You unlock this door with the key of imagination. Beyond it is another dimension - a dimension of sound, a dimension of sight, a dimension of mind. You're moving into a land of both shadow and substance, of things and ideas. You've just crossed over into the Twilight Zone.
The tools of conquest do not necessarily come with bombs and explosions and fallout. There are weapons that are simply thoughts, attitudes, prejudices, to be found only in the minds of men. For the record, prejudices can kill and suspicion can destroy, and a thoughtless, frightened search for a scapegoat has a fallout all of its own - for the children, and the children yet unborn. And the pity of it is that these things cannot be confined to the Twilight Zone.