Best episode of Mad Men ever? Quite possibly. This is what went down during it...
A former client returned to Sterling Cooper... and tried to return to Roger's bed! She was a former flame of the partner, one that actually broke his heart. Showing incredible restraint, along with loyalty to Jane, Roger actually turned down her advances. Out of love for his wife, or bitterness toward this woman, it's hard to say. But it was certainly a different side to the typically sarcastic Roger Sterling.
He also tried to help Joan find a job, as she called him early in the episode and said Greg was gonna need more time to study to be a psychiatrist and asked Roger for assistance with employment. After turning down his ex-lover, Roger called a friend and asked if he had an opportunity for Joan (another ex-lover, of course).
But, by the end of the episode, it looks as if Joan wouldn't need this help, after all. Greg told his wife that he had enlisted for the army because it would let him be a surgeon. He'd do a residency in New York and then maybe get shipped off someplace, but maybe not. Greg was excited about this new plan, but Joan was as hesitant about it was any reasonable viewer. Greg joined the army on the heels of Vietnam? This won't end well for him.
The crux of the episode, however, was all about Don and Betty. They had the talk. Betty confronted him with his shoebox and past as Dick Whitman. It was as gripping as television can get.
Don came clean, telling his wife all about his former life, even the most shameful of details, such as how his half-brother had killed himself because Don turned him away. There were no more lies, no more slick attempts at story-telling. This was Don at his most naked and honest and it resonated with Betty. She didn't leave him. She actually seemed to finally appreciate some honesty in their lives.
By the end of the house - after Don had ended things with Miss Farrell over the phone - Betty and Don were trick or treating with their kids. They seemed like a happy family. While the symbolism of the kids being dressed like a gypsy and a hobo may have been laying it on a tad too thick, we loved the final line of the episode: a man answered the doorbell with candy in his hand, looked at Don and asked: Who are you supposed to be?