The last paragraph of The Secret Agent by Joseph Conrad:
And the incorruptible Professor walked, too, averting his eyes from the odious multitude of mankind. He had no future. He disdained it. He was a force. His thoughts caressed the images of ruin and destruction. He walked frail, insignificant, shabby, miserable - and terrible in the simplicity of his idea calling madness and despair to the regeneration of the world. Nobody looked at him. He passed on unsuspected and deadly, like a pest in the street full of men.