An angel''''s earthly mission takes a wrong turn when he falls in love with mortal life.

Angels Charles and Arthur are sent to earth to assist Item, the unborn child of Jeff and Lydia Bolton, who have been too busy with their careers in the theater to consider having a baby. Charles, Arthur and Item are invisible to mortals and can pass through solid objects, such as doors and walls. Charles is not impressed by the Boltons and tells Item that when she selected them to be her parents seven years before, she selected two of the most selfish people he has ever known. After Jeff, a director, has a long phone conversation with playwright Daphne, who has written a new show for him and Lydia, an actress, Jeff tries to interest Lydia in performing in the play. Lydia complains she is exhausted and bored with the theater and wants to have a child, but Jeff does not. Thinking he may be able to bring the couple closer together and thus hasten Item's arrival into the world, Charles decides to materialize and to pose as a theatrical "angel" interested in backing the new play. He models his mortal manifestation after Gary Cooper and goes by the name of "Slim" Charles. As Slim, Charles gains the couple's friendship while Arthur, still invisible, keeps an eye on Charles' activities. Jeff tries to interest Charles in the play and invites him to their farm in Pennsylvania for the weekend. Daphne is also invited and Jeff asks her to use her wiles on Charles, but with Arthur's intervention, Charles resists her advances. When Lydia confides in Charles that her marriage is in trouble, he convinces her to save her marriage and have a child. Charles and Arthur then arrange for Lydia to seduce Jeff. However, Jeff receives a telegram that Tex, a genuine cowboy who backed his last play, is on his way to the farm. Daphne's actor boyfriend Tony, who has played one too many gangster roles, also shows up. Tex wants to back the new show but is reluctant because Charles has already offered. When Tex suggests they cut cards, like Western gentlemen, to see who will prevail, Charles eagerly agrees and Tex wins. Tony, meanwhile, has been summoned to appear in front of an I.R.S. agent regarding inappropriate deductions he has claimed and tells the agent about the large sums of money Tex and Slim appear to have. After the agent discovers that they have no records at all on "Slim Charles," he begins an investigation of Charles. Meanwhile, using $10,000 he won from Tex, Charles moves into a penthouse apartment and spends lavishly. Arthur is disgusted by his behavior, but Charles insists that he is still working on Item's case and is planning a big dinner party for Jeff and Lydia's eighth wedding anniversary, from which he expects them to become romantic with memories of other anniversaries. Arthur and Item, meanwhile, confer with Joe, another yet-to-be-born child, whose "father" is an unsuccessful writer. Arthur tries to help by transmitting a story idea from his own experience into the father's subconscious. After Jeff and Lydia leave his dinner party, Charles falls into conversation with a man at the next table, the I.R.S. agent. When the agent says he supposes that the dinner party he has just witnessed will be tax deductible, Charles informs him that he does not know what income tax is, has never paid any tax and, in any case, is an angel who will shortly be returning to heaven. Later, Charles is seen talking to the invisible Arthur and is placed in a cell at Bellevue Hospital for psychiatric observation. Item comes to visit Charles, who has lost his ability to vanish and reappear, and tells him that Jeff and Lydia are separating. After Item says a prayer for the restoration of Charles' powers, he disappears from the cell. Joe then reports to Arthur that his father has sold the story Arthur gave him, and therefore, he and his wife should now be able to afford to have a child. Jeff discovers that Lydia may be pregnant and they reunite, much to Item's delight. Nine months later, in a hospital waiting room, Joe's father introduces himself to Jeff, who recognizes him as the author of "The Angel Watches," which he wants to dramatize. Charles and Arthur are also present as they are the newly assigned guardian angels of the children about to be born.