He reached the other side, stood on the bank a few minutes, then began to retrace his steps. He had gone about half way from the shore to the abutment when a sound reached his ears that caused him to halt and listen--to bend over and peer down into the shadows below. "That sounds to me like a metal saw," muttered Steve. "It may be an echo from the shore, but I could almost swear it was down there somewhere about the abutment." The river was so dark that he could see nothing at all, while the structure itself was in the bright moonlight. The Iron Boy crept along a little further, then lay down on his stomach, and began wriggling his way along in that position. Reaching a point right over the abutment he placed his ear to the iron and lay listening. "Rasp, rasp, rasp!" The sounds were clearly borne to his ears. "Somebody is down there, as sure as I am alive! What can he be doing? I believe there is something going on here that I ought to know about. If I try to get down from here I shall be discovered, and there will be no chance of learning what I want to find out." After a moment's reflection Rush started back toward the shore, hugging the girder as closely as possible to avoid discovery. He reached the bank, scrambled down to the water's edge and stood peering out into the shadows. Not a sign of a human being could he make out, for the river was too wide at that point. Steve hesitated not a moment. He removed his coat, vest, shoes and shirt, binding his suspenders about his waist for a belt; then he let himself down into the water without making the slightest splash. CHAPTER XXIV CONCLUSION Instead of swimming straight for the abutment in the middle of the river, Rush headed directly up stream, keeping just a little way out from the shore. His object, at the time, was not apparent. It was a little later, when, after having swum up the river some fifteen rods, he made an abrupt turn and struck out for the centre. All this time he was swimming without making a single splash, his hands and feet being constantly under water. Rush was pretty sure that some rascality was going on, or he would not have gone to so great pains. Reaching a point directly in line with the abutment the boy turned again, this time heading down stream, floating along with the tide, making just enough movement with his hands to keep him on his course. The abutment was outlining itself in the shadows more plainly every minute, now, and Steve was straining his eyes in an effort to make out what was going on. All at once the rasping sound ceased and he saw a man straighten up and look about him. Something bright glistened in the hands of the man under the abutment trestle. Steve settled down in the water as low as he could. Then the man resumed his task. "I believe he is sawing the abutment supports down with a metal saw!" gasped the Iron Boy. "The scoundrel! He's fixing the place so it will go down when all the men get out there to-morrow."