This talkative and unevenly paced feature finds Fou (Jean Lefebvre) the inventor of a gas that makes the users fall in love. He is chased by his boss, the police, and spies, who seek to secure the secret recipe for their own selfish purposes. A shadowy American underworld figure tries to intimidate the inventor. A half-hearted attempt at comedy tries to go along with the double dealing and trickery of the thin plot of the film.
 Jean Lefebvre
Eugène Ballanchon, scientific researcher, single
 Maria Latour
Régine, Mr. Beauchard's spy
 Bernard Blier
Mr. Beauchard, executive secretary linked to a gang
 Michel Serrault
Mr. Granger, director of the scientific laboratory
 Pierre Tornade
DST inspector
 Pierre Brasseur
Father Ballanchon
 Margo Lion
Mrs. Ballanchon, Eugène's mother
 Robert Dalban
Merchant, spy in the laboratory