The Sphinx presents a riddle which the traveller must solve or die.

On the surface, Sphinx tells of the arrival into a polite and fashionable 1920's rural community of one Nicholas Cabot, a young man who has recently come into money. The deeper themes of the book include levels of consciousness, the nature of choosing, and the boundary between life and death - explored chiefly through the device of Cabot's esoteric chemical experiments. Like all of Lindsay's books, Sphinx gives up its secrets a little at a time, and rewards frequent re-reading.