Determined to educate the town's illiterate children, spinster schoolteacher L.C. Moffat (Bette Davis) opens a school in the tiny Welsh coal-mining community of Glansarno. Battling the contrary local squire (Nigel Bruce), Miss Moffat becomes increasingly discouraged until she sees extraordinary potential in one of her older students, Morgan Evans (John Dall). When Morgan fathers a child out of wedlock, the teacher fears her pupil's chance at an Oxford education may be destroyed.