The burning question: What can deprived fans of the critically acclaimed series, "Mad Men" expect when its fourth season premieres on AMC this Sunday? Though the third season ended with Don Draper breaking away from Sterling Cooper and launching a new agency with a few select colleagues, the show's notoriously secretive creator Matthew Wiener is enamored of unpredictable plot twists. (Watch Weiner discuss Season 4.) Here's what commentators have reported so far:

1. An identity crisis for Don Draper
"The new season is all about what it's like for this very secretive man who has a dual identity to suddenly be front and center as one of the faces of the new agency," says Wiener, as quoted in New York magazine. Now that his true identity has been revealed, and his wife Betty has left him for an older man, Don will have to figure out who he is and how to present it to the world. The season premiere, aptly titled "Public Relations," opens with a reporter asking "Who is Don Draper?" — a question that's likely to shape the whole season.

2. A struggling new agency
The fourth seaons picks up the plot a year after the third season left off — with life at Don's new agency, Sterling Cooper Draper Pryce, distinctly short on glamour — not to mention bottomless expense accounts. "The business is precarious and copywriters stoop to publicity stunts to gin up business... [as] contracts melt away... [and] executives of Sterling Cooper Draper Pryce go on cattle calls to woo clients," says Alessandra Stanley in The New York Times

3. A whole new look
One consequence of Don and Betty's divorce: The show will have a very different look. Don's apartment will have a sad, single-guy feel to it, says Wiener, as quoted by ABC News: "This is the divorced-dad locale. It’s plush and it's velvety and it's masculine and it’s somewhat lacking in personal character… sort of the Oakwood apartments of its day," he says, referring to a notoriously souless apartment complex in Los Angeles, known for housing transient business men and bands.

4. More levity
Laugh-out-loud moments are extremely rare on "Mad Men," but the season premiere is distinctly funny, says Joel Keller at TV Squad: "There are some genuinely funny moments in the episode, many of them involving Peggy, who seems to have grown up before everyone's eyes." On the down side, he adds, "Much of the deep introspection that has made the show a must-watch wasn't there" in the premiere episode.

5. An even less likable Betty
With her Barbie-doll looks and Feminine-Mystique misery, ice princess Betty has always been hard to like. In the new season, she's more insufferable than ever, says Alan Sepinwall at HitFix. To date, "she always garnered some level of sympathy simply because Don was such a terrible husband." Now that she's been "freed of his secretive, cheating ways and [has begun] a relationship with the more doting Henry Francis, Betty no longer has excuses for her own awful behavior — particularly the way she treats daughter, Sally."

6. Don's sex appeal fails him
Between his beautiful, if chilly, wife and seemingly endless string of extramarital affairs, Don has never had a hard time with the ladies, but that changes in the new season, says Roger Friedman at Showbiz411. Divorced from Betty, he's stuck going on blind dates and "sometimes paying for sex."