Three and a half stars.

"Public Relations," the wryly titled episode that opens the fourth season of "Mad Men," isn't an entry point for a newcomer to Matthew Weiner's masterwork. Action is mostly absent. Moods vary from frantic to depressed, and the handsome hero is feeling very cranky indeed.

But the "Mad Men" faithful, who have waited almost nine months to find out what happened after Don Draper, Roger Sterling and a handful of colleagues bolted Sterling Cooper advertising to start their own agency, will be riveted from the opening line, spoken by an Ad Age interviewer: "Who is Don Draper?"

What follows is an extremely Don-centric episode, one that finds him struggling as the face of Sterling Cooper Draper Pryce and the shoulders on which the whole impulsive venture rests.

Weiner has asked that critics who previewed the opener don't say too much about what has transpired since the superb third-season finale, with its exhilarating "let's put on an ad agency" attitude. I won't, because I wouldn't have wanted to know in advance, and neither will you. But time has passed, the new shop is no longer brand new and Don has moved on in his personal life, although what he's moving toward isn't clear even to him.

The episode does the expected fine job of setting the scene for the season ahead while teasing us with a new-look Peggy Olson, a much-in-command Joan Holloway Harris and a Harry Crane, TV guy, who has given up suits in favor of sport coats. We also get a glimpse of Betty Draper's new home life, which is doing nothing to help her clearly disturbed daughter Sally.

Although "Public Relations" is engrossing, it's not until the final scene that the old feeling of exhilaration returns, and we're thrilled to know that Don Draper is back.