Mary Roberts Rinehart 
The Door 

But my thinking is cloudy and chaotic. The house is too quiet. I miss Judy, busy now with affairs of her own, and perhaps I miss the excitement of the past few months. It is difficult to take an interest in beef croquettes for luncheon out of last night’s roast when one’s mind is definitely turned on crime. For that is what I am thinking about, crime; and major crime at that.

I am thinking about murder. What is the ultimate impulse which drives the murderer to his kill? Not the motives. One can understand motives. It is at least conceivable that a man may kill out of violent passion, or out of fear, or jealousy or revenge. Then too there are the murders by abnormals, drug addicts or mental deficients; they have their motives too, of course, although they may lie hidden in distorted minds. And as in our case, a series of crimes where the motive was hidden but perfectly real, and where extraordinary precautions had been taken against discovery.