“Exactly. That’s the only way you can succeed in this business. You mustn’t let your identity be known. So I kept under cover. I knew that if Willie’s statement about being in the wireless room was true,—and personally I had faith in it—then some one else slipped in here while the office was apparently unoccupied, got your papers, and slipped out unobserved. That’s evident. It is also evident that whoever did it at some time most likely had your key, in order to have a false one made. Who could have had your key? If one office boy had it, another might, eh?” The Treasury Agent nodded assent. “So that pointed to young Smith here. If he had a key, he was likely crafty enough not to use it while he was still office boy, because suspicion would almost certainly fall on him. But when he had been shifted to another department, then he could use it, and if he got away unseen, suspicion would point to his successor.” “Plain as daylight,” said Mr. King. “I found that there was one other reason that might figure. Smith here has been bullying Willie. He has threatened to beat him the first time he caught him outside alone. So he evidently had hard feelings toward him. That suggested the possibility of theft for the purpose of getting Willie into trouble. I don’t believe he did it for that reason, but there was the possibility, you see.” Sheridan paused to light a cigar. “I do see,” said Mr. King. “Again, who would be better able to slip in here unobserved than some one who knew intimately the habits of everybody in the office? He knew how to approach the office so as to avoid observation, and how to get in and out by back ways, if any existed. There was every reason to believe that if Willie Brown didn’t take the papers, Tom Smith did. So I went after Tom Smith.” “How did you get him?” “Well, I cleaned spittoons and mopped floors and washed woodwork, and nobody paid any more attention to me than they do to any other scrub men. As a cleaner I could be in the offices after the clerical forces went home. Then I searched. It took me a long time to find that wax. But finally I found it tucked away in a crack far up on the under side of Smith’s desk. Only the most thorough search would have revealed it. When I found the wax I was confident I was on the right trail. When you gave me a duplicate impression in the wax, I knew I was right. The thing that remained was to find the key.” “How did you ever do it?”