London, the early 1950s. Born deaf, Mandy (Mandy Miller) is mute for most of her childhood. As she reaches school age her family itself is in danger of breaking up. Christine (Phyllis Calvert), Mandy's mother has heard of a residential school for the oral education of the deaf, where the children are taught to lip-read and, through the identification of objects, to speak, but her husband Harry (Terence Morgan) wishes to have her home-schooled. Their disagreement over the child's education results in bitter quarrels until Christine decides to leave him, taking Mandy with her. Mandy finally enters the school, run by a dynamic and gifted teacher, Searle (Jack Hawkins).