Over dinner at a London restaurant, Hercule Poirot listens to his friend Henry Bonnington hold forth on the comforting predictability of human routine. Bonnington points out an elderly, white-bearded regular who has eaten there on the same two evenings each week for years, ordering with the unvarying precision of a man wedded to his habits. Weeks later the two diners meet again, and Poirot learns that the old gentleman has died after a fall down the stairs of his lonely house, his body discovered only when the milk bottles piled up on the doorstep. To most observers it is an unremarkable accident, the quiet end of a poor and solitary painter. Poirot's curiosity settles instead on a single trivial detail he cannot let go: shortly before his death, the creature of habit broke his routine and ordered a meal entirely unlike anything he had ever chosen. That small deviation nags at the detective until he begins to pick at the threads of a tidy, well-arranged death. In the compact, unhurried manner of Christie's later short fiction, this is a puzzle built from the smallest things, an observation about what a man eats and how, rather than a chase or a confrontation. Poirot's method here is pure reasoning, the patient reading of ordinary behaviour for the one note that does not fit.