Still Dead

''Still Dead'' is widely considered by critics to be the best and most complex installment among Ronald Knox's detective fiction works. Featuring Miles Bredon, an investigator for the Indescribable Insurance Company, the story takes place in the Scottish Lowlands at Dorn, the estate of a Scottish Lord. Colin Reiver, the dissipated heir to the estate, is found dead by the roadside. Before help arrives, his body vanishes, only to reappear later at the exact same location.
The mystery is not how he died (it was natural causes), but when. Determining whether he died on a Monday or a Wednesday determines whether his massive life insurance payout goes to his family or to a religious sect his father joined.