Who might he be?

… The Underground Man at Age 50 - by Ted Gioia. (Hat tip, Dave Lull.)

Macdonald was obsessed with Freudian psychology.  Around the same time The Underground Man was published, Macdonald told Newsweek magazine: “Freud was one of the two or three greatest influences on me. He made myth into psychiatry, and I've been trying to turn it back into myth again in my own small way.”  Given this predisposition, I can’t help seeing the ‘underground man’ as a canny reference to those unconscious and troubling aspects of the human psyche that are deeply buried, not in soil but in the recesses of our minds, and come back to the surface under prodding or in a crisis.