Quand le professeur Marchand, un célèbre scientifique, disparaît mystérieusement, le commissaire Juve soupçonne tout de suite Fantomas. Entre temps le journaliste Fandor se déguise en Léfèvre, assistant de Marchand, et il est enlevé par Fantomas. Mais également le commissaire Juve tombe dans le piège pendant que Fantomas, lui aussi, se déguise en Léfevre et ils se retrouvent tous à Rome à un congrès scientifique. Fantomas aura le dessus et les intéressés se retrouveront dans son antre, prisonniers et, semble-t-il, sans aucune possibilité d'échapper à leur destin, accompagnés par la musique d'un orgue joué par Fantomas.
In the second installment of the parodic Fantomas series, the title arch criminal and master of disguise kidnaps prominent scientist Prof. Marchand in order to develop a new powerful weapon to threaten the world. Fantomas is also planning to kidnap another scientist, Prof. Lefebvre. Journalist Fandor (Jean Marais, who also plays Fantomas and Prof. Lefebvre) decides to set a trap for the elusive villain. He disguises himself as Lefebvre and attends a scientific conference in Rome expecting Fantomas to kidnap him. As always, Fandor's ingenious plan backfires due to the interference of the bumbling police commissioner Juve (Louis de Funès).
A child's resilience and the kindness of strangers. Thuy is 10, an orphan, working in her uncle's factory outside Saigon. He berates her constantly, so she runs away to Saigon. Over five days, we watch her survive on the streets selling flowers, while her uncle looks for her. She encounters Hai, a reserved zoo-keeper whose fiancée has jilted him. She also sells a flower to Lan, a flight attendant in the city for a layover, unlucky in love, who buys dinner for Thuy and offers her a place to stay that night. Thuy, who thinks of Lan as a sparrow and Hai as an owl, determines to bring them together. If she succeeds, then what; and what about her uncle?