He was himself coming to some sort of conclusion in the matter, and it first of all seemed to be founded on a certain fact, which by now Frank had made certain of. Luther Snow was _not_ the real name of their passenger. Frank had made a startling discovery one day recently, and it put an end to his bewilderment at least. It happened that, chancing to notice some handkerchiefs the old man had stowed in his various pockets, and which he was washing out, after a crude fashion that would have made a woman laugh, Frank saw that in every case a name had been carefully erased with indelible ink. Then again there began to be other little things about the old man that told the observing lad he surely had never been a carpenter. Frank purposely asked him to build some boxes out of several smooth boards purchased for the purpose; and the result was a botched job that any second-class carpenter would have blushed to own. Even Bluff screwed up his eyebrows when he saw them, and privately declared that he did not wonder old Luther was out of a job so often, if that was a sample of the best he could do along the line of his trade. To Frank there was a deeper significance in this failure to make good on the part of their passenger. No wonder his hands were so free from calloused places, for Frank now felt positive that Luther had never been a carpenter in all his life. If that part was made up, then probably the entire tale was only a “fairy story,” told for a purpose. That purpose was to get aboard the houseboat, for some reason or other. Well, he had been aboard for some weeks now, and nothing had happened, only he seemed to like it so well he wanted to remain with the boys until they reached New Orleans. There was something about this desire on his part that impressed Frank. If, as he now actually began to believe, Luther Snow was really the Marcus Stackpole of whom Uncle Felix had particularly warned them, why had he not picked up the hidden treasure Jerry was always talking about, and disappeared long ago? Frank somehow began to believe that, after all, there was no secret _cache_ aboard the boat which might contain valuables in the shape of papers or jewels. Jerry liked to think there was, but really they had not a peg on which to hang such an idea; except that queer Uncle Felix seemed to want to keep strangers off the boat, and particularly a man he seemed to dislike very much, one Marcus Stackpole. Frank was even now busying himself with trying to lay some little trap by means of which he might learn the truth.