“Say, it couldn’t be that some animal gnawing, a rat maybe, fooled you bad, I suppose, Frank?” suggested the doubting Jerry. “How about that, Will?” asked the one addressed, turning to his chum. “Oh! I heard it as plain as anything,” Will hastened to declare, vehemently; “and just as Frank said, it must have been somebody trying to open the door. First I thought of panthers and alligators and all those things; but now I just know it must have been a man, because he turned the knob of the door, and even shook it a little as if he might be angry because it was fast.” “Listen to the nerve of that!” exclaimed Bluff. “Thinkin’ we expected to keep open house on this trip. Tried the door, did he? Wanted to come in and join the Outdoor Chums! Perhaps if we’d left that door unfastened we’d have waked up in the morning to find a tramp sleeping on the floor of the cabin.” “What is it, Frank?” asked the nervous Will, upon seeing the other start forward. For answer Frank stooped down, and seemed to pick some object from the deck, just where the gunwale of the boat cast a little shadow. “This doesn’t belong to anybody here, I reckon?” he remarked, holding aloft the object he had found. “A hat, and an old slouch one at that!” exclaimed Will. “I pass!” remarked Bluff, immediately. “Give me the go-by, Frank; never saw it before now!” called out Jerry, after he had taken one good look at the head covering, which differed in every way from such hats as the boys carried along with them. “And,” Frank went on to say, “as it certainly wasn’t here when we went to bed, we can set it down as pretty sure the fellow who crept aboard the _Pot Luck_ while we were asleep dropped it, when he had to cut and run so lively after my shot.” “That goes,” observed Jerry, with conviction in his voice; for he evidently was in agreement with all that Frank said. “Looks to me like a tramp’s hat,” remarked Will, as he bent closer to examine. “But see here, Frank, there’s some marks inside; aren’t there?” “Letters, too,” echoed Jerry, crowding closer. Frank held up the hat so that the light from his torch would cover the inside; and there, sure enough, the boys discovered three letters fastened to the crown of the old felt head covering. They stared at them as if hardly able to believe their eyes, and there was a good reason for this, since the letters were: M. T. S. “My goodness!” ejaculated Will, he being the first to recover his breath; and what he said seemed to voice the sentiments of his chums, for they were all of one mind there; “M. T. S. it says, fellows; and don’t you see those letters stand for Marcus Stackpole, the very man Uncle Felix warned us never to let come aboard of his houseboat! And here he’s tried to break in the very first night we’re on the river! Don’t it beat everything though, what it all means?” CHAPTER VII—ANOTHER CARELESS PILOT