After his failed attempts to capture the ruthless crook and serial murderer Fantômas, Inspecteur Juve becomes the victim of a virulent press campaign which accuses him of being Fantômas himself. Whilst Juve languishes in a prison cell, his friend, journalist Fandor, attempts to clear his name by tracking the real Fantômas. Meanwhile, the police are investigating the disappearance of a debt collector. An American detective Tom Bob finds the body concealed in a newly built wall and offers to carry out his own investigation to find Fantômas. Lady Beltham, former lover and victim of Fantômas, receives a visit from Tom Bob, whom she instantly recognizes as Fantômas. The arch-criminal compels her to organize a charity ball, ostensibly to raise funds to bring Fantômas to justice. Hearing about the ball, and suspecting that Fantômas will almost certainly be there, Fandor decides to attend, dressed as the infamous criminal.