Chess

My dreadful situation forced me ... to try splitting myself into a Black self and a White self, to keep from being crushed by the terrible void around me

A prisoner of the Nazis for years, what if your only stimulation was imagining games of chess against yourself, second-guessing your increasingly obsessed and divided brain? Then, decades later, you can play the World Champion, but might it return you to the edge of madness ... and tip you over?