The journalist Fandor befriends the King of Hesse-Weimar during one of his Majesty's incognito pleasure trips to Paris, but when the King's mistress is found dead, having fallen from a third-floor window, Inspector Juve is called upon to investigate. When the indomitable detective discovers Lady Beltham, the lover of Fantômas, in disguise among the royal court of Hesse-Weimar, Juve suspects it is none other than the Lord of Terror who is behind the plot against the King.

"From the imaginative standpoint Fantômas is one of the richest works that exist."
-Guillaume Apollinaire

"Absurd and magnificent lyricism."
-Jean Cocteau