In a season marked by the slow but steady disintegration of Don Draper, both the man and the legend, it's hard to know if this is the moment that Don hits rock bottom, or if this is just the moment that he gains a key ally before the leadership crisis hits the agency in full force. Regardless, this seemingly sparse episode, focusing almost entirely on Don and Peggy, demonstrates why "Mad Men" is at the top of its game.
After Don's mistakes in the previous episode, he and Peggy were going to have it out sooner or later. I just didn't think it would happen so quickly. Longtime fans remember that Don was the one who took Peggy under his wing and, from a certain point of view, saved her from her own mistakes and errors in judgment. As terrible as he is at it, Don's still trying to watch out for Peggy and help her grow, and no matter the opportunities that may arise, Peggy chooses to stand by him.
This is critical, because Don's latest collapse further into the abyss is prompted by the death of Anna Draper. Anna was the one person who really knew Don's true self. Dick Whitman all but died in this episode, right alongside Anna. But Peggy, out of everyone in Don's world, has seen the man behind the legend. The conversation in the bar gave her another good look at everything that Don usually tries to deny. And that opens the door for Peggy to be just what Don needs: an anchor.
And an anchor will almost certainly be needed. That tape of Roger's memoir was not included as a throwaway comedic moment. It was designed to underscore how Roger and Bert are being perceived, and also points to the potential for Don to break away from them, even if he appears to be on the same path.
This is likely why the writers have been emphasizing that Peggy has no romantic designs on Don (and in fact resents the assumptions of such), and have the two of them gush over the rewards of the creative process. Peggy and Don resonate at their creative cores, and that's the part of Don that holds the most potential for rebirth. If anyone is going to help Don survive when the Coopers are eventually confronted (and I strongly believe that will come at the end of the season), it would be Peggy.
The end of the episode suggests that Peggy's presence during this long night of the soul was a turning point. That open door could represent a reversal: instead of shutting out the world, Don is willing to engage again. If Don must abandon his notions of keeping Dick Whitman and Don Draper separate, then having Peggy as a touchstone is pitch perfect. And even better, that deep friendship has been waiting in the shadows since the very beginning.