There’s a lot of buzz in “Downton Abbey” about poor Lady Mary.

Ever since her husband died in a car accident (remember?), she has been moping around the manor, unwilling to do anything. And yet everyone from the downstairs maids to the outside grandma thinks it’s time she re-entered society.

Dad, however, doesn’t want too much participation. With Lady Mary (Michelle Dockery) busy mourning, he can decide the fate of the property.

In the fourth season premiere of “Downton,” there’s a lot of attention paid to “running the estate,” which suggests there’s more here than even the Earl of Grantham (Hugh Bonneville) can imagine.

Downstairs, staffers have to deal with an ever-shifting population (it’s like a department store behind the scenes) and a few friends who are down on their luck.

Anna Bates (Joanne Froggatt) and her husband John (Brendan Coyle) are the ultimate trouble-solvers, figuring out ways to make the upstairs folks happy while reshuffling the downstairs deck. It’s fun to see all the activity required just to allow the wealthy to sit around.

But the fourth season opener suggests there’s going to be plenty of chaos for everyone. In addition to the trouble with Mary, there’s the matter of Lady Edith (Laura Carmichael), who has her own views of happiness, and the moping ways of Isobel Crawley (Penelope Wilton), the late Matthew’s mom.

“When your only child dies, you’re not a mother anymore,” Isobel says. “I’m just an old widow who eats off a tray.”

Leave it to the downstairs folks to figure out a way to get her back into action and on the way to recovery.

Writer Julian Fellowes doesn’t short the Dowager (Maggie Smith) any, either. She noses into all of the problems and admits, “It’s the job of grandmothers to interfere.”

Smith, in fact, is more active in this episode than she was in nearly all of the third season. Elizabeth McGovern continues to be underused and largely ornamental but Carmichael could be the Crawley woman to watch. She’s poised for lots of action.

Downstairs, Thomas (Rob James-Collier) continues to cause trouble for everyone in his wake. He finds a new partner in crime and, together, they stir more than one pot.

Interestingly, technology enters “Downton,” too, suggesting the world they’ve relied upon could be shifting.

A hint of 21st century changes? Parallels could be made. But this is such a juicy character study it’s not easy to go off on tangents while the soap is boiling upstairs and downstairs.

While newcomers may wonder why so much is made of so little, they can’t deny the delicious one-liners Fellowes has written.

Coupled with a driving score, “Downton Abbey” moves – in ways you never thought possible. It's good to see it back.

Downton Abbey” returns Sunday for its fourth season on PBS. It airs at 8 p.m.