A blow on the side of the jaw caused the Iron Boy's head to droop to one side. One more swift blow, and he dropped limply from the arms of his adversary. With a growl of triumph the man started to swim away. Steve drifted a few yards struggling manfully to regain his senses, which he did in a measure a few seconds later, though his body seemed to be numb from head to feet. The lad managed to get his hands over the edge of the small boat as he drifted alongside of it. Off on the river he could hear the fellow splashing toward shore. "Help!" shouted Steve. "Catch him!" He hoped some one might hear his voice and capture the escaping man. As it chanced some one was on shore, and that some one was Bob Jarvis, who, learning at the house that Steve had gone down to the works, followed on. He was standing there when Steve called, and he was on the bank peering down when the man came splashing ashore and started to run away. Bob grabbed the fellow by the collar. "Hold on, old man, what's doing around here! What----" The stranger launched a blow at Jarvis, whereupon Bob knocked the man flat on his back. "Police!" shouted the boy. Three Iron and Steel Police came running to the scene. "Take this man into custody! He's been up to some deviltry. Hello, I should say so. It's that fiend, Kalinski. I'll make a charge against him after I find what he has been up to." Shaking Kalinski, Jarvis demanded to know if he had seen Rush, but the Pole would not answer a word. Bob got a boat and hurried out to the abutment after seeing Kalinski safely in the hands of the police. As Jarvis neared the abutment, calling out the name of his companion, he heard Steve's faint answer. "I knew it, I _knew_ it!" fairly shouted Bob. "That scoundrel has been doing Steve up! Oh, I ought to have wrung his neck while I had the chance!" Rush was quickly taken ashore; and, accompanied by Bob, went to the police station and made the charge against Kalinski. The engineer was routed out, and an examination was quickly made of the foundation. It was found that Kalinski had partially sawed in two, half of the uprights that held the framework, so that, with additional weight upon it, the structure would have collapsed. The men were called out at once. There was no sleep for the Iron Boys that night. By daylight the work had been shored up and made safe for the time being. The boys were highly complimented for their vigilance, though by some miscarriage of justice, Kalinski got off scott-free and quickly disappeared from the mills. As for the contract, Steve Rush and Bob Jarvis pushed it along with renewed vigor. By this time the men had come to like their young overseers and all worked at high pressure. The result was that the contract was finished some days before the time named by the officials, and Steve, proud and happy, had the pleasure of seeing the plan that was the product of his own brain put into successful operation.