"Really great criminals are never found out, for the simple reason that the greatest crimes-their crimes-are never discovered," remarked Professor Augustus S. F. X. Van Dusen positively. "There is genius in the perpetration of crime, Mr. Grayson, just as there must be in its detection, unless it is the shallow work of a bungler. In this latter case there have been instances where even the police have uncovered the truth. But the expert criminal, the man of genius-the professional, I may say-regards as perfect only that crime which does not and cannot be made to appear a crime at all; therefore one that can never under any circumstances involve him, or anyone else."