"You see I haven't made any formal application yet. Of course, if it came to a question of a lawsuit, I might beat them out. But I have no money to hire lawyers, and they have. The only thing for me to do is to get that model back before they have a chance to use it to make drawings from. And how to do it I don't know." "Do you know who that messenger boy was?" asked Alice suddenly of the machinist. "I never saw him before, Miss--no. He came in a taxicab." "A taxicab!" cried Russ, excitedly. "You didn't say that before. Did you happen to notice the number?" If ever Russ Dalwood was thankful it was then, and the cause of it was that Mr. Burton had a mathematical mind in which figures seemed to sprout by second nature. "I did notice the number," he said. "It isn't often that taxicabs stop out in front here, and I looked from my window as one drew up at the curb. I was working on your patent at the time. I saw the number of the cab, later, as the messenger boy rode off in it with the model." "What was it?" asked Russ, preparing to make a note. The machinist gave it to him. "Now if we can only trace it!" exclaimed the young inventor. "I guess I can help you out, friend," broke in their own taxicab chauffeur. "I've got a list of all the cabs in New York, and the companies that run them." Rapidly he consulted a notebook, and soon had the desired information. The office of the company was not far away, and Russ and the girls were soon speeding toward it. What the next move was to be no one could say. The manager remembered the call that had come in. Two men had come with a messenger boy to engage a cab to go to the address of the machine shop. "And who were the two men?" asked Russ. The manager described one whom Ruth and Alice had no difficulty in recognizing as Simp Wolley. "The other man was shorter and not so well dressed," the cab manager went on. "Bud Brisket!" exclaimed Russ. "I know him. Now the question is: Where did they take my model?" "There I'm afraid I can't help you," said the manager. "Wait!" exclaimed Alice. "Did you happen to notice the number on the messenger boy's cap?" "No, I did not, I'm sorry to say," the man answered. "Then that clue is no good," spoke Russ, with a sigh. "It might be," put in Ruth. "The messenger was probably engaged from the office nearest here. We could find that and make some inquiries." "So we could!" cried Alice. "Oh, Ruth, you're a dear!" Russ looked as though he would have said the same thing had he dared. An inquiry over the telephone to the main office of the messenger service, brought the desired information. And soon, in their taxicab Russ, Ruth and Alice were at the sub-station. There the identity of the messenger was soon learned, and he was sent for. "Sure, I went to de machine shop," admitted the snub-nosed, freckled-faced lad. "I got some sort of a thing. I didn't know what it was." "And where did you take it?" asked Russ eagerly.