CHAPTER XXI.

  OFF ON A SEA TRAIL.

  As minutes and then hours elapsed and Rob did not return, Merritt becamefirst anxious, and then seriously alarmed. He knew Rob's daring nature,and had a keen fear that it might have led him into doing somethingreckless.

  It was almost dawn when he at length determined to return to theencampment and seek out Ensign Hargreaves. By the time he had trampedback over the sandy dunes day was breaking, and in the camp of the BoyScouts the notes of the morning bugle were ringing out cheerily. Thefirst of the Scouts to note Merritt's return was Donald Grant.

  He came running toward him, and then stopped short as he noted theother's drawn, tired face.

  "Why, what in the world's the matter with you, Merry?" he gasped out."You look as if you'd been drawn through a knothole. Where's Rob? Wherehave you been all night?"

  "I'll explain that later," said Merritt wearily; "just now I've got tofind Ensign Hargreaves. Rob's either been kidnapped or lost."

  He hastened on, leaving the other lad rooted to the spot with amazementand alarm. He knew Merritt well enough already to realize that the otherwas not the sort of lad to overrate a situation. If Merritt was asscared and weary as he looked, something serious indeed must have takenplace.

  In the meantime Merritt hastened to Ensign Hargreaves' tent. Hastilyarousing him, he hurriedly explained the whole matter. The officer wasout of his cot in an instant.

  "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 asoldier, 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 thatwe did wrong in not notifying you."

  The ensign's hand fell on the lad's shoulder. Then kindly enough hesaid:

  "Well, acknowledging that you did wrong is a manly thing, my boy, andwe'll say no more about the matter. But about Rob, something must bedone right away. Arouse Mr. Barr while I am dressing and we'll set aboutsearching for him at once. There's little doubt in my mind but that heis 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 whilethe 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 therascals at once."

  By the time the ensign was dressed, Mr. Barr was also attired, and thetwo immediately began a discussion of plans for the rescue of Rob. Butfirst the ensign wanted to know about Barton.

  It was hard for Mr. Barr to believe that the man whom he trustedimplicitly could have proved traitor to him.

  "The best way to find that out is to look at your papers and models andsee if anything is missing," was the response.

  "I'll do so; but I'm sure the boys must be mistaken in Barton. He hasworked 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 thatsomething is missing."

  Mr. Barr hastened off toward the shed, but returned before long with acountenance 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 theyhave done an excellent piece of scouting work. But now let us hurry offin 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 muchwater."

  "Can we all go along?"

  "No, we'll take one of my sailors, your chum Donald, Tubby Hopkins, youand myself. We haven't settled accounts with Barton yet, and I don'twant 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 therival power that is working against us can construct its submarinesfirst."

  "But you are going to make him confess?"

  "If he will, yes. If not, he faces a long prison term, although it willbe hard to prove that he actually stole the papers and models."

  "But we saw him answering those signals, and then again, last night wesaw him meet the men."

  "I'm afraid that wouldn't make very good evidence in a court of law,"was the rejoinder. "But enough of this now. Tell Hawkins (one of thesailors) to get the boat ready, and hurry through your breakfast We'llstart right afterward."

  "We can't start too quick for me," was the brisk reply. "Poor old Rob, Iwonder what has happened to him."

  While he ate a hasty meal Merritt outlined to the other Scouts what hadhappened. Following this, Ensign Hargreaves announced a change of hisplans. He had decided, he said, to take Barton along, not caring toleave the man on the island.

  "He is clever and dangerous," he said, "and I want him under my eye tillI have decided how to dispose of his case."

  "You are not going to let him know you suspect him?" asked Merritt.

  "For the present, no. As to what I shall do in the future, I have notyet made up my mind."

  Ten minutes later a black motor boat shot out of the little inlet inwhich she had been moored. As she sped seaward, making for the otherisland, those left behind set up the cry of the Eagle and Wolf patrols.

  Barton, looking sullen and suspicious, was at the engines. He knew theobject of the trip, but, of course, had no knowledge that his part init was suspected. Nor did any of the party show him by looks or wordsthat so much as a breath of suspicion attached to him. This was by theorders of Ensign Hargreaves, who had determined to give the fellowplenty of rope.

  As the _Viper_, as the black motor boat was called, raced over thewater, Merritt found himself gloomily contemplating the future. Ifanything serious had happened to Rob, he felt that he would be in ameasure responsible for allowing the young leader of the Eagles to gooff alone.