The main event: Mad Men

Who is Don Draper?" is the question that opens the fourth season of Mad Men. It's an insider's joke, a wink at viewers who have spent three years burrowing into the cryptic ad man's buried secrets and damaged psyche.

The TV drama about Manhattan's advertising world in the early 1960s isn't just a cult favourite; Mad Men has become a cultural phenomenon much in the way The Sopranos once was.

The two shows are mirror opposites of course. The Sopranos amused viewers with unexpected glimpses of bourgeois ordinariness – lawn mowing, school meetings, psychotherapy – inside the scary, alien world of organised crime. Mad Men offers a far more commonplace milieu – the rat race – and finds comedy in the distortions of a rear-view mirror.

There lies the spectacle of people just like us doing things that today seem scary and alien, like smoking, drinking old-fashioneds at lunch, letting children play with dry-cleaner bags.

It's a series set in the days of ice-cold martinis and cold war anxiety that has seduced contemporary fashion, advertising and even the English language.

And accordingly there is Mad Men overload in the air and, in some corners, even a backlash. Fortunately the series' creator, Matthew Weiner, has found a way to finesse Mad Men fatigue at the end of the third season by giving his story a makeover.

Sterling Cooper is starting over, as Sterling Cooper Draper Pryce, and so is Don. When the series began in 2007, its main characters were established, slightly jaded players in a field that was on top of its game in a nation still puffed up with post-war confidence and superpower brio. The advertising firm's creative director, Don Draper (Jon Hamm), married to lovely Betty (January Jones) with two lovely children in a lovely suburb, had little to prove, except, perhaps his effortless prowess as an extramarital ladies' man.

But when Sterling Cooper's British parent company was sold at the end of last season to an even bigger advertising behemoth, Don and his colleagues broke away and lost their complacency. 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 four, 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.

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.

The narrative snakes through a Life magazine timeline of political turmoil and social change – the John F Kennedy assassination is a transforming event, and so are the poems of Frank O'Hara and the songs of Bob Dylan. In the season premiere, a character cites the killing of Andrew Goodman, the civil rights volunteer who was murdered with two co-workers in Mississippi. It's a mention that marks the year as 1964 and the mood of the US as nearing boiling point.

But it isn't always obvious to those living in it. Copywriters goof around at work. Peggy and a young colleague jokingly coo the names "Marsha" and "John" at each other, an oblique nod to Stan Freberg, an ad writer and comedian who had a huge hit in 1951 with a recorded single, John & Marsha.

Don has dinner at Jimmy's La Grange, a Midtown restaurant favoured by advertising executives where chicken a la Kiev is a speciality, and diners are given bibs to protect them from the splatter of butter.

Those kinds of oblique references tether the fictional world of Sterling Cooper Draper Pryce to the real advertising world of those times. That's partly professional pride on the part of the writers, who dread complaints from old ad executives. But those cues also hold out the promise that the coming season will once again pivot the story on the workplace. It's where Mad Men started and where it was best. A fresh start at the rat race is just what the series needs.

Mad Men begins on Wednesday at 10pm on BBC4