介绍：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.