Patrick 是一个年轻人,他父亲在远方经营着一个浴场,而他在一次交通事故中受伤陷入了昏迷状态。几年后,几个不同的人来到了他所在的医院:一个有野心的政治家和他的妻子,一个有投资商的儿子是个游泳明星,说话刻薄的男人,还有一个女人;这五个人同时到达住在不同房间,迎接他们的是医生的新助手 Lydia 和两只恶犬,狗的主人警告那个游泳明星 Davis 让他离开 在医院的一间封闭的病房里,躺在床上的 Patrick 被和三个昏迷的人帮在一起。医生究竟有什么邪恶的目的呢?客人们一个接一个的因为没有接受警告,而惹上了麻烦。那么 Patrick 是否是有知觉的呢?
Poirot pays what appears to be a routine visit to Dr. Morley, his dentist, but shortly after he leaves the clinic, the doctor is found dead with a gunshot wound to his temple, an apparent suicide. Poirot suspects foul play, and all those who entered the doctor's offices after Poirot left are suspect. They include Alaistair Blunt, a prominent and very influential bank director, Frank Carter, a young fascist thug with a personal grudge against Morley, Mr. Amberiotis, an enigmatic recent arrival from India suffering from a toothache, and Mabelle Sainsbury-Seale, a charity worker also recently returned from India. When Amberiotis is found dead in his hotel room from an overdose of Novocaine and Sainsbury-Seale disappears, Poirot rightly expands his list of suspects and connects the crime to events that occurred in India 12 years earlier.
When Tommy and Tuppence visit an elderly aunt in her nursing home, Tuppence is concerned by the odd behavior of some staff and residents. So when Tuppence hears about Aunt Ada's sudden death and the disappearance of her friend Mrs Lancaster, she realizes her concerns were right. Tuppence meets Miss Marple and together they follow a path of clues that lead them to the Norfolk village of Farrell St Edmund, where they find a community guarding an array of secrets. Only by getting to the bottom of these secrets do they begin to unravel the truth about the mystery of Aunt Ada's death and Mrs Lancaster's disappearance.