“Then all we’ve got to do,” Jimmie explained, “is to remain right here and watch our machines all night. That’s what I call a downright shame!” “We don’t have to all watch at the same time,” Ben advised. “You boys go to sleep after we get our supper and I’ll stick around until midnight. Then one of you can go on guard until four in the morning and the other watch until we get ready to leave.” “That’s about the way we’ll have to do it,” Jimmie responded, “only,” he went on, “if the fellow makes his appearance at the camp and tries any funny business, the one on watch must wake the rest of us.” This being agreed to, the boys ate a hearty supper and Jimmie and Carl crawled into a hastily set up shelter-tent and were soon sound asleep. Ben did not remain by the camp-fire after that. Instead, he took a position beyond the circle of light, from which the machines were in full view, and watched and listened for the appearance of the mysterious aviator. Directly the whirr of the motors came louder, and the boy saw the bulk of an aeroplane outlined against the field of stars above. It was quite evident that the stranger was seeking a place to land, and Ben, resolving to take the initiative, hastened out into the field swinging an electric searchlight. “Now,” he thought, “we’ll see if this fellow wants to meet us face to face, or whether he wants to sneak about in the darkness in order to work mischief to our machines.” After the boy had waved his searchlight for a moment a shout came from above, and a machine every bit as large and as finely finished as the _Louise_ came volplaning down to the field. The rubber-tired wheels had scarcely ceased revolving in the soft earth when Ben stood by the side of the machine, from which a man of about thirty years—a tall, slender man, with very blue eyes and a very blond head—was alighting. “Hello, son!” the man exclaimed, as he came up to where the boy was standing, “are you out on a trip for your health, too?” “That’s about the size of it,” answered Ben. “Where from?” was the next question asked. “New York city,” was the reply. “Good old town!” exclaimed the stranger, walking toward the fire as if inclined to make himself quite at home. “You bet it is!” answered Ben, following along close by his side and watching his every move with suspicion. The boy regretted now that he had not awakened his chums before giving the signal to the stranger. There was no knowing what the man might attempt to do. Ben did not fear physical violence for he considered himself more than a match for the intruder. But he knew that a stick of dynamite or some other destructive explosive tossed into the mechanism of the machines would render them absolutely useless. For this reason he watched the visitor closely, never taking his eyes from the rather large and ham-like hands which swung pendulously at his sides. The stranger did not appear to notice the attention he was receiving.