"Hurrah!" was the word that Hiram Dobbs spoke exultantly, and Dave looked at him in profound surprise. Hiram had lifted himself up from the seat. Now he went through some movements that almost startled the puzzled young aviator. Suddenly his arm shot out of the sling, and as suddenly Hiram, though with a wince, swung it around once or twice, and the three splints holding it cracked and split audibly. "Hey, Hiram!" gasped Dave. "S-sh!" uttered his assistant warningly. Hiram ran his free hand down into his pocket. He drew out the big pocket knife he carried. It was more of a tool than a whittling toy, for he used it in tinkering about the airship. With his teeth, Hiram opened its largest blade. He gave a slash at the cords surrounding his other arm and his feet. Then he leaned over towards Dave. A few deft strokes of the keen blade, and Dave, like himself, was free. "Easy," he whispered, as Dave started up. "I'll watch Dawson. You get into the pilot's seat." "Good for you, Hiram!" whispered back the young aviator, fairly thrilling with the excitement of the moment. Dave took in every detail of the mechanism before his eyes. He made sure of no faulty start. "All ready," he announced after a minute or two. "Good-bye!" spoke Hiram, with a gay bold wave of his hand in the direction of the sleeping, Dawson. "Put on the muffler," ordered Dave, as the exhaust began to sizzle. Hiram did so. It was too late, however, to avoid sounding a warning to Dawson. The big man started up with a yell. He came to his feet roaring out: "Come back!" "I hope you'll find the walking good!" shouted Hiram, waving his hand in adieu to the amazed Dawson. "Hiram, you're a genius!" cried Dave. The Drifter struck a course as true as a die. The splendid machine and the young aviator were both at their best. There was a last fading picture of a forlorn man convulsed with rage and despair. Then the two boy aeronauts turned their back on the enemies who had been hoisted by their own petard. "It's great, its grand," cheered Hiram, bubbling over with joy, as the exhilarating air and their magical progress made him realize what freedom meant to its fullest extent. "I don't understand. Your arm, Hiram?" said Dave. His jolly assistant waved the arm in question gaily. "Wasn't it hurt?" "Yes, and badly, I thought," reflected Hiram. "It was numb and useless when the half breed attended to it, but he was mistaken and so was I in thinking that any bones were broken." "They were not?" "Not a bit of it. Don't you see? It pains, and I'm bragging when I swing it around as if it was as good as ever, but I can use it." "You have used it to a grand purpose, Hiram." "I didn't notice that I could use it until they locked me up with you." "Why didn't you tell me then?" "Oh, I wanted to surprise you." "You have, Hiram." "I thought I'd play 'possum on those smart fellows. I played the cripple strong. You see what has come of it."