Like most mail aviators, Sherman held a commission in the Army Reserve and had been to West Point. It was not difficult for him to guide the great fighting machine there, to find a field gun and ammunition and load it into the fighting machine. He knew very little about artillery of any kind, but when they returned to the door of the Lassan city, he was enough of a mechanic to get the shell into the breech and find the firing mechanism. The gun went off with an earsplitting crack and the shell whistled down the valley to burst against a green hillside where they saw a graceful pine dip and fall to the shock. And just at that moment such a sense of disturbance and alarm invaded Sherman's mind as he had never felt before. He looked around; the group of Lassans who had poured out of the city to see the experiment with the gun was gathered in a tight knot, eagerly conversing with one another. The old Lassan who was conducting him turned round abruptly. "Into the fighting-machine at once," he commanded. "Our birds have sent a message that they are being attacked by some strange creature of your world." As Sherman climbed through the door of the fighting machine he glanced over his shoulder to see, far down the valley a black speck against the sky. An airplane? he wondered and it suddenly occurred to him that however great his thirst for information, he should have kept his knowledge of guns from the Lassans; for if there were other people alive out there in the world the day might come when it would be a battle--and explosives were as new to the Lassans as the light-ray to the children of men. * * * * * After that it became a struggle. Sherman found he had to be constantly on his guard; constantly he had to conceal knowledge from the probing, insistent mind-helmets. The Lassans seemed interested in only one subject now: human methods of making war, human guns, human armor, human ships. Once they brought him an encyclopedia and as he held it on his lap went over every word of the articles on military subjects, questioning and cross-questioning him. Fortunately, it was an old encyclopedia, and he knew so little about it that in most cases he was able to throw open his mind and let his opponents see that it lay empty on these subjects. And still they were not satisfied. Yet if he gave information, he also received it; for little by little an understanding of the subtle material they called pure light became part of his mental equipment.... One day, as he returned from a long session in the questioning room and his cage clicked into position behind him, he was startled by a cheery, strident voice: "Well, well, if it isn't my old pal, Herbie. How's the boy?" Sherman looked around. In the next cage was Marta Lami, grinning and extending her hand through the bars. "For Heaven's sake!" he said, and took the offered hand. "How did you get here?"