Everyone in Paris thinks Fantomas is dead. A wave of extortion, blackmail and murder all point to the master criminal. Inspector Juve and his reporter friend Fandor set out to find the truth. They discover the crimes are being committed by a gang aided by human automatons created by advanced brain surgery. They track the gang to a castle in a forest. There, they confront a mad scientist masquerading as Fantomas. Before they can capture him, the real Fantomas intervenes. He has been involved all along and has big plans for the scientist.