"Well, that incident is typical of the other three. Banks in various parts of the country have been sending rather large sums of money through the mails to their correspondents here. There's nothing unusual in that at this time of the year. But within the past five or six weeks there have been four packages--or, rather, large envelopes--of money which have failed to be accounted for. They ranged all the way from ten thousand dollars, the first loss, to the fifty thousand dollars which disappeared within the past few days. I purposely delayed wiring Washington until we could make a thorough search of the whole place, going over the registry room with a fine-tooth comb--" "Thus warning every man in it that he was under suspicion," muttered Allison. "What was that?" Rogers inquired. "Nothing--nothing at all. Just talking to myself. Far from a good habit, but don't mind it. I've got some queer ones. You didn't find anything, of course?" "In the building? No, not a thing. But I thought it best to make a thorough clean-up here before I bothered Washington with a report." "What about the men who've been working on the case up to this time?" "Not one of them has been able to turn up anything that could be dignified by the term clue, as I believe you detectives call it." "Yes, that's the right word," agreed the operative. "At least all members of the Detective-Story-Writers' Union employ it frequently enough to make it fit the case. What lines have Boyd and the other men here been following?" "At my suggestion they made a careful examination into the private lives of all employees of the post-office, including myself," Rogers answered, a bit pompously. "I did not intend to evade the slightest responsibility in the matter, so I turned over my bankbook, the key to my safe-deposit vault and even allowed them to search my house from cellar to garret." "Was this procedure followed with respect to all the other employees in the building?" "No, only one or two of the highest--personal friends of mine whom I could trust to keep silent. I didn't care to swear out search warrants for the residences of all the people who work here, and that's what it would have meant if they had raised any objection. In their cases the investigation was confined to inquiries concerning their expenditures in the neighborhood, unexpected prosperity, and the like." "With what result?" "None at all. From all appearances there isn't a soul in this building who has had ten cents more during the past six weeks than he possessed in any like period for two years back." "Did Boyd or any of the other department operatives ask to see the plans of the post office?" inquired Allison, taking another tack. "The what?" "The plans of the post-office--the blue print prepared at the time that the building was erected." "No. Why should they?"