Suddenly they became small and scrappy without the huge accounts, vast office space and bottomless expenses of yesteryear. And that final episode, as Don banded his loyalists together to start a new firm, was the most exhilarating moment of the season.

Now, at the beginning of Season 4, which begins next Sunday, it’s a year later, and the executives of Sterling Cooper Draper Pryce go on cattle calls to woo clients. Contracts melt away. The business is precarious and copywriters stoop to publicity stunts to gin up business.

His personal life is just as altered. Betty is freshly embarked on a new marriage with Henry Francis (Christopher Stanley), an older man and an aide to Nelson Rockefeller. Henry, who has grown children from a previous marriage, promises Betty a better life  though this one comes with a scornful mother-in-law.

And Don, who had women falling over themselves trying to get him into bed when he was married, finds himself alone in a dark Greenwich Village apartment, shining his own shoes and going out on blind dates. Being a bachelor back in those days, before the pill was widely used by single women and the arrival of “The Sensuous Woman,” did not automatically include swinging. Don tries to kiss a young woman in the back of a cab but can’t get any further. She won’t let him accompany her to the door to the Barbizon, then a women-only hotel, because, as she puts it coyly, “I know that trick.”

Image Betty, played by January Jones, is freshly embarked on a new marriage in Season 4. Credit... Carin Baer/AMC

“Mad Men” keeps confounding expectations  the ’60s fashion, mores and cultural landmarks keep getting more familiar, but the characters maintain an elusive weirdness. Betty looks like Grace Kelly, but she seems blandly prosaic  except when she picks up a BB gun and shoots the neighbor’s pigeons, a cigarette dangling from her perfectly curved lips.