The Jacob Street Mystery by R. Austin Freeman

"It would be a paradox," Thorndyke began, "to say that the unravelment of the complex scheme for the murder of Lotta Schiller began before the murder was committed; but it is a fact that, as each of the later developments came into view, it found me with a body of considered data to apply to the solution of the problem presented. At first, this was not an investigation ad hoc. Until Penfield proposed his case to me, I was an outsider, watching with little more than academic interest the unfolding of a train of events in which I was not personally concerned. Hence, when the question of the Presumption of Death was raised, I had not to embark on an investigation de novo, but only to test and verify conclusions already formed.

"For me, the starting-point was the murder of Charles Montagu. The interest of that crime from a medico-legal point of view lay in the unusual method adopted by the murderer -- the forcible administration of poison. But there were other elements of interest, and, thanks to Polton's enthusiasm, we were kept fully supplied with the published records of the case. We had the lurid descriptions of the murder and of the mysterious artist on whom suspicion at first lighted, and a full report of the inquest; but above all, we had Pedley's remarkable little picture of Gravel-pit Wood.