Dave turned back to a point where he could get up on the bridge, and his chum followed. From this point they could not see the person above them nor could he see them. When they reached the flooring of the big bridge they were less than two hundred feet from where the unknown person stood. He was leaning over the side of the structure, evidently trying to find out what had become of them. "Why, Dave, he--he--looks like you!" burst out the senator's son, as both hurried in the direction of the unknown person. "I do believe it's Ward Porton!" ejaculated our hero. He began to quicken his pace. "Yes, I'm almost sure it's Porton," he added, a few seconds later. "If it's Porton what in the world tempted him to follow you to this place?" queried Roger. "I don't know. But I do know that I'm going to capture him if it is possible to do so," answered Dave, with determination. The two chums were still almost a hundred feet from the other person when the latter glanced up suddenly and discovered them. He looked them full in the face for just an instant, and then turned and began to run away towards the opposite end of the long bridge. "It's Porton, sure enough!" burst out Roger. "Hi there, Porton! Stop!" cried Dave. "Stop, I tell you!" "You go on back!" yelled Ward Porton, in an ugly voice. "Go on back, I tell you! If you don't it will be the worse for you!" and he shook his fist at the chums. "You might as well stop," continued Dave, undaunted by the threat. "You can't get away from us. If you try to jump off the unfinished end of the bridge you'll break your neck." "If you fellows don't go back I'll shoot," returned the fellow who resembled Dave. "Stop right where you are! Don't dare to come a step closer!" "Oh, Dave! do you suppose he is armed?" questioned Roger, hastily and in a low tone. "Maybe he is. But I am going to keep on after him until he shows his pistol," was the rapid reply. "You need not come if you don't want to. I'm going to capture him and make him give up the Basswood fortune." "If you are going after him, so am I," returned the senator's son, sturdily. "Maybe it was only a bluff about shooting after all." While running along the bridge Dave's eyes fell on a short steel bar left there by one of the workmen. He stopped just long enough to pick the bar up, and then went after Porton with all the speed at his command. It was a perilous chase, for in many places the flooring of the big bridge was still missing and they had to leap from girder to girder of the steel structure. "Stop, I tell you!" yelled Ward Porton once more, when Dave was within ten yards of him. And then he turned squarely around and our hero and Roger saw the glint of a pistol as the rascal pointed it toward them. "He is armed!" cried Roger, and now there was a note of fear in his voice, and not without reason.