After a prolonged hiatus, “Mad Men” (8 p.m., AMC) returns with a two-hour episode that sets out to answer some questions we’ve been asking for too long; chief among them: Just how will everybody adjust to Don’s (Jon Hamm) impetuous proposal to his secretary, Megan (Jessica Pare)?

Megan’s vitality immediately changes the chemistry of the show and the social hierarchy at the ad agency of Sterling Cooper Draper Pryce. She drags the show and its characters further into the youth-quake pop culture of the late 1960s, especially affecting the dynamics of the show’s strong supporting female characters. Peggy (Elisabeth Moss), always the series’ proto-feminist striver, seems more embittered in the episode’s early goings. Joan (Christina Hendricks), originally seen as a throwback to the 1950s, just may be the biggest “career gal” of all. Don’s ex-wife, Betty (January Jones), does not appear in the season premiere, but Don does refer to her and her older husband, Henry, as “Morticia and Lurch” when dropping the kids off after Memorial Day weekend. And no conversation about “Mad Men” and its female leads would be complete without mentioning Don and Betty’s daughter, Sally (Kiernan Shipka), one of the more complex and troubled adolescent characters ever to appear on television.

As always, “Mad Men” is a feast for the eyes and the mind, a combination of well-drawn characters, cracking dialogue, gorgeous cinematography and pitch-perfect production values.

Tonight’s other highlights

• Scheduled on “60 Minutes” (6 p.m., CBS): Chrysler’s resurgence, a wrongfully convicted man, tennis star Novak Djokovic.

• Scheduled on “Dateline NBC” (6 p.m.): offers too good to be true.

• Emma is kidnapped on “Once Upon a Time” (7 p.m., ABC). Roger Daltrey of the Who provides the voice of a magical caterpillar.

• Musk oxen get territorial on “Frozen Planet” (7 p.m., Discovery).

• Alicia investigates a police shooting on “The Good Wife” (8 p.m., CBS). Matthew Perry guest-stars.

• Gaby needs income on “Desperate Housewives” (8 p.m., ABC).

• Jerry envisions another big score on the series finale of “Luck” (8 p.m., HBO). HBO recently announced that “Luck” will not return for a second season.