It was fully light when they went down into the yard where the small auto had been left. And suddenly the silence of the dawn, made musical by the twitterings of the birds, was broken by an increasing roar and throbbing noise. “Airship!” grunted Koku. “Suah enough!” exclaimed Eradicate, pointing up. “Dere she am!” The throbbing sound became louder, and a moment later they saw the plane, a large one, approaching from the west. “It’s Mr. Damon’s machine!” cried Ned. “What in the world is he flying so early for? He isn’t sure enough of himself to take that big plane out alone—he only got it the other day. Great Scott! Look! He’s going to hit your mooring mast!” At one end of the big landing field outside the fence Tom had recently erected a tall steel mast, to which he moored a small dirigible balloon with which he was conducting experiments. As all looked up they saw Mr. Damon in his new machine headed straight for this mast. “He doesn’t know it’s there!” cried Ned. “He’s sure going to hit!” A moment later there was an alarming crash, and the top of the mast was seen to break off while one edge of the aeroplane’s left wing crumpled. CHAPTER VI AGAIN A PRISONER The threat which Tom Swift heard the men in the pursuing motor boat mutter—a threat to catch him at any cost—was not needed to cause him to speed up the craft he had appropriated in an endeavor to escape. The sinister character of the men who wore the masks he could easily guess at. As to the others, he had begun to suspect them soon after they obtained work in his plant. Though they were clever mechanics, Tom did not like Kenny and Schlump and so had directed their discharge. “They either have it in for me on that account,” mused Tom, as he made an adjustment to the motor to get more speed, “or else there’s something deeper in the plot. I guess they must have chained me up after I blundered into their tunnel. I’d like to know what all this means, but now is not the time to stop and find out. I must get away and ask questions afterward.” It was to be a desperate chase—Tom Swift realized that from the tense and eager manner of the men in the boat now plowing through the waters of Lake Carlopa. They were forcing their craft to her best speed in an endeavor to overtake him. “It’s a wonder they don’t begin shooting,” mused Tom. “A crowd of men like that, with two of them masked, won’t stop at shooting. Maybe I’d better get down a bit.” He had been standing up in the boat, the better to make adjustments to the motor, but now, as he thought of the possibility of being fired upon, he crouched down to give less of a target to the men. This move of his seemed to be misinterpreted by the pursuers, for one of them cried: “There he goes overboard! One of you take after him!” This was shouted by one of the masked men, whose identity Tom Swift could only guess at, though he judged all of them to be some of his enemies.