One, Two, Buckle My Shoe
Agatha Christie
 Hercule Poirot leaves the office of his dentist, Morley, after an appointment, and notices the arrival of Mabelle Sainsbury Seale. He returns to her the shiny buckle that has fallen from her shoe. Later, he hears from Inspector Japp that Morley has died of a gunshot. Between Poirot’s appointment and Morley’s death there were only three patients: Banker Alistair Blunt, Mabelle, and a Greek blackmailer named Amberiotis. The presence of a man thought essential to the country’s economic survival, the banker, Blunt, ensures Japp’s involvement in the case. Amberiotis dies of an overdose of anaesthetic and it is thought that the dentist has killed himself after realising the accident for which he had been responsible. The movements of people at the dental surgery are inconclusive. Morley’s partner, Reilly, is a rogue but seems to have no motive. Morley’s secretary had been called away by a fake telegram. Her boyfriend, Frank Carter, had a weak motive given that Morley had attempted to dissuade her from seeing him. Also present at the surgery was Howard Raikes, a prickly left-wing activist violently opposed to Blunt but enamoured of his niece. There is too little evidence for Poirot to construct an alternative hypothesis, but he senses that the story is not complete. When Mabelle goes missing, his fears are realised. A search for her is conducted, and some time later her body is apparently found in a sealed chest in the apartment of Mrs. Albert Chapman, who has herself disappeared. The corpse’s face has been smashed in, and Poirot notices its dull buckled shoes. He is skeptical of the theory that Mrs. Chapman has killed Mabelle and fled. Sure enough, once the dental records are produced by Morley’s successor at the surgery, it is discovered that the corpse is Mrs. Chapman’s. The hunt for Mabelle continues. Poirot is now drawn into the life of the Blunt family. An attempt is made on Alistair Blunt’s life at which Raikes is a bystander. Poirot is invited down to Blunt’s house, where he is persuaded to undertake a search for Mabelle. While he is there, a second attempt is made on Blunt’s life, but it is seemingly thwarted by Raikes. The pistol used in the attack is found in the hand of none other than Frank Carter, who has taken a job as gardener at the house under a false identity. When a maid at the surgery admits to having seen Carter on the stairs going up to Morley’s office, it seems that Carter is likely to be tried and convicted of both the murder and the attempted murder. The fact that the gun with which he was captured was the twin of the murder weapon only makes things worse for him. In the climax of the novel – one of the darkest in the Poirot series – Poirot realises that by allowing Carter to persist in his lies he can ensure that the real killer goes free, and wrestles with his conscience. Eventually he presses Carter to admit the truth: that when he entered Morley’s office the dentist was already dead. It is the final element in the puzzle. Poirot visits Alistair Blunt and explains the murders. The real Mabelle Sainsbury Seale had known him and his first wife, Gerda, whom he had never divorced, in India; his money came from his now deceased second wife, and he would be disgraced if caught in bigamy. Running into Blunt in the street, she had recognised and spoken to him in front of his niece, but had not realised whom he had become. By chance she had mentioned this chance encounter to the blackmailer, Amberiotis, who made the connection between the name 'Blunt' and the wealthy banker and began to blackmail Blunt. Gerda, posing under several aliases including that of Mrs. Albert Chapman, invited Mabelle to visit her, killed her, and took her identity, but had to buy new shoes because Mabelle’s did not fit her. This is why the corpse’s buckles were dull, while the buckle of the woman whom Poirot met going into Morley's surgery were shiny: the fake Mabelle had newer shoes than the real one, who was by that time decomposing in the chest. The woman in the trunk could hardly have worn through a new pair of shoes in a single day. Ironically, the face of the corpse had been disfigured not because it wasn’t Mabelle, but because it was. Alistair Blunt had attended his appointment, shot Morley and stashed his body in the side office with his wife’s help. Having appeared to leave the surgery, he returned and changed the dental records of Mrs. Albert Chapman and Mabelle in order to ensure that the corpse would be identified as Mrs. Chapman: a woman who in reality did not exist; the motive for killing Morley was simply to prevent him from detecting this change. At the end of Mabelle’s appointment, Gerda left, while Blunt dressed as a dentist in order to administer the overdose to Amberiotis, a new patient who had never met Morley. Poirot’s involvement had forced Blunt to compound the lies with talk of assassins and spies as the detective had relentlessly tracked the truth. At the novel’s bleak conclusion, Poirot is forced to admit that Blunt does indeed stand in public life “for all the things that to my mind are important. For sanity and balance and stability and honest dealing”. Nevertheless, he adds: “I am not concerned with the fate of nations, Monsieur. I am concerned with the lives of private individuals who have the right not to have their lives taken from them.” He turns Blunt over to the police. Later, he confronts Blunt's niece and her fiancé Howard Raikes, telling them that they now have the "new heaven and the new earth" that they desire, asking them only to "let there be freedom and let there be pity". In the last chapter, Mr. Barnes tells Poirot that he took such a vivid interest in the case as he was Mr. Albert Chapman, the wife of whom Gerda (apparently Mrs. Albert Chapman) pretended to be.