Having committed murder in Belgium, Fantomas is sentenced to life imprisonment. Two crimes committed in France suggest to inspector Juve that the Fantomas gang is still at work. He conceives the idea that if Fantomas is set free it will be possible to follow him and capture him and the remaining members of the gang. The villain escapes from prison and makes his way to the railroad station and boards a train where he is tracked by private detectives. When the train stops at a country station, Fantomas alights with the intention of making good his escape, but he finds that he is being followed by two detectives, whom he recognizes. He goes back to his carriage, which leads the detectives to think he is quite safe, but he crosses the train and leaves by the opposite door, jumping into the baggage wagon of the train on the opposite rail. Just at that moment the train moves and a magistrate who happens to have nearly missed the train also jumps into the baggage wagon. Fantomas was who hiding, attacks the magistrate, and after a severe struggle in which he is victorious assumes the disguise of the magistrate and takes his clothes and papers. He continues the journey as the magistrate, successfully rescues certain criminals, who are brought before him to be tried, and manages to blackmail several members of society, with whom he is brought in contact. While here he is recognized by Fandor, the young and clever journalist who happens to come into the district and who has suspicions as to the authenticity of the magistrate. He decides to keep watch upon him. His suspicions are well founded and he identifies the magistrate as none other than Fantomas. After much trouble, he is able to get papers committing Fantomas to prison, but Fantomas' suspecting his immediate arrest, issues an order to the head warden, and tells him that it is Detective Juve's intention to be arrested disguised as Fantomas. The warden is not to tell a soul of the detective's intentional disguise, but is to let him remain in prison until 12 o'clock midnight, when the head warden is to personally release him. The police, not suspecting anything of this, feel quite safe when Fantomas is put in the cell and securely barred and locked. His scheme works favorably and once more Fantomas is at large.