They could not find out how Greenbaum got in, and Tom began to fear there was still another spy in his working force. He resolved to have a strict inquiry next morning and made a note to charge Mr. Jackson with this. “But how did the talking-picture work, Tom?” asked Ned when they were ready to close the laboratory and disperse for the night. “Fine! Almost perfect! I’m on the verge of success!” “That’s why those plotters are getting desperate, I guess,” suggested the manager. “They’re out to do you, Tom. Better clean this thing up and sell it. Then they’ll let you alone.” “I’m thinking of that. But I want to make one more demonstration and have Mary, Helen, and some of their folks see it. There are one or two little improvements that occur to me that can be made, and then I’ll be ready for a final showing before I get my last patents. After that I’ll be ready to market my invention.” “Going to give a sort of dress rehearsal?” asked Ned, with a smile. “That’s it.” A search next morning revealed little more than had been found out the night before. Nor was the strict inquiry the superintendent conducted fruitful of results. No spies were uncovered among Tom’s factory forces. But, omitting no precautions, the young inventor took even greater pains to insure privacy in his personal laboratory. There he worked hard to perfect his invention, taking hardly any sleep for a week, so that he was almost exhausted. His father and Ned helped and so did Mr. Damon. Koku and Eradicate were kept on guard, and the giant, having satisfied his longing for fash, declared that he would not move from his chair again to pick up a dozen of the odorous melons. And, laboring hard, Tom brought to what he thought would be perfection his newest invention. Mr. Swift was greatly interested in it, though he begged his son to proceed cautiously. “You evidently have powerful enemies, Tom,” said the aged man. “They must think you will ruin part of their business in moving pictures and theatrical performances and that is why they are so anxious to get you out of the way. Be careful!” “I will,” promised the young man. “But they can’t stop me now. Success is just across the line.” He had entirely rebuilt the machine after the fire and blast, and it was larger and better than ever. Mary and Helen, with their families, had been taken into Tom’s confidence and he had promised them that they should see and hear the performance of Ned and Mr. Damon. “It’s quite thrilling!” said Mary, with a fond look at Tom. “I hope you’ll say so after the demonstration,” was his answer. “I may ask you and Helen to perform, also.” “Oh, we’ll be glad to,” said Helen. “I can’t let Ned get away with all the honors.” It was the day on which the final demonstration was to take place. Tom had arranged his apparatus and had invited the two girls and their families to come to the laboratory for the evening.