An obsessive believer in the hollow earth theories of John Cleves Symmes, Jr., Briggs is convinced that in Antarctica he will find the entrance to the Inner World and its inhabitants.

Through her inner 'conversations' with him, Sym mulls over what she is told, compares it with reality and gradually frees herself from the deceptions imposed on her by others – principally by her 'Uncle' Victor, and also by the conman Manfred Bruch and his apparently love-smitten 'son', Sigurd.

Manfred Bruch claims to be a film-maker but is really a conman intent on fleecing Victor Briggs through a feigned belief in his theory; Sigurd is a young actor paid to pretend to be his son.

Victor has been (non-sexually) abusing Sym almost from her birth, imposing his own beliefs as the only possible reality, grooming her to do his bidding, maintaining control by ruthlessly dividing her from parents and peers, planning her future to suit his own ends.

Lastly, Sym has to face up to her beloved Titus being only a creature of her own imagination, a response to her desperate need (though this disillusionment at least is slightly softened at the end when it is implied he may just possibly be something more).