Oswald is a male fantasy figure described as "the greatest fornicator of all time", his adventures recounted by a nephew who inherits his diaries and decides to edit them for publication.

Wealthy gadabout Oswald Hendryks Cornelius is stranded in Cairo when a Syrian businessman picks him up by the side of the road and offers him a room for the night in his desert mansion.

Oswald Cornelius becomes entangled with a Belgian olfactory expert who claims to have discovered an eighth smell-related nerve that, when stimulated, unlocks certain aspects of human sexual experience.

The expert develops a perfume to stimulate the nerve, causing chaos when it is exposed during a high society dinner for an American women's movement that Oswald is attending.

Alfred Hitchcock, for whose television programme Dahl's story "Man from the South" was adapted, was fond of "The Visitor" and in later life recounted its plot on American talk shows as a dark joke.