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Nick Briggs, Carnival Films
Michelle Dockery as Lady Mary, left, and Joanne Froggatt as Anna Bates in season four of "Downton Abbey."

Like a thief in the night, Miss O’Brien has left Downton Abbey.

Lady Grantham’s scheming lady’s maid leaves only short notes behind when she makes a quick exit at the two-hour fourth season opening of the wildly popular PBS import, premiering on KUED on Jan. 5 at 8 p.m.

The sudden death of the dashingly handsome leading man, Matthew Crawley (Dan Stevens, off to pursue big-screen successes), caused an uproar among fans in the “Downton Abbey” third season cliffhanger. The departure of a primary villainess is nearly as shocking.

But what follows is a lumbering season premiere.

It’s been six months since the car crash that followed the birth of the new heir to the Grantham estate, and Lady Mary (Michelle Dockery) is still mourning her husband’s death. Actually, she’s nearly comatose with grief — although tastefully restrained about it.

Lady Mary’s best line in the episode is nearly as enjoyable as some of best bon mots of the Dowager Countess (played to perfection by Maggie Smith). Examining her sister’s suitor, Lady Mary remarks, “He’s not bad looking and he’s still alive, which puts him two steps ahead of most men of our generation.” There’s a hint that Lady Mary will be taking on a more active role in managing the estate.

A treat is the unexpected cameo by famed opera soloist Kiri Te Kanawa, quite literally singing for her supper as the real-life Dame Nellie Melba.

Yet the delicious drama returns in the following episodes, and the sophisticated soap opera regains its regular entrancing stride. Soon the full level of romance and intrigue that has made the series so captivating begins anew.

The groundwork is set for more turmoil with Lady Edith (Laura Carmichael) and Michael Gregson (Charles Edwards), her married love interest, in a storyline that too strongly resembles “Jane Eyre.”

The lovey-dovey relationship between John Bates (Brendan Coyle), who is Lord Grantham's valet, and Anna (Joanne Froggatt) continues, but be assured there is a rocky juncture on the horizon.

What will be clear to viewers are the changes coming to the show. As the Roaring ’20s begin, so do additional complications in the upstairs-downstairs dual world of characters. There is still much to celebrate about the return of “Downton Abbey.”