"Who'll believe us?" broke in Audubon gravely, and shook his head. "It won't do, Norton! Duval is too prominent a man to be smashed without clear evidence. Besides, we wouldn't break up the gang by nabbing him and Grigg alone. Depend upon it, we could do little against that clever villain without more evidence than those words. But what a blackguard he is--to be robbing his own townsmen!" "And that girl--Grigg's daughter!" broke in Norton, a flame of rage sweeping through him. "Did you hear them? He's buying the girl, Audubon--buying her! Damn it, man, did you ever see that girl?" Audubon gazed at him, astonished at the outburst. "Yes," he replied slowly, "I've seen her once or twice in the store. Do you think that's really what they meant? Why, it can't be possible, Norton!" None the less, Norton knew that the thing was true. He drew a deep breath as the full realization of his triumph broke over his mind. By a stroke of sheer luck he had solved the mystery of Blacknose--but was it luck? Had not one thing led to another in marvellous sequence--the cane-brake, the fire, the flatboat, the landing, and finally the vireo singing the song of a goldfinch? Surely, there was more than luck in all this! A new burst of rage came into his heart at thought of Kitty Grigg, however. So this evil-hoary old backwoodsman who was not her father was planning to sell her to Duval! Norton inwardly vowed that such a sale should never be consummated. He remembered the girl as he had last seen her by the cabin, glorious in her unstained beauty and her fine clear poise--and groaned. With a sudden movement he reached inside his shirt and took out the little gold eagle still pinned to it. "Audubon," he cried earnestly, "I swear by this emblem, which stands for the things I hold dearest--my country, and my father's memory--that before Duval carries through his purpose regarding Kitty Grigg, I'll do to him as I did to his servant this morning! So help me!" The bird-lover gazed at him searchingly. "Then--you know the girl?" "Know her? Yes!" exclaimed Norton hotly. "I know her, and she's no daughter of Abel Grigg! Who her real family was will not be hard to find out if I can get in touch with some of the officers of the Cincinnati--but now for work. Audubon, you heard what those devils said about a horse-boat belonging to a Captain Brookfield. Do you know anything of such a craft?" The other nodded, frowning. "Yes. Brookfield is an odd genius who has invented a way of driving his forty-ton boat by horse-power against the river-current. He is at Louisville now, taking contracts for his next trip down the river, and sails next month." "Well, see here!" Norton felt the fever gripping him again, but had already glimpsed a plan of action. "You get back to Louisville, see Elisha Ayres, and tell him about it. Ayres will communicate with me at Blue River." "And you----!" queried the astonished Audubon.