"Hercule Poirot's Christmas", the Agatha Christie story on which this episode is based, was also previously the inspiration for the miniseries "Petits Meurtres En Famille", which first introduced the characters of Larosière and Lampion and was essentially the pilot for this series.
The writers once again recycle a plot line already used during the Larosière/Lampion era of the show. In "Le Chat Et Les Souris" Larosière runs into an old flame and discovers he has a daughter he never knew about; in this episode Laurence runs into an old flame and discovers he has a son he never knew about. In both episodes the old flame becomes a murder suspect, as well.
The role of Thierry is played by Alexandre Labarthe, Samuel Labarthe's real-life son.