Every year, on the anniversary of young John Chandler's disappearance, Rev. Harrington preaches the story of the prodigal son to please wealthy, chair-ridden Katherine Chandler, who has waited for her son to return for twenty-seven years. Fearing that John will be unable to find her, Katherine refuses to vacate her elegant old apartment when the building is sold to the local university to be used as a mens' dormitory. When the university's liaison, Parsons, is sent to evict her, she produces a lease that is cancelable only at her own option. Parsons and the board hope that the renovation and removal of the old-fashioned elevator will drive her out, but Katherine charms the workmen into hammering only after she awakens in the morning. At the beginning of the term, the dormitory proctor, Phil Wilson, tries to keep the high-spirited men under control, but several jokers knock on Katherine's door. Surprised by the grandmotherly figure who answers, the students are shocked into respectfulness. Amused by their antics, Katherine graciously invites them to return during "visiting hours" for tea. At tea time, several young men, dressed in suits, show up, and after an initial awkwardness, warm to Katherine, whom they call "Nana." Phil tells her the disadvantages of living with rowdy students, but soon the men install a bellpull in her apartment and devise a system for efficiently clearing the hall of unclad men when Katherine leaves her apartment for outings. The men take turns assisting her longtime friend and chauffeur, Tom McKay, by carrying her in the wheelchair down the steps. The arrangements are working smoothly when, one night, a brassy young woman, Julie Horton, breaks into her apartment through the fire escape. Enchanted by Katherine's old-worldly spell, Julie confides that she is trying to reach her boyfriend, John Chandler, to make up after a quarrel. Hoping that this John is related to her long-lost John, Katherine sends for him and finds that the troubled ex-Marine bears physical and emotional resemblance to her son. However, Tom, after being introduced to the student, gently advises that Katherine protect herself from disappointment. Meanwhile, troubled by poor grades and his many run-ins with Phil, John quarrels with Julie over her reputation as the college "tramp" and gets into a fight with Phil. When John's roommate Eddie reports that John is to be expelled, Katherine visits the school authorities. After explaining how the expulsion of her son from the same university resulted in unhappiness for three generations, she offers to move out of the dormitory after the term, if they will give John another chance. The board agrees, and John, who is touched by her efforts, begins to change. His grades improve, and he and Julie spend more time with Katherine. Near Christmas, while Katherine and Tom are out, Julie again slips into Katherine's apartment, where John is reading Shakespeare, and the two make love. At the end of the term, John learns that he has passed, but tells Katherine that he is leaving school to earn money for the pregnant Julie, who is putting the child up for adoption. While appearing to support his decision, Katherine tactfully helps the young couple change their plans. Julie moves in with Katherine, and John, who continues with school, gets a job at the university. The night before John's parents are expected to visit, Katherine prays for the reuniting of her family. The next morning, Julie finds that Katherine has died in her sleep. For the last time, the young men carry Katherine down the steps. At her funeral, Tom tells the one hundred and fifty young men, who have become her family, that Katherine's troubled son died many years ago after an accident in a stolen automobile. Although the son gave hospital officials an assumed name, Katherine's husband eventually learned about his son's death and made Tom swear to keep the secret. Tom, who has dreaded all these years that Katherine would learn the truth, concludes that Katherine waited for her son to come home, but finally went home to him.