The Murder on the Links (Hercule Poirot, #02)

When Hercule Poirot and his associate Arthur Hastings arrive in the French village of Merlinville-sur-Mer to meet their client Paul Renauld, they learn from the police that he has been found that morning stabbed in the back with a letter opener and left in a newly-dug grave adjacent to a local golf course.
Among the plausible suspects are Renauld's wife Eloise, his son Jack, Renauld's immediate neighbor Madame Daubreuil, the mysterious "Cinderella" of Hasting's recent acquaintance, and some unknown visitor of the previous day--all of whom Poirot has reason to suspect. Poirot's powers of investigation ultimately triumph over the wiles of an assailant whose misdirection and motives are nearly--but not quite--impossible to spot.