On a snowy evening in New York City, a charming gentleman, Cary Grant, leisurely wanders the streets, taking in the holiday decorations and the joyous smiles of children. His kind actions seem almost magical as he helps a blind man navigate the streets and saves a baby in peril from oncoming traffic. When he encounters the lovely yet sorrowful Julia, portrayed by Loretta Young, engaged in conversation with her old friend, Professor Wutheridge, played by Monty Woolley, he feels compelled to lend her assistance. Assuming the guise of an old acquaintance, he gathers information about Julia's struggles from the professor, who is left questioning the gentleman's true identity.
Returning to her home, Julia finds her husband, David Niven, the bishop Henry Brougham, embroiled in a tense argument with the powerful and affluent committee chair, Mrs. Hamilton, portrayed by Gladys Cooper. Henry is passionate about constructing a new cathedral but needs Mrs. Hamilton's financial backing, which she insists must be a tribute to her deceased husband. The marital tension between Henry and Julia is palpable as their relationship deteriorates under the strain of his obsession with the cathedral project. Distressed and overwhelmed, Henry retires to his study, ultimate in despair, and prays for divine guidance.
Unexpectedly, a gentleman named Dudley claims to be an angel who has appeared in response to Henry's prayer. Despite Henry's skepticism, Dudley swiftly endears himself to everyone around—his maid, Matilda (Elsa Lanchester), his little daughter Debby (Karolyn Grimes), and even Julia, who is captivated by Dudley's extensive knowledge and charm. Throughout this, Henry finds himself becoming increasingly frustrated by Dudley's presence, particularly as his plans for the cathedral remain stagnant.
An impending confrontation brews as Henry contemplates yielding to Mrs. Hamilton’s demands to expedite his life returning to normal. Uneasy about his lunch plans with Julia and the choir practice at St. Timothy's, Henry begrudgingly declines Dudley’s offer to visit Mrs. Hamilton, leading to a lively outing between Dudley and Julia filled with lunch, choir rehearsal, and ice skating. While Dudley inspires joy among the choir boys, Henry struggles to appease Mrs. Hamilton, ultimately pledging to fulfill her whimsical stained-glass window requirements, humorously leading to a comedic situation where he gets stuck to his chair.
Later, Henry expresses to Dudley that he is ready for him to leave, believing his prayer has been answered. However, Dudley raises doubts about whether Henry truly desires the cathedral or Julia’s happiness more. Angry, Henry commands Dudley to exit his life. As Dudley departs, he wisely advises Henry not to show such anger to Julia. During a visit to Professor Wutheridge, Henry reveals his fears about losing Julia to Dudley but learns from the professor that his status as a mortal man provides a significant edge over an angel in matters of the heart.
As December 24th unfolds, Henry submits his Christmas Eve sermon manuscript to his secretary, Miss Cassaway (Sara Haden), who is less than enthusiastic about the late hours. Dudley offers to assist, whimsically discarding the manuscript and dictating a new sermon focused on Christmas gifts and goodwill. Meanwhile, as Henry and Julia make social calls, they return home to find that Dudley has moved Mrs. Hamilton with a poignant musical piece that evokes memories of her first love, Allan, resulting in a softened heart and a willingness to support the poor.
With renewed clarity, Henry confronts Dudley, admitting that Julia surpasses all else in importance, thus establishing his priorities. Dudley acknowledges this shift and prepares to depart, stating that Henry had indeed received his answer to prayer—not for a cathedral, but for wisdom. Dudley has one last heartfelt conversation with Julia, confirming he must move on, which she firmly accepts, leading to him removing any remnants of his existence from their memory.
Ultimately, as the community gathers for Henry's transformed Christmas Eve sermon, Dudley stands outside, unrecognized, departing with a smile into the snowy streets. Henry delivers an impassioned message urging his congregation to fill Jesus' stocking with love, kindness, and understanding—all the beautiful gifts that contribute to peace on Earth.
