First published 1937 by Collins Ltd (UK). US title: 'Poirot Loses a Client.'
Miss Emily Arundell is an elderly spinster who has a lot of money and three nieces and nephews who would do anything to get their lazy, greedy hands on it. When Miss Arundell takes a fall down the stairs late one night, with all of her family present in the house at the time, she realizes this wasn't really an accident caused by her dog, Bob: this was an attempt on her life.
Miss Arundell does two things. First she writes a letter to Hercule Poirot, asking for his help. Then she writes a letter to her solicitor, requesting that her will be changed to show only one beneficiary - her companion, Miss Lawson. The will is duly changed, but Poirot doesn't receive his letter until two months later, and by then it is too late: Miss Arundell is dead, supposedly by natural causes.
As always, Poirot relishes a challenge, and even though his client is dead, he begins investigating and realizes that Miss Arundell's death was far from natural. He meets the nieces and nephews who were shellshocked when the will was read out: Charles, the immoral playboy who would do anything for money; Theresa, the beautiful socialite who has almost run out of cash to fund her lavish lifestyle; and Bella, a scatterbrained, unfashionable woman who lives for her children. Bella's husband, Theresa's fiancé and Miss Lawson are also quickly added to Poirot's list of suspects.
Poirot is assisted by his good friend Captain Hastings, who also narrates the story. As usual, Hastings is no further to working out who the killer is until Poirot stages his dramatic denouement at the end of the book.
This is not one of Christie's best, but it is still enjoyable. Unfortunately it includes one of my pet hates about Christie mysteries (she seems to have employed this plot twist more than other writers did at the time) - she allows the killer to commit suicide, which always frustrates me.