All you must do is get to know the focus of your investigation – be they the victim or the suspect – well enough to understand how they spent their days. The time they customarily rose from their beds, what they ate for breakfast, the route they took to work. For we humans are ritualized creatures. We tend to live in certain ways, day after day and year after year, and once a detective begins to understand each individual’s chosen modes of behavior, he can also see where the pattern deviated. Why did the suspect awaken at six and not at seven? Skip his breakfast tea or forget his morning paper? What made the carriage turn toward the hills and not the harbor? Why was the locked door suddenly open or the barking dog silent? For it is in the deviation of the pattern that the answer always lies. Trevor had decreed one question to be at the heart of all good police work: What made this one particular day different from all the others?
