After a suspicious fall on the stairs, wealthy Emily Arundell writes to Poirot but dies before he receives the delayed letter. Her relatives expect to inherit, yet a late change to her will and the testimony of her wire-haired terrier Bob complicate the apparent natural death.
Poirot and Hastings enter the household under a pretext and examine spiritualist performances, financial need and the family’s assumption that an elderly woman’s property should already belong to them. The case contrasts affectionate appearances with entitlement and shows how a small domestic detail can preserve evidence after human witnesses have altered their stories.