A lost soul. An unruly subconscious. A second chance.
From the introduction:
Know Thyself is a role-playing game about an amnesiac going through his own personal hell of a fever dream or nightmare, trying to recall who he is and possibly change his fate. While this goes on, he fights against his subconscious which is working to subdue or confuse him.
One player plays the Amnesiac and the others play foils to that character, both as his subconscious and people he remembers over time.