"I thought they might have been interested in it, that's all," was Allison's answer, but anyone who knew him would have noted that his tone was just a trifle too nonchalant to be entirely truthful. "By the way," added the operative, "might I see it?" "The blue print?" "Yes. You will probably find it in the safe. If you'll have some one look it up, I'll be back in half an hour to examine it," said Allison. "Meanwhile, I'll talk to Boyd and the other men already on the ground and see if I can dig anything out of what they've discovered." But Boyd and his associates were just as relieved as Rogers had been to find that the case had been placed in Allison's hands. Four weeks and more of steady work had left them precisely where they had commenced--"several miles back of that point," as one of them admitted, "for three more stunts have been pulled off right under our eyes." The personal as well as the official record of every man and woman in the Columbus post office had been gone over with a microscope, without the slightest result. If the germ of dishonesty was present, it was certainly well hidden. "We'll try another and more powerful lens," Allison stated, as he turned back to the postmaster's private office. "By the way, Boyd, have you or any of your men been in the Service more than four years?" "No, I don't think any of us has. What has that got to do with it?" "Not a thing in the world, as far as your ability is concerned, but there is one point that every one of you overlooked--because you never heard of it. I'm going to try it out myself now and I'll let you know what develops." With that Allison turned and sauntered back into Rogers's office. There, spread upon the desk, was the missing blue print, creased and dusty from disuse. "First time you ever saw this, eh?" Allison inquired of the postmaster. "The first time I even knew it was there," admitted that official. "How'd you know where to find it?" "I didn't--but there's an ironclad rule of the department that plans of this nature are to be kept under lock and key for just such emergencies as this. But I guess your predecessor was too busy to worry you with details." Rogers grunted. It was an open secret that the postmaster who had preceded him had not been any too friendly to his successor. Allison did not pursue the subject but spread the plan upon an unoccupied table so that he could examine it with care. "If you'll be good enough to lock that door, Postmaster," he directed, "I'll show you something else about your building that you didn't know. But I don't want anybody else coming in while we're discussing it." Puzzled, but feeling that the government detective ought to be allowed to handle things in his own way, Rogers turned the key in the lock and came over to the table where Allison stood. "Do you see that little square marked with a white star and the letter 'L'?" asked Elmer. "Yes, what is it?" "What is this large room next to it?" countered the operative.