[1] The book begins with the arrival of Marian Taylor, a young English school teacher who has accepted a position as governess at an isolated country house called Gaze Castle.

She learns that Hannah has been confined to Gaze and its grounds by her husband Peter for seven years as punishment for having been unfaithful to him and for nearly killing him.

He and Marian try to take advantage of Gerald Scottow's absence to abduct Hannah in Effingham's car, but the attempt fails.

On his way back to Gaze after hearing of Gerald's death, Peter is killed when the car in which Denis is driving him from the airport goes into the sea.

[2] Murdoch biographer and critic Peter J. Conradi notes the author's effective use of "the stage props and scenery of the Romantic sublime", including massive cliffs overlooking a dangerous sea, isolated castles, mysterious megaliths, and a deadly bog containing carnivorous plants.

Their discussion of the situation at Gaze Castle in Chapter 12 deals with power, freedom, suffering, and especially with the nature of "goodness".

[6][7] The relationships among the characters also illustrate the connection between erotic love and power relations that runs through Murdoch's fiction.

[5]: 456  The New York Times reviewer emphasized the novel's Gothic characteristics, and commented that it "has that magnetic quality that is more usually the attribute of the detective story".

[3]: xiv  She has been criticized for exercising a "tyranny of form over character" while writing "according to the dictates of an obsolete standard and within the context of tired patterns".

[6]: 359, 360  Conradi, on the other hand, argues that Murdoch's closed novels, of which The Unicorn is one, were not mere experiments in genre fiction, secondary to her more character-driven works, but were "central to her purpose".

[4]: 118  A later academic interpretation of The Unicorn argues that Murdoch metafictionally deconstructs her own elaborately Gothic setting and story by encouraging the reader to see through the characters' self-deception.