My experience as a detective has convinced me that the evident is usually true; that in a great majority of cases crime leaves a straight trail, and ambiguities are more often due to the inability of the trailer than to the cunning of the trailed. Such reputation as I have established is due to acceptance of and earnest adherence to the obvious.
In this affair of Thomas Gilbert's death, everything so far pointed one way. The body had been found in a bolted room, revolver in hand; on the wall over the mantel hung the empty holster; Worth assured me the gun was kept always loaded; and there might be motive enough for suicide in the quarrel last night between father and son.
Because of that flitting shadow I had seen, I knew this place was not impervious. Some one person, at least, could enter and leave the room easily, quickly, while its doors were locked. But that might be Hughes—or even Worth—with some reason for doing so not willingly explained, and some means not readily seen. It probably had nothing to do with Thomas Gilbert's sudden death, could not offset in my mind the conviction of Thomas Gilbert's stiffened fingers about the pistol's butt. That I made a second thorough investigation of the study interior was not because I questioned the manner of the death.
I began taking down books from the shelves at regular intervals, sounding the thick dead-wall, in search of a secreted entrance. I came on a row of volumes whose red morocco backs carried nothing but dates.
"Account books?" I asked.
Worth turned his head to look, and the bleakest thing that could be called a smile twisted his lips a little, as he said,
"My father's diaries."
"Quite a lot of them."
"Yes. He'd kept diaries for thirty years."
"But he seems to have dropped the habit. There is no 1920 book."