Circumstantial evidence

Detection, or even the sniff of a murder, is postponed during the first eleven chapters. Instead we read of the ingenious scheme of a disgruntled chemist shop worker to produce and market a medicine that can be "almost-legally" offered to the public as a substitute for the well-known, nationally advertised one. We then accompany Crofts' regular detective, Scotland Yard Chief Inspector French, through seven chapters of detection, alibi checking and interviews, following the book's only murder. We finally read four or five chapters devoted to the trial of two murder suspects.