NEW YORK: In the grand domain of splendid characters at Downton Abbey, Mr. Carson is perhaps the first among equals. Among the superb cast of "Downton Abbey," a similarly towering figure is Jim Carter, who plays him.

After all, this is the saga of a noble estate and those who populate it during Britain's post-Edwardian era, and Mr. Carson, as its butler, is the one who makes that house run.

He bridges the gap between the upstairs elite and the servants bustling downstairs. His word, putting forward the policies and whims of the aristocratic Crawley clan, is law for those in his charge.

Bringing him to life is an actor who makes Carson's crustiness heroic, his unwavering sense of duty lovable to the viewer.

With "Downton" returning for its sixth and final season (Sunday at 9 p.m. EST on PBS), Mr. Carson's humanness will be exposed more than ever as his torturously arm's-length courtship of head housekeeper Mrs. Hughes (played by Phyllis Logan) finally blossoms.

"It was the slowest-burning romance of all times," says Carter with a laugh. "But the audience seemed to want it to happen as did we."

What happens, including an unlikely interlude in this first episode "which hopefully will melt hearts across the country," is only one among many resolutions as the series comes in for a landing in the mid-1920s.

What will be the fate of the financially distressed Downton Abbey estate, presided over by Lord and Lady Crawley (Hugh Bonneville and Elizabeth McGovern) with a less and less sure hand? Will their daughter, headstrong Lady Mary (Michelle Dockery), deign to say yes to her latest suitor? Will the sad-sack valet Mr. Bates (Brendan Coyle) and his wife, lady's maid Anna (Joanne Froggatt), see their dream of parenthood cruelly denied?

Viewers have awaited these and other answers from a costume drama that, since its US debut five years ago, has reigned as a lavish and literate phenomenon.

For the British-born Carter, 67, the road to "Downton" began long ago when he dropped out of law studies at the University of Sussex and joined a fringe theater troupe he equates with "a door to the promised land."

Stage, film and TV jobs followed in a career that has kept him busy and happy, enjoying the process of playing each role free from worry over how the finished product might fare with critics or the public.

"I have no ambitions in the acting world," he explains. "I just need to get out of the house and work and be with people."

After auditioning for Mr. Carson, he thought that piece of acting work would be nice to land, "and I came away thinking, 'I should be very cross if I don't get it.'"

One thing he particularly liked was how Carson's starchiness and pomp had a humorous edge.

Julian Fellowes, who created "Downton Abbey" and wrote every episode, "knows it's funny," notes Carter, "when my character says things like, 'A MAID in the DINING ROOM with a DUKE?! Over my dead body!' And I relish playing those moments."

But even just opening the door to the dining room and intoning, "Dinner is served, my lady," Carter (like the actor who plays him) cuts an imposing figure.

Here is a big man with a broad, expressive face and, maybe most pronounced of all, That Voice: rolling, stentorian, a treat for anyone who's in earshot.

"I can't sing, can't carry a tune," Carter says when asked about his golden throat, but allows, "my voice is strong." And as soothing as it is authoritative: "Friends used to hand me their crying baby to hold and I'd just hum.

The vibration through my chest would put it to sleep."

His presence, and the voice that issues forth when he speaks, has made Carter recognized by "Downton" fans around the world.

He somehow had escaped notice on a brief stroll from his mid-Manhattan hotel down to Herald Square. "But in Boston the other day, 30 times I was approached," he reports. "Nashville, Tennessee. Cambodia. Ghana. After 45 years of acting, 'Downton' is an unsought bonus, because I've never worked for money or celebrity."

This "gypsy caravan" approach to his career saved him from dwelling on his imminent departure from "Downton," even while shooting a final scene with a swell of co-stars in the downstairs hall where servants take their meals.

"When we wrapped, the other actors were getting weepy, and I thought, 'C'mon!' But then the producers came out and thanked them, and I thought, 'We've got to thank the crew, too, because they've been with us every inch of the way.' So I said, 'Guys, all your hard work, your artistry ' And suddenly I couldn't speak.

I began to weep along with the other actors and all these big tattooed guys on the crew with tears pouring down their faces."

"I genuinely hadn't anticipated that," Carter marvels thoughtfully.

But before this final season is done, "Downton" fans should expect a few tears, too.