For the balance of the season, the brittle, petty, religious intolerances on display—especially from Lord Grantham, who finds the prospect of a Catholic granddaughter "flabbergasting"—serve to heighten the deep sense of loss in the house, upstairs and downstairs. They also set up two other major plot points, both of them rooted in the gospel.
The first is the slow restoration of Ethel, a former maid at Downton who has fallen on hard times and become a prostitute. She comes to live as a cook in the house ancillary to Downton, with Isobel Crawley, Lady Mary's mother-in-law (it's wise to watch the show with a family tree up on your laptop or iPad). Ethel's presence there is a scandal to most, though not all, of the servants and members of the Crawley family. Isobel's maid says she will be tarnished by Ethel's presence; Isobel promptly fires her. The servants of Downton are forbidden to go near the house. Mrs. Hughes, the head housekeeper, soon finds her charges' righteous indignation tiresome.
"Jesus did manage to eat with Mary Magdalene," she says, to a carping Mr. Molesley.
"We can't be sure he ate with her," Mr. Molesley says. "He did allow her to wash his feet."
"Well," Mrs. Hughes says, eyebrows rising. "I'll tell Ethel she has a treat in store."
But Lord Grantham cannot abide this travesty any more than he can abide the Catholic one. He is outraged when the women of his house are invited to Isobel's, to be served lunch that has been cooked by a whore. He marches up to the house and demands they leave; they do not, humiliating him. Their refusal to walk out on Ethel is a kind of holy protest, a deliberate decision to forgive that resonates all the more after the mention of Mary Magdalene. I can't remember the last time I heard Mary Magdalene even mentioned on television, much less referred to in context—and with wit, no less.
The second crucial plot point that follows Sybil's death is an extraordinary and delicate minor masterpiece of writing and acting in itself: the fall, and restoration, of Thomas Barrow. Thomas' history as a gay man in the service of Downton is handled with compassion and dexterity throughout the series, and if the sentimentalism comes on a bit strong here at times, it's no more so than in other characters' arcs. In season three Thomas falls in love with the new footman at Downton, Jimmy Kent. He is cruelly set up by his enemy and sometimes ally, Mrs. O'Brien, who knows Thomas just well enough to perceive the depth of his loneliness, and eggs him on by lying about Jimmy's own feelings. Thomas finally makes an advance; Jimmy doesn't reciprocate, and Thomas is discovered and forced out of the closet. He is fired and to be sent away without a reference, therefore losing both his livelihood and the only community he has on the earth.
The believable surprise is that he is aided in the end by his oldest enemy at Downton: John Bates, who has been released from prison at last, and whose newly tested sense of justice compels him to help. Thomas is also defended by Lord Grantham, who is believably and selectively tolerant with him, and what's more is impatient with the intolerance of his staff; he sees himself in it. When Lord Grantham's judgment is questioned, he quietly asks for anyone who is without sin to cast the first stone.