The watcher lost no time in following, but Rush kept at a safe distance, dodging when he had to pass an electric light, now and then throwing himself beside the track flat in the mud and water of the gutter when he thought Klink was about to look back. In this way he avoided discovery. Klink continued on until he neared the pump station, when he slackened his pace. Fortunately for Steve, there were no lights in that part of the level, so that he had little difficulty in keeping out of sight. Klink kept on walking until nearly opposite the pump station, when he suddenly disappeared. For a moment Rush was puzzled; then he discovered that his man had stepped in between two posts that held up the lagging at the side of the tunnel. The boy's eyes gleamed. "Now, my fine gentleman, we'll find out what is going on here! I believe I have landed the man I am looking for. I----" It was just midnight, and the pump man had left his machinery to go for water to drink with his lunch. Steve understood this, and evidently the man who was pressed close up against the lagging did also, for he quickly stepped out, glanced about him, then ran to the square opening cut in the rocks in which the pump machinery was located. Rush ran up on tiptoe to within about twenty yards of the pump station. He was watching Klink narrowly. The latter snatched something from inside his coat, thrusting the object under the plunger of the largest of the pumps. Next came something long, slender and white that looked like a large string. Almost holding his breath, Steve crept nearer. "He is attaching a fuse. That was dynamite that he put under the plunger. He's going to blow up the pumps and flood the mine!" Klink struck a match and applied it to the end of the fuse. It was now Steve Rush's time to act. Seconds were precious. The boy seemed scarcely to touch the ground as he sprinted forward. He was upon the man before Klink saw him. One swift kick from Steve's heavy boot toppled the man over on his side. The Iron Boy snatched the burning fuse from the stick of dynamite and hurled it from him. By that time Klink was on his feet. With blazing eyes he rushed at the boy. Steve believed, and with good reason, that Klink intended to murder him. But the boy stood calmly awaiting the onslaught. The man was large and powerful, but this did not daunt the plucky lad. Klink was now more than three feet from him when, suddenly, Steve's right foot flew out, catching the fellow fairly in the pit of the stomach. The man uttered an exclamation, at the same time pressing both hands to the spot where the heavy boot had landed. Rush fairly leaped into the air, his fist catching Klink directly between the eyes. Klink toppled over backwards, and Rush, having lost his balance, fell prone on top of him. The fellow's arms and legs instantly clasped the boy in a tight embrace. But in that one close look into the fellow's eyes, Steve had recognized him.