Patricia Neal plays Allison Crawford, a woman who has suffered psychosomatic blindness for a number of years. Upon psychological examination, Allison seems to have a gap in her memory which may reveal the cause of her emotional distress. When she and her husband Eric (Curt Jurgens) move in with her provocative younger sister (Samantha Eggar), Allison uses her ailment as an excuse to do some of her own investigative research. Slowly gaining back her eyesight, Allison finds the missing pieces of her memory. Julian Halevy based her screenplay on Francoise des Ligneris's novel, Psyche 63. Though the titular number is never explained, it has been suggested that it refers to the year in which the lead character suffered her traumatic experience.