"What are you doing on this bridge?" "I been across the river to see my brother." "Why didn't you take the passenger's bridge then, instead of this?" "This one is shorter for me." "Oh, no, it isn't," said Harold quickly. "The other one takes you right into Elm Street." The man offered no comment. "Why did you bend over down there a minute ago?" Harold asked. No answer was forthcoming. "Answer my question," ordered Harold curtly. The man shifted uneasily from one foot to the other. "My shoe lace came undone," he muttered finally. All the time he was talking he kept looking behind him and over the route he had just come. He seemed to be intensely nervous about something. Harold looked at him up and down from head to foot, as best he could in the poor light. He appeared undecided as to what he should do. "You'd better come along with me," he said finally. "I guess the captain might like to talk to you for a few minutes." "Where is the captain?" demanded the man. "That's nothing to you," said Harold. "You do as you're told. You walk on ahead of me and don't try any funny business; I'll be right behind you and my gun is loaded." "Which way?" the prisoner asked. "That way," directed Harold, indicating the High Ridge end of the bridge with the point of his bayonet. "As long as you live in High Ridge I'll see you part way home," he added drily. "Yes, sir," exclaimed the man, it seemed almost joyously. He set out immediately, Harold following close at his heels. "You two better go home," Harold called to Bob and Hugh as he walked off down the track. "All right," called Bob, and then he turned to his friend. "We'll take our time," he announced. "Sure," agreed Hugh. "Who do you think that man was?" "I don't know, but he did act sort of queer I thought. Probably Harold was wise to arrest him." "What'll they do with him?" "Oh, lock him up probably," said Bob carelessly. "I guess some officer will question him and if he's all right he'll be let go; otherwise I don't know what will happen to him." "How about the canoe?" suggested Hugh. "You mean, shall we go on to the boathouse?" "Yes." "The other end of the bridge is probably guarded too," said Bob. "We would be held up there and maybe be arrested ourselves." He peered earnestly down the track which led over the bridge to Rivertown on the opposite bank. Suddenly he started violently and clutched Hugh by the arm. "What's that?" he gasped in a terror-stricken voice. CHAPTER VI HUGH HAS AN IDEA "What's what?" demanded Hugh, peering in the direction Bob indicated. "Look!" cried Bob. "I am looking. What is it?" The tone of his friend's voice had alarmed him greatly, though he did not know what it was that Bob saw. "Can't you see? Right down there!" "Where? Where?" pleaded Hugh. "Tell me, Bob." "Down under the track. I see sparks." "It's a bomb," cried Hugh suddenly catching sight of the little flashes of light. "It's a bomb that man planted there."