The Circular Staircase by Mary Roberts Rinehart

The bitterness toward the dead president of the Traders' Bank seemed to grow with time. Never popular, his memory was execrated by people who had lost nothing, but who were filled with disgust by constantly hearing new stories of the man's grasping avarice. The Traders' had been a favorite bank for small tradespeople, and in its savings department it had solicited the smallest deposits. People who had thought to be self-supporting to the last found themselves confronting the poorhouse, their two or three hundred dollar savings wiped away. All bank failures have this element, however, and the directors were trying to promise twenty percent on deposits.

But, like everything else those days, the bank failure was almost forgotten by Gertrude and myself. We did not mention Jack Bailey: I had found nothing to change my impression of his guilt, and Gertrude knew how I felt. As for the murder of the bank president's son, I was of two minds. One day I thought Gertrude knew or at least suspected that Jack had done it; the next I feared that it had been Gertrude herself, that night alone on the circular staircase. And then the mother of Lucien Wallace would obtrude herself, and an almost equally good case might be made against her. There were times, of course, when I was disposed to throw all those suspicions aside, and fix definitely on the unknown, whoever that might be.