Isabel returns to Spain, after several years of absence, to be cured of a neurosis. His daughter Ana, whom he has not seen in all this time, decides to spend the holidays with her, taking advantage of the fact that her boyfriend has gone to study in Germany. During her stay in the sanatorium, Ana meets Mario, an attractive young man somewhat unbalanced, who tries to seduce her. Although at first she does not show any interest, little by little she becomes attracted to him..