Mylène Demongeot later claimed that a fourth episode called "Fantomas à Moscou" ( "Fantomas in Moscow") was planned to follow, but apart from the fact that Jean Marais was tired of feeling second billed after the then conformed star Louis de Funès, the project failed to materialize because the trio of leading actors had grown far too expensive.
The trivia item below may give away important plot points.
One of Fantomas henchman(the one who is caught and tied up) already died in the 2nd part. He and another henchmen shot each other with cigar guns inspector Juve gave them. It seems that the team missed that fact or ignored it.