Jack Scott, the detective, had won fame for his agency by his masterly work in solving the problems of many skilful jewel robberies among the wealthy residents of the metropolis. He yet lacked some years of thirty, but his reputation was already of the highest among those who knew what his occupation was. For, as a matter of fact, the young man was of old Knickerbocker stock, and the inheritor of wealth. He had a genius for detective work and a love of the calling that compelled him to make it his vocation. But his employment in this wise was known only to the head of the agency with which he had associated himself, and to a few trusted intimates. The better to guard his secret he adopted the plebeian alias of Jack Scott for professional purposes instead of his own aristocratic name. He had first won the admiring attention of the detective agency's chief by an exploit when he was only eighteen years of age. At that time his mother was robbed of a fabulously valuable pearl necklace. Extraordinary rewards were offered for its recovery, and detectives big and small hunted high and low for the gems. They failed utterly in their search. But the lad worked out a theory as to the theft, gained evidence to prove it the truth--in short, within a fortnight, he had recovered the pearls, and the thieves were safely lodged in jail. Already at this early age, the boy was profoundly interested in uplift work among criminals. When his mother smilingly turned over to him the reward she had offered for the recovery of her necklace, he devoted the whole sum to this charitable work. And ever since he had made a like disposal of the proceeds from his professional services. Now, Roy recognized in the detective assigned to him by the agency, an acquaintance of his own, Arthur Van Dusen. He expressed his astonishment at this revelation concerning one whom he had regarded merely as a social butterfly. But explanations were soon made, and Roy could not doubt Van Dusen's ability since it was guaranteed by the agency. He immediately made known his need of help. "I'm afraid," he began with a tremor of anxiety in his voice, "that you have been assigned to a case which will prove hard to solve. The woman I love--the woman I had expected to marry soon--has been taken from me in a most mysterious way. Somehow she's been kidnapped, and taken to sea a prisoner on her father's yacht." "Her name?" Van Dusen demanded crisply as the speaker paused. "It's Ethel Marion," Roy answered huskily. "The daughter of Colonel Stephen Marion, who, at present, is with his regiment on the Mexican Border." He drew Ethel's message from his pocket and extended it to the detective.