- Alliterative Title: "Monsieur Murdoch"
- The Beard: Roderick Dalewood is homosexual and his marriage to Sophie was one of mutual convenience arranged by letter. Learning about this during the ocean voyage from France to Canada is what inspired Jacqueline to murder the real Sophie and take her place.
- Dead Man's Chest: The Victim of the Week is found stuffed into a steamer trunk at Union Station.
- Europeans Are Kinky:
Guillaume: Monsieur Murdoch, the marriage is about family. You make babies with your wife. But you make love to your mistress.
- When Murdoch goes to talk to Guillaume at his hotel, a young lady emerges from the bedroom having apparently spent the night. Murdoch asks whether she's the detective's wife, and Guillaume says no; they just met last night in the hotel. Then another lady comes out of the room wearing a robe and nightgown, clearly having also spent the night. This, Guillaume explains, is the wife.
- Guillaume also encourages Murdoch to pursue a romance with Julia, claiming that the fact that Julia is engaged to another man only makes the situation more ideal.
- French Jerk: Averted by Inspector Guillaume. Despite a bit of early friction he's actually very pleasant and helpful, and he and Murdoch are able to collaborate very well on the case. He even offers Murdoch some questionable but well-intentioned romantic advice regarding his relationship with Julia.
- Historical Domain Character: Inspector Marcel Guillaume, the real-life Securite Paris detective who inspired Georges Simenon's Inspector Maigret, happens to be in Toronto for a conference on international police cooperation and is asked by Monique's father to investigate her disappearance.
- Kill and Replace: The killer's plot. She murdered and took the place of a woman sailing for Canada from Paris, who met and agreed to marry a wealthy man over the telegraph (her fiance therefore never saw her face). However the plan was threatened when her victim's sister came to visit. She kidnapped and imprisoned her, and hired another woman to masquerade as her for the husband's benefit. She then murders the sister and frames her husband for the killing to get access to his entire fortune when he hangs.