understood Peggy from his belief that she was a virgin when she met him, but he misses the point to an even greater degree when he invites her family and hated roommate to her birthday dinner. Duck unfortunately knows Peggy too well, having been with her during a vulnerable period, and after she talks him out of defecating on Roger's chair, the two important, pathetic drunks in her life come to blows when Duck makes the mistake of using the word "whore" in front of Dick Whitman. (Don's too blitzed to do much about it, though, and falls at the hands of a man who had actual combat experience where he actively killed men, as opposed to Don accidentally causing the real Draper's death.)

And the thing is, Don knows Peggy almost as well as she knows him. That knowledge can come out in both cruel moments, as when he tells Peggy, "You should be thanking me every morning when you wake up, along with Jesus, for giving you another day," and in more tender ones, like when they finally discuss Peggy's baby. (And they do that in the kind of shorthand that only people who know each other this well can; though she could say the word "baby" once to Pete, it seems much easier to just talk around it with someone who was there and understands.)

Peggy is now comfortable enough with Don - and fed up enough with his recent behavior - that she can insult him under her breath, but she can't quit the SOB. Time and again in "The Suitcase," she puts her coat on and prepares to leave, and though she gives a different excuse each time, the fact is that this place, and this man, have a gravitational pull on her. As she admits to Don at the diner, nothing matters to her as much as that office, and the work they do together there. She was with Mark because she thought she should be with someone, but she's already with someone in the way that's most important to her. She's with Don. There's nothing romantic there, and likely never will be(**), but she loves Don in a different but unmistakable way, and she winds up being there for him on a night when he desperately needs someone to love him.

(**) At the end of season two's "The New Girl" - which was, like this episode, directed by Jennifer Getzinger - I said that I could see Peggy eventually growing into the kind of woman who would be attractive to Don, and that this was a rare case of me not minding a show taking a platonic male-female relationship and making it sexual. Two years later, I'm not so sure. I mean, I think I would buy it if the show eventually went there, but their professional and now personal relationship has become so fascinating without bringing that into it that, if anything, a Peggy/Don affair would feel far more routine than what we have now.

My god, how incredible are Jon Hamm and Elisabeth Moss in this one? Outside of the opening and closing scenes, Matthew Weiner's script is essentially a two-character piece - when Duck or Peggy's mom or Mark wander through, it's to illustrate what Peggy has in her relationship with Don that's lacking everywhere else in her life - and both actors get to play nearly every emotion in the book, and to play them all brilliantly. And almost all of it works in parallel. Both break down sobbing (Peggy after Don has suggested how little he thinks of her, Don after Stephanie confirms Anna's death). Both get to look sad for and protective of the other (Don when Peggy talks of being reminded about the baby, Peggy after Don's phone call). Both get to appear terrified of the phone, and completely lost after the news they get from it (that Mark has dumped Peggy, that Anna is dead). Both get to tear into each other (the Glo-Coat argument), and both get to candidly (almost casually) discuss things with each other that they usually keep locked deep inside. And even in the midst of a heavyweight dramatic episode, both get some wonderful light moments, like Don's reaction to Roger's memoirs or Peggy wryly mocking Don about his one-nighter with Allison.

I know I've said on many occasions ("The New Girl," "The Gypsy and the Hobo") that Hamm has never been better, but damn if he doesn't manage to keep topping himself. The complete vulnerability he shows during the call to California and immediately afterward is astonishing. He's holding nothing back there. And Moss is at his level throughout. With "Breaking Bad" and Bryan Cranston ineligible at next year's Emmys, might this be the episode to finally get Hamm and/or Moss a win? I obviously haven't seen what the other usual suspects like Hugh Laurie and Michael C. Hall have cooking in their seasons, but it's hard to imagine seeing two better dramatic performances on television this year than what these two accomplish here.

But of more pressing concern than real-life awards is whether Don might have finally, finally turned a corner here. I'd like to think so, but we've seen Don briefly recover already this season and then slip back, and the rock bottom of last week wasn't enough to scare him straight. We've also, for that matter, seen Don and Peggy reconcile (as they did in last year's finale) after a period of him being an unbearable ass, only for him to resume using her as his punching bag. I'd like to think that this night of walls tumbling down between them makes things different - that he can't go back to treating her that way anymore, and that having her closer to him (and having confronted the loss of Anna), he can put the bottle away and be the crisp, creative Don Draper we see at the episode's end.

I just don't know if it's that simple. At the diner, Don talks about how in coming up with a campaign, you can bang your head against a wall, struggling to tell an awful idea from a great one, but that eventually, the idea comes to you and all is well. But both acknowledge that the rest of life doesn't work that way, much as they want it to. And much as we all want to see Peggy help Don get his act together - to pack up his problems in a Samsonite and fling it off the roof - we still have a half-season to go, and Don may have farther to fall.

But I want to believe. After most of the episodes this season ended with a door being closed, here Peggy asked Don what she wanted him to do with his door, and (as Simon & Garfunkel's "Bleecker Street" began to play) he asked her to leave it open. That's a start.

Some other thoughts:

-The show has in the past showed Don having visions of his past (falling down the steps at the Ossining house and seeing a scene out of his childhood, or imagining the night of his own birth), so Anna's spectral visit to Don's office (with suitcase in hand!) wasn't outside the series' house style. Given Don's liquid state, though, we could also view it as a drunken fantasy as easily as we could a bit of metaphysics.

-Roger's memoirs are the gift that keeps on giving. Here they not only tell us that Roger once slept with Ms. Blankenship back when she was "the queen of perversions" (and looked more like this), but answer the riddle of his reference to Dr. Lyle Evans back in "The Chrysanthemum and the Sword." "Unnecessary orchiectomy"? Ouch. Ouch. Ouch. Though it does explain a LOT about Bert Cooper, does it not? And I would not be surprised at all if Roger wasn't joking about Cooper having Evans killed.

-Trudy's conversation with Peggy in the ladies' room helps spark more of Peggy's baby remorse and general anxiety - "You know," Trudy says, trying to be helpful but completely misreading her audience, "26 is still very young" - and then briefly freaks out Pete. Think he ever gets comfortable seeing those two together unsupervised?

-For those who don't know the backstory, the boxing match was the second title fight between Sonny Liston and Cassius Clay - or, rather, the first between Liston and the man who was now calling himself Muhammad Ali, even if most of white America refused to call him that for several more years. To this day, the phantom punch that won the fight for Ali is still disputed (just Google the phrase "anchor punch" for several thousand pages on the subject). It's interesting to see Don here hostile to both Ali (who always boasted that he was "the greatest") and Joe Namath (who became far more famous than your average QB with one Super Bowl win entirely because of the guarantee he made before he won it). Even after the interview he gave at the end of the season premiere, he still doesn't quite grasp how important self-promotion is going to become in the culture.

-Also, Stan comments that Clay would make a great ad man, while Don objects to celebrity endorsements as lazy; Ali did, in fact, become a pitchman much later in his career, after he was beloved instead of controversial, but also after his mind and speech were slowed down by too many hits to the head. His D-Con commercials were fun, but had Madison Avenue warmed to him in the mid-'60s, he might have been one of the greatest pitchmen of all time.

-Speaking of '70s ads, Peggy's onto something with her idea of the elephant stepping on the Samsonite case. A similar idea, involving a chimp trying to smash the hell out of an American Tourister case, was a huge hit in the '70s. (And is, amusingly, now remembered by most people as having been an ad for Samsonite. Branding only lasts so long.)

-In listing potential clients for his never-gonna-happen agency, Duck talks about "that queer from Belle Jolie," an obvious reference to the guy who tried to sleep with Sal back in season one. It's five years later; I wonder if he actually came out of the closet or if Duck can just tell. (Or if Duck is, as usual, just being an ass.)

-What exactly does Stephanie know about our Don, anyway? She calls up his office, and even though it's his private line, I'm sure Blankenship answered with some variation of "Don Draper's line." It seemed in the California episode that Stephanie and her mother knew Don as Anna's friend Dick, yet she didn't bother to ask here why Dick is using her dead uncle's name.

-And one more Blankenship point: looks like we're with her for the long haul, as Don explains to Peggy why he hasn't gotten rid of her: "Joan knew exactly what I needed and made sure I got it." Don knows both that he deserves some kind of punishment for the Allison thing, but also that he doesn't need any more temptation while he's in his current state.

-As with everyone other than Don and Peggy, Joan doesn't get much to do here, but there's that funny little moment where we see that Danny and Stan are still scared of her but Joey isn't.

-Ever since Jane first appeared, and especially after she hooked up with blue-blood Roger, fans have wondered if the name Siegel means she's supposed to be Jewish. Adding fuel to that fire is Harry telling her cousin Danny "You're such a Jew" when Danny complains about having to pay for tickets Harry got for free. But it's entirely possible that Harry is just being, as usual, an ass, and trading on the general stereotype of Jews being cheap - that he'd have said the same thing to Stan Rizzo had he complained first.

-I like the brief moment where Peggy pauses in between the men's and women's rooms, not sure where to take Don to vomit - does it really matter in the middle of the night? - and then her reaction to being in the men's room for the first time. (Note the mocking "For a good time, call Caroline" graffiti, referencing Roger's frumpy secretary.)

Let me remind you, as always, about the commenting rules that we first started on the old blog (where you can find my reviews of the previous seasons), specifically the one about respecting other posters (if you can't disagree with someone without insulting them, don't bother) and the No Spoilers rule, which includes no discussion of the previews for the next episode.

What did everybody else think?

Alan Sepinwall may be reached at sepinwall@hitfix.com