A voiceover by the child Jeremiah (Justin Pierre Edmund) guides the viewer through the film.
Rev. Henry Biggs (Courtney B. Vance) is the pastor of a small struggling Baptist church in a poverty-stricken neighborhood of New York City. Membership is declining, Henry is pulled in a hundred directions by his parishioner's needs, and the church's finances are in trouble. Henry is under intense pressure from real estate developer Joe Hamilton (Gregory Hines) to sell the church's property so that Hamiltion can build luxury condominiums on the site. Henry has also become neglectful of his wife, Julia (Whitney Houston), and his son, Jeremiah. Julia worries that her marriage is failing. Unsure that he can make a difference in his parishioners' lives and beginning to lose his faith, Henry prays to God for help, which comes in the form of Dudley (Denzel Washington), a witty and debonaire angel. Dudley tells Henry that he is an angel sent by God to help him, but Henry is deeply suspicious of Dudley. Julia, however, is instantly charmed by the handsome and unflappable angel.
With Christmas approaching, Henry's schedule becomes increasingly burdensome, and Dudley begins to spend most of his time with Julia and Jeremiah. Rev. Bigg's secretary, Beverly (Loretta Devine), becomes comically defensive and aggressive, believing Dudley is there to take her job. Julia's wasp-tongued mother, Margueritte (Jenifer Lewis), is also suspicious of Dudley, because she believes the newcomer will break up her daughter's marriage. Dudley and Julia go ice skating, and then later spend an evening in the jazz club where Julia once performed. After Henry confronts Dudley, Dudley realizes that he is falling in love with Julia. Dudley turns his attention to Hamilton, and manages to disrupt Hamilton's schemes to get Henry to sell the church. Henry now realizes that his family is the most important thing in his life, and he resolves to be a better husband and father. At the church's Christmas pageant, Henry finds his faith in God renewed and his ties to his family restored.
With his work done, Dudley gives the Biggs family a fully decorated Christmas tree as a gift. Dudley then erases all memories of himself from everyone he has met, and although he attends midnight service on Christmas Eve, no one recognises him. Jeremiah, who has the faith of a child, still remembers Dudley, and wishes him a merry Christmas.
A subplot present throughout the film focuses on Julia's singing talents. Once a popular nightcub singer, she is now a star in the church choir. This subplot provides for several set pieces in which the choir performs and Gospel music plays a significant role. It also provides comic relief in the form of a domineering choir director.
