The late Richard Abernethie's solicitor, Mr. Entwhistle, turns to Hercule Poirot after Richard's sister Cora is killed with a hatchet the day after suggesting to other family members that her wealthy brother's death may not have been natural. The bodies seem to be piling up at Enderby Hall as her companion is sent a sliver of wedding cake steeped in arsenic. A mystery complete with genealogical tree, a dubious will, and a family full of potential murderers. Inspector Poirot investigates.