The principal of a detective agency, from his long experience with criminals, learns the earmarks of different classes of men, and he is often able to determine the name of the guilty party in any given robbery by the manner in which the job was done. He can readily see whether a novice in crime was engaged, and also whether any collusion existed between the parties robbed and the criminals; and so, when he sees the traces of a bold, skillful, and experienced man, he knows that it is useless to track down some insignificant sneak-thief, simply because the latter happens to have been in the vicinity. Yet, neither will he slight the smallest clue if there is a bare chance that any valuable fact may be obtained from it. But the _sine qua non_ is that he, and he alone, shall direct the whole affair. A divided responsibility simply doubles the criminal's opportunities for escape. Among the many difficulties of the detective's work, none are more embarrassing than the early development of false clues. In the stories heretofore published, the direct steps leading to the detection and arrest of the criminals have been related, without referring to the innumerable other investigations, which were progressing simultaneously, and which, though involving the expenditure of much thought, time, and money, proved after all to be of no value whatever in developing any evidence in the case. In this operation, such instances were of frequent occurrence, and I propose to mention a few of them to show how wide is the range of the detective's inquiries, and also the annoying delays to which he is often subjected by the inconsiderate zeal and interference of outside parties. These latter may be--indeed, they generally are--well meaning people, anxious to serve the cause of justice; though, on the other hand, they are sometimes spiteful meddlers, striving to fix suspicion upon some personal enemy. The plan of detection which alone can insure success, must be one which neither forgets nor neglects anything. In investigating any alleged crime, the first questions to be considered are: 1. Has any crime been perpetrated, and, if so, what? 2. What was the object sought thereby? The matter of time, place, and means employed must then be carefully noted, and finally we come to consider: 1. Who are the criminals? 2. Where are they now? 3. How can they be taken?