One Romantic Night (1930)
One Romantic Night (1930) is the title given to the first sound film version of Ferenc Molnár's play The Swan, and was silent screen star Lillian Gish's talking film debut. She starred as Princess Alexandra, with Conrad Nagel as the tutor who falls in love with her, and Rod La Rocque as Crown Prince Albert. The film was only fairly successful, though Gish would go on to become as highly regarded in talking pictures as she had been in silent films.
More at Wikipedia.