St. Mary's parochial school is in need of a miracle. It's run down from lack of repair. It's about to be closed down from lack of funds. And its students are in need of light-hearted relief from the guidance of their no-nonsense teacher, Sister Benedict (Ingrid Bergman). So when high-spirited father O'Malley (Bing Crosby) arrives as the new parish priest, it's the answer to everyone's prayers. For the charming priest wages a good natured battle of wits to loosen the Sister's tight rein. And soon they are joined together to save the beleaguered school from closing its doors forever.