An intelligent stage actress, Louise Platt's only memorable screen performance came as the pregnant army wife in John Ford's Stagecoach (1939). She was 24 at the time, not exactly the blushing ingenue type, and she much preferred Broadway. She later appeared in such plays as A Room in Red and White, Spring Dance, The Promise, and, alternating with her sister Jean, as Johnny Belinda. In 1948 Platt created the role of Anne Boleyn opposite Rex Harrison in Anne of a Thousand Days and, the following year, starred with Lee Tracy in The Traitor, the latter produced by her former husband Jed Harris. She later appeared in several television shows, including two episodes of Alfred Hitchcock Presents.