"You had no business to go off alone like that without notifying me," he exclaimed rather sharply. "Don't you know that the first duty of a soldier, a sailor or a scout is to obey orders?" Merritt crimsoned and hung his head. He knew that the officer was right. "We thought we were doing a good thing," he said, "but I know now that we did wrong in not notifying you." The ensign's hand fell on the lad's shoulder. Then kindly enough he said: "Well, acknowledging that you did wrong is a manly thing, my boy, and we'll say no more about the matter. But about Rob, something must be done right away. Arouse Mr. Barr while I am dressing and we'll set about searching for him at once. There's little doubt in my mind but that he is on that island where you saw the signals flying." "But how could he get there unless he had an airship?" inquired Merritt. "Hasn't it occurred to you that he might have hidden in the boat while the men were out of it?" "Gracious! In that case he may be their prisoner by this time!" "I am afraid that there is little doubt of that. We must get after the rascals at once." By the time the ensign was dressed, Mr. Barr was also attired, and the two immediately began a discussion of plans for the rescue of Rob. But first the ensign wanted to know about Barton. It was hard for Mr. Barr to believe that the man whom he trusted implicitly could have proved traitor to him. "The best way to find that out is to look at your papers and models and see if anything is missing," was the response. "I'll do so; but I'm sure the boys must be mistaken in Barton. He has worked for me for many years." "Possibly the large price he was offered to turn over the plans of the _Peacemaker_ had something to do with it," suggested Merritt. "Perhaps; but I'll not say anything till I find out definitely that something is missing." Mr. Barr hastened off toward the shed, but returned before long with a countenance filled with apprehension. "My most important blue prints and models are missing!" he exclaimed. The ensign made a dry grimace. "Our young friends were right," he said. "In detecting the rascal they have done an excellent piece of scouting work. But now let us hurry off in search of Rob at once." "How will you reach that other island?" asked Merritt. "We will go in the motor boat. She is fast and does not draw much water." "Can we all go along?" "No, we'll take one of my sailors, your chum Donald, Tubby Hopkins, you and myself. We haven't settled accounts with Barton yet, and I don't want him left practically alone on the island." "Do you think he would try to harm the submarine?" "I think it likely. He has probably been paid to injure it so that the rival power that is working against us can construct its submarines first." "But you are going to make him confess?" "If he will, yes. If not, he faces a long prison term, although it will be hard to prove that he actually stole the papers and models."