Set in Paris, the film involves Ariane Chavasse (Hepburn), a young music student and the daughter of private detective Claude Chavasse (Chevalier), who is investigating the trysts of American businessman Frank Flannagan (Cooper). Upon learning that a jealous husband is about to shoot Flannagan, Ariane attempts to warn him personally, leading to a budding relationship between the two.
Mostly acknowledged to be Wilder working In the Style of... one of his filmmaking mentors, Ernst Lubitsch. This was also Wilder's first collaboration with screenwriter I. A. L. Diamond; the pair would work together on ten more films, including such classics as Some Like It Hot and The Apartment.
Tropes used in the film:
- At the Opera Tonight: Both Ariane and Frank attend the opera with different people. Ariane can only focus on Frank, and Frank can only focus on how bored he is.
- Bilingual Bonus: The Japanese newspaper article on Frank Flannagan does not mention him, but rather reads "The great newspaper king Kane dies". This is the same article used in the montage in Citizen Kane, with the name and picture of Frank Flannagan added in.
- Blatant Lies: Ariane's romantic history.
- The Casanova: Frank Flannagan.
- Chekhov's Gunman: The cuckolded husband who features in the opening scenes and winds up causing Frank and Ariane to meet then disappears from the movie, until towards the end, when he pops pu again and recommends Ariane's father Claude as a detective for Frank.
- Diegetic Switch: The waltz "Fascination" is used as a motif for Frank and Ariane, both playing over the soundtrack and sung/played In-Universe. In one scene the music seems to be playing over the soundtrack while Frank's in the sauna, only for the camera to turn and reveal that Frank's musicians have actually followed him into the shower, and are playing, while soaking wet.
- Dogged Nice Guy: Michel makes his feelings for Ariane no secret, but she just brushes him off.
- Dress Hits Floor: In this case it's Fur Coat Hits Floor. Frank tells Ariane to take off her coat as the two make out, and we see the coat fall like a dress.
- Fake-Out Make-Out: Flannagan and Ariane pretend to make out when a jealous husband breaks into Flannagan's hotel room.
- Femme Fatale: Ariane pretends to be one to get Frank's attention.
- Gay Paree: Everyone is in love in Paris; children, animals, even the undertaker at a funeral!
- I'm Not Pretty: Ariane's opinion on her appearance: "I'm too thin, and my ears stick out, and my teeth are crooked and my neck is much too long."
- Ladykiller in Love: Frank with Ariane.
- MayDecember Romance: Ariane is stated to be 18, and though Frank's age isn't given, no attempt is given to make his character seem young. Cooper was 55 at the time of filming and Hepburn was 28 in Real Life. The large age gap was one reason for the poor critical reception the movie received.
- Missing Mom: Ariane's mother.
- Overprotective Dad: Mr. Chavasse doesn't let Ariane read his case files and has a full dossier on Michel, though he is quite level headed when comes to confronting Flannagan.
- Police Are Useless: They can't investigate until after a crime has been committed.
- Pretty in Mink: Ariane borrows an ermine coat as part of her first seduction of Frank. The coat was a gift a rich man planned to give his mistress, then his wife after the reconciled, and then his mistress again when he saw his wife wearing an apparent trinket from an affair.
- One of Frank's dates wears a white ermine wrap when they attend the opera.
- Really Gets Around: Frank Flannagan.
- Running Gag: With the lady and her dog in the neighboring hotel room.
- Sherlock Scan: While Mr. Cravasse takes a while to catch onto his daughter having an affair with Flanagan, he shows eerie observational skills in some situations. For example, he knows that Ariana hasn't been with Michel because she has a callus from carrying her own cello case.
- They Do: Frank and Ariane are Happily Married at the end, as Ariane's father narrates.
- Translation Convention: The French characters speak English among each other.
- Twin Threesome Fantasy: Frank Flannagan mentions meeting a pair of twins in Sweden. Later, they call him up when they get to Paris.
- Worst News Judgment Ever: If the clippings that Ariane seeks out are any indication, the entire world has nothing to talk about other than Frank's love life.