When Professor Marchand a famous scientist mysteriously disappears the commissioner Juve immediately suspects Fantomas. Meanwhile the journalist disguised as Fandor Lefevre Marchand's assistant is removed by Fantomas. Commissioner Juve falls into the trap as Fantomas too is transformed into Lefevre and they are all found in Rome at a scientific meeting. Fantomas will prevail and stakeholders will gather in his den and prisoners it seems without any possibility of escaping their fate. Accompanied by the music of an organ played by Fantomas.