There was little enough about Sam Walden's daily life to show that he was the greatest scientist of the earth, and the sole hope for the world in the amazing battle that was brewing. His simple philosophy had changed him far from the energetic young inventor of the hydrodyne. No one would have suspected the qualities of supreme heroism that he revealed. During the days of my youth we had restlessly wandered over the globe. We had lived rather aimlessly--for the simple joy of living. The mountains, the desert, and the sea have always had a fascinating call for both of us, and we wandered in answer to that call--and during some of those years, I traveled on a strange quest of my own. But it was a whole decade since we had left our rustic home. And as our latter years had been quiet and tranquil, so the world had lost the fierce energy and struggle for advancement, that had driven it during Sam's younger days. It had settled down to the enjoyment of peaceful content. Science had turned from the invention of new machines to the improvement of those in existence, and had died with their perfection, until, when the crisis came, Sam was the only man on earth able to understand and to cope with it! The industrial organization had been perfected. Work was done by machines. Men attended them for short hours and played through long ones. There were no rich, and no poor. The products of industry were fairly divided. All men received their shares in content and enjoyed them to the full, without troubling themselves about the question of science or religion or of life that had received the attention of the past generation. And upon the peaceful tranquillity of that happy, prosperous age, there fell with no warning the lurid doom that no man could explain, throwing it into frenzied confusion. In the past era, there would have been a thousand men to attack the problem, with all the power of clear, dynamic minds. Now, there was just _one man_ who could understand! It was not so much that scientific knowledge was lacking. Men still studied and talked the language of science. The machines demanded it. But there were none of trained and penetrating minds, used to departing boldly from the world of the known to bring forth the new. Science was no longer living. It was mechanical. CHAPTER II The Radio Girl I have said that I am a dreamer, living more truly in my fancy than in the world. Perhaps my imagination is abnormally developed. Always I have had new worlds awaiting me in my dreams, to which I could retire when life was dull or unattractive. My visions have always had a singular reality, such a definite concreteness, that it sometimes seemed to be the truth.