Here's another quick thought about the movie:
The entire movie takes place inside either the Lone Man character or some other character's head. The mission is to kill the violent, closed, maybe money & power obsessed aspect of the self. The mission is to be accomplished by the use of art, science, philosophy, discipline, sex or appreciation of the beauty of the body, etc. Ultimately the Closed Side of the self is heavily guarded, inside a bunker. The Open Side of the self gets in & accomplishes its mission by using the imagination (when the Lone Man is questioned by his target as to how he penetrated the bunker, Lone Man says he used his imagination). Or, by using our imagination - making art, exploring science, etc., we may be able to get the more destructive & selfish aspects of ourselves under control.
Of course, check out the film for yourself (if you haven't yet) & see if this take on it makes sense.