This story is based on real events which took place in France at the end of the 19th century.
Marie Heurtin was born deaf and blind in 1885. The film finds her when she is 14 years old, unable to communicate.
Her father, a modest craftsman, can't bring himself to have her confined to an asylum, as a doctor advises him to do, deeming the girl "retarded."
In desperation, he goes to an institution in Lamay, near Poitiers, where nuns take care of deaf girls.
Despite the Mother Superior's skepticism, a young nun, Sister Marguerite, devotes herself to looking after the "little wild animal" that Marie is and strives to enable her to exit from the night in which she lives.