The Unicorn (1963) by Iris Murdoch follows a thirty-year-old governess named Marian Taylor who has pursued an advertised opportunity to work at Gaze Castle, a remote, Gothic estate in an environment where apparently all estates are termed "castles." Marian responded to the advertisement as a result of a sort of mid-life crisis; she has recently come to terms with the fact that her lover, Geoff, can never love her. Moreover, she is attracted to the high salary advertised as well as the opportunity to teach French and Italian.

When she arrives, she is greeted by one Gerald Scottow (her point-of-contact in the matter of the advertisement), who drives them both to Gaze Castle. On the way, they see that the nearest castle is is Rider Castle, where Scottow tells Marian that Max Lejour, a reclusive scholar, lives with his adult children, Alice and Pip. Max also has a frequent caller named Effingham Cooper, his pupil. Only after she arrives at Gaze Castle does Marian learn that her pupil, Mrs. Crean-Smith, is not a child but a mature woman named Hannah.

It is only slowly revealed that Hannah has been imprisoned in the castle against her will by her husband, Peter Crean-Smith. Effingham Cooper has been in love with Hannah for many years, though his mentor's daughter, Alice, is in love with Effingham. Max and Effingham discuss the figure of the unicorn as being a Christ-like scapegoat: itself innocent and used to atone for others' sins.

Hannah seems to be the titular unicorn, imprisoned when her husband discovered her affair with Pip (Max Lejour's son). She has been imprisoned for nearly a decade by the time of Marian's arrival, kept in the custody specifically of Gerald Scottow, who is himself Peter Crean-Smith's former lover.

Marian convinces Effingham to help her rescue Hannah by facilitating her escape while her husband is away. However, Alice (Max's daughter) learns of the plan and prevents it. When Hannah finally does escape (shooting Gerald Scottow), she drowns herself. Her associate kills Peter too when he returns to Gaze Castle (which she has left to Max Lejour). Hannah's former lover, Pip, commits suicide.