When you get two pivotal characters and let them run the story for 50 minutes, without anyone else - you've got a winner. This wasn't the usual 'Don is drunk-Don is lonely-Don needs a vulnerable little secretary to plant his seed' type story. Rather, it was an alcohol fueled epic buildup to show something we've never seen these 4 years - Don breaking down.
The story starts off with Don getting a message from Stephanie, and he knows it's bad news. He knows he can't handle it, and somehow tries to immerse himself in the Samsonite pitch by making Peggy his scapegoat. The alcohol starts flowing freely from then and Don goes through the various stages of grief. He is in denial, he doesn't want to call up and hear the news first hand. He vents out his anger on Peggy, when she finally speaks her mind on her Glow-coat contribution and how Don never acknowledges her effort. He goes into a brief depression when he can't handle all the alcohol and throws up. He even gets beaten up by Duck Phillips and finally decides to get some sleep. Don finally finds acceptance when he imagines a silhouette of Anna Draper in his drunken state. He wakes up the next morning and makes the call to California, and finally breaks down like you have never seen before.
Matt Weiner knows this is not the Don you want to see. A couple of scenes later, we see Peggy enter Don's office to see his all cleaned up and looking Dapper as if nothing had happened. Don has the pitch ready for Samsonite - a symbolized version of the Cassius Clay fight.
We see an interesting dynamic between Peggy and Don, something we've always waited for and something which we may very well never get in the future. This is definitely Mad Men at its best.