Based on the novel "Lord Edgeware Dies" by Agatha Christie.
The character of Larosière's daughter Juliette, played here by Alice Isaaz, first appeared in the earlier episode "Le Chat Et Les Souris", played by a different actress.
In both this episode and the previous episode "Un Meurtre En Sommeil" a character is killed by being stabbed with a pitchfork.
This episode is unusual in that when a murder is committed at the very beginning, the killer's identity is revealed to the viewer, though Larosière and Lampion don't discover it until much later on in the story.