context: On a snowy evening, a dapper gentleman (Cary Grant) strolls serenely through the streets of New York City, admiring the Christmas decorations and the smiling faces of children. He seems to be wandering around doing good deeds for others, almost magically appearing at the right place and time. He helps a blind man cross the street and rescues a baby whose carriage is rolling into traffic. When he sees the beautiful but sad Julia (Loretta Young) converse with her old friend Prof. Wutheridge (Monty Woolley), he takes a serious interest in helping her. Feigning an old acquaintance, he gets more information from the professor, who's unsure if they've ever really met, but guardedly tells the gentleman about Julia's troubles. As they part, Wutheridge wonders who the fellow really is.When she arrives home, Julia finds her husband Henry Brougham (David Niven), the Episcopalian bishop of the local diocese, in a heated argument with the chair of the cathedral committee, Mrs. Hamilton (Gladys Cooper), a wealthy but domineering older woman. Henry has a dream of building a new cathedral, and needs Mrs. Hamilton's financial support. Unfortunately, she demands that the cathedral be built as a monument to her late husband. Later, Henry argues with Julia, and it's obvious that their marriage is strained by his preoccupation with the cathedral. Harried and harassed, Henry is at his wit's end, and retiring to his study he prays for guidance. Turning to leave, he is surprised to find a gentleman has somehow appeared in his study. Telling Henry that his name is Dudley, the gentleman reveals that he's an angel, and he's come in answer to Henry's prayer.Despite Henry's doubts, Dudley quickly charms his way into Henry's life, becoming a favorite of his maid Matilda (Elsa Lanchester), his little daughter Debby (Karolyn Grimes), his secretary, his St Bernard Queenie, and even his wife Julia, all the while preventing Henry from telling anyone what Dudley claims to be. Julia enjoys Dudley's company, delighting in his broad knowledge of the world and his ability to do seemingly everything well. Meanwhile, Henry gets no closer to building his cathedral, and becomes increasingly angry with Dudley for being so intrusive.A confrontation looms, and Henry decides to submit to Mrs. Hamilton's demands in order to speed things along, get his old life back, and get rid of Dudley. His visit to Mrs. Hamilton is fraught with tension before he even sets off because he'd agreed to have lunch with Julia that afternoon and hear the boys' choir rehearse at St. Timothy's, his old church. Dudley offers to see Mrs. Hamilton so Henry can keep his appointment with Julia and the choir, but Henry curtly refuses, so Dudley meets Julia. He takes her to lunch, to the choir practice, and then they go skating. While Dudley brings out the best in the boy sopranos, Henry abases himself. In the movie's funniest scene, he apologizes to Mrs. Hamilton for disagreeing with her and promises the cathedral will be built exactly as she wishes. She adds a new condition: in the stained-glass window depicting St. George and the dragon, St. George must have her late husband's face. "Who do you see as the dragon?" asks Henry, and she looks at him a bit suspiciously, but he's all innocence. Having achieved his objective he tries to go, but finds himself stuck to his chair, which prevents him from meeting Julia. Everyone involved  the bishop, the dowager, and her butler  is much too dignified to allow the scene to descend into farce, but it takes some doing to avoid it, with Henry creeping around the room in the hunched posture forced upon him by the chair. Eventually he calls home and asks Matilda to bring him another pair of trousers.Later that afternoon, Henry tells Dudley he can leave; Henry's prayer had been answered. Dudley's not so sure. What does Henry really want: the cathedral, or Julia's happiness? Enraged, Henry demands that Dudley get out of his life at once, and as Dudley departs with a smile, he admonishes Henry not to let Julia see him this angry. Later, visiting Professor Wutheridge, Henry confesses that he's probably lost Julia to Dudley, and is surprised to find that he can actually tell the professor about Dudley being an angel. Wutheridge reminds Henry that he has an advantage over an angel: he is a mortal man, and Julia is a mortal woman.During the afternoon on December 24th, Henry gives his secretary Miss Cassaway (Sara Haden) the manuscript of his Christmas Eve sermon to type. She isn't thrilled to be staying late on Christmas Eve, so when Dudley turns up and offers to finish it for her, she's quick to accept. Dudley tosses the manuscript and incomplete typescript into the fire, orders the typewriter "Take a sermon," and starts dictating a sermon about Christmas gifts and an empty stocking.Meanwhile, Henry and Julia have gone to pay some calls, finishing with Mrs. Hamilton. But Dudley is there before them. Left alone to await her in the drawing room, he finds an old musical manuscript dedicated lovingly to Agnes (Mrs. Hamilton's first name is Agnes) and signed "Allan"  not her late husband's name. When she comes in Dudley's playing the composition on her harp. Hearing it again after many years moves her, and she tells Dudley that the composer, Allan, was the only man she ever loved. They were engaged, but he didn't have any money and because she feared poverty, she broke it off. She married Mr. Hamilton because he was fond of her, and he was very rich. Mrs. Hamilton breaks down and cries on Dudley's shoulder. when the Broughams arrive she's uncharacteristically warm, asks them to call her Agnes, and mentions in passing that she's decided to give her money to help the poor.Back at the house, Henry faces Dudley one last time. Henry tells him that Julia means more to him than life itself, and he's willing to fight Dudley no matter what may happen. Relieved that Henry has gotten his priorities straight at last, a beaming Dudley tells Henry that he's leaving, and that Henry's prayer has been answered. Confused, Henry disagrees. "I prayed for a cathedral," he says."No Henry, you prayed for guidance," says Dudley. "That has been given to you."Dudley has a final meeting with Julia to let her know that he's unlikely to see her again  angels aren't assigned to the same post more than once because they're not supposed to form attachments  but he is tired of constantly moving. She realizes what he's saying and tells him very firmly that he must indeed go away and never come back. When he leaves, Dudley takes with him all memory of his existence. None of the people he's helped remember him at all. As they gather in church for Henry's Christmas Eve sermon, Dudley stands outside, unrecognized. He smiles and walks off into the city. Henry delivers Dudley's sermon, asking his flock to fill Jesus's stocking with gifts of "loving kindness, warm hearts, and a stretched out hand of tolerance: all the shining gifts that make peace on earth."
question: What is Dudley's mission?
answer: to spiritually guide Henry and the people around him