Mr. Fellowes wrote the screenplay for Robert Altman’s “Gosford Park,” but in his own version of a period drama, Mr. Fellowes dispensed with the dark satire — and censure — that distinguished that film. “Gosford Park,” like “The Remains of the Day” and “Atonement,” limned the grandeur of a fading aristocracy with glints of delusion and corruption. “Downton Abbey” doesn’t have the same subversive core. If anything, it echoes a nostalgia for lost time that suffuses films like “Midnight in Paris” and “The Artist.”

The concerns of Lord Grantham (Hugh Bonneville); his American wife, Cora (Elizabeth McGovern); his redoubtable mother, the Dowager Countess (Maggie Smith); and three eligible daughters are mirrored by a hierarchy of servants with their own parallel web of romances and ambitions. The Crawleys keep their feelings from one another, but they unburden themselves to trusted maids and valets. With a few exceptions, the help is so loyal to the family and its position that any slip in prestige or loosening of standards is taken as a personal dishonor.

“Downton Abbey” is a lighthearted look at the class system that is deeply romantic about affairs of the heart. It’s not hard to see why it was such a hit: the series has a connoisseur’s eye for the most exquisite emblems of privilege and breeding and a fan’s gusto for intrigue and melodrama.

The story reopens in 1916 at the Battle of the Somme, where Matthew is an officer trying to keep his troops alive in an unending cascade of explosions and carnage. One moment he is face down in a bomb crater under raining shells, an injured man twitching next to him. The next he is packing up to go on leave, which includes a trip to Downton Abbey. (He calls to mind the line about the trenches, sometimes attributed to the actor and former soldier Ernest Thesiger: “My dear, the noise! And the people!”)

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Matthew and Mary are still star-crossed; even war can’t repair their derailed romance. That impasse is echoed downstairs, where the love affair between Anna (Joanne Froggatt), a housemaid, and the valet, Mr. Bates (Brendan Coyle), keeps coming unraveled.

The war hasn’t left Lord Grantham’s world untouched: Footmen are called up for military service, and parlor maids have to fill in to serve dinner. Matthew’s pushy, do-good mother, Isobel (Penelope Wilton), has wheedled Lord Grantham into giving over part of the house to a convalescent station for wounded officers, where his youngest daughter, Lady Sybil (Jessica Brown-Findlay), volunteers as a nurse.

Season 2 pays lip service to a war that slaughtered a generation and battered the British class system — there are allusions that recall “Regeneration,” the World War I trilogy by Pat Barker, and Vera Brittain’s memoir, “Testament of Youth.” But they are made in passing.

A little like the movie “War Horse,” which is more about the horse than about the war, this series isn’t interested in using its main characters to explore the war’s devastation and tectonic social shifts; combat serves as a plot point and palate cleanser in between voyeuristic looks at high society. So battle scenes and hospital emergencies are clichéd or perfunctory, secondary to exquisite tableaus of swirling chiffon skirts, crystal decanters and lavish country landscapes.

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Even the most devastating wounds are bound up and set aside in time to dress for dinner.

The series’s saving grace is Lady Mary, a Jane Austen heroine who harbors both pride and prejudice. Coolly self-contained and judgmental, Mary is her own worst enemy, but along with withering hauteur, she has self-awareness and a dry sense of humor. Deep down, of course, she has also inherited her snobbish grandmother’s loving heart.

As the Dowager Countess, Ms. Smith has many of the best lines and usually the last word. When her middle granddaughter, Lady Edith, frets that she will end up a spinster, Lady Violet says briskly, “Don’t be defeatist, Dear, it’s very middle class.”

There is nothing middle class about “Downton Abbey.” Even a world war can’t sever the bond between aristocrats and the servants who love them.