"But you are too interested in Wall Street to leave it for the open road?" He was sarcastic now. "Or do you fear deeds of daring? Do you want to right a great wrong? Rescue an oppressed people, overturn the tyranny of an evil monarch, and put your friend and the girl he loves upon the throne? Or do you want to go down to work as usual in the subway to-morrow morning? Are you afraid that in this process of becoming henchman to a king you may perchance get killed?" I matched his caustic tone. "Let's hear it, Derek." CHAPTER II _The Challenge of the Unknown_ Incredible! Impossible! I did not say it, though my thoughts were written on my face, no doubt. Derek said quietly, "Difficult to believe, Charlie? Yes! But it happens to be true. The girl I love is not of this world, but she lives nevertheless. I have seen her, talked with her. A slim little thing--beautiful...." He sat staring. "This is nothing supernatural, Charlie. Only the ignorant savages of our past called the unknown--the unusual--supernatural. We know better now." I said, "This girl--" He gestured. "As I told you, I have for years been working on the theory that there is another world, existing here in this same space with us. The Fourth Dimension! Call it that it you like. I have found it, proved its existence! And this girl--her name is Hope--lives in it. Let me tell you about her and her people. Shall I?" My heart was pounding so that it almost smothered me. "Yes, Derek." "She lives here, in this Space we call New York City. She and her people use this same Space at the same time that we use it. A different world from ours, existing here now with us! Unseen by us. And we are unseen by them! "A different form of matter, Charlie. As tangible to the people of the other realm as we are to our own world. Humans like ourselves." He paused, but I could find no words to fill the gap. And presently he went on: "Hope's world, co-existing here with us, is dependent upon us. They speak what we call English. They shadow us." I murmured, "Phantoms of reality." "Yes. A world very like ours. But primitive, where ours is civilized." * * * * * He paused again. His eyes were staring past me as though he could see through the walls of the cellar room into great reaches of the unknown. What a strange mixture was this Derek Mason! What a strange compound of the cold reality of the scientist and the fancy of the romantic dreamer! Yet I wonder if that is not what science is. There is no romantic lover gawping at the moon who could have more romance in his soul, or see in the moonlit eyes of his loved one more romance than the scientist finds in the wonders of his laboratory. Derek went on slowly: