Maigret returns to his native village after receiving an anonymous letter warning that a murder will occur during the church service. Soon after, the Countess of the Saint-Fiacre estate dies. What first appears to be a natural death is revealed to be a murder.
During his investigation, Maigret uncovers financial troubles, inheritance disputes, and deep family conflicts within the declining aristocratic household. He eventually identifies the culprit and solves the case.
The investigation also brings Maigret face to face with memories of his childhood and the disappearance of the world he once knew.