Aided by the servant Saturna (Lola Gaos), Tristana breaks her uncle's rules of virtual house arrest to explore the streets of Toledo. The inevitable happens and Tristana runs away from Toledo with her young lover Horiacio (Franco Nero). But there are more things in life than Horacio can dream of and in a few years the couple return to Toledo, Tristana having an extremely painful leg. This is amputated and the course of Tristana's life, in fact much of her psychology, changes and she returns to Lope to marry him.
However, she refuses to sleep with him. And his health declines so sharply that one night he is in agony, close to death. Tristana pretends to call the doctor, and seeing that he is unconscious she opens the window where it's snowing heavily and Lope dies.
*Deneuve surely sets something of a precedent for an original film as her voice is also entirely dubbed in (sung) French in Les Parapluies de Cherbourg: there is only dubbing when she bursts into song in Les Demoiselles de Rochefort.