In Fritz Lang’s last film as a director, Dr. Mabuse, the super villain of the Weimar Republic, returns, although he had been admitted to a mental asylum at the end of "Dr. Mabuse, der Spieler" ("Dr. Mabuse: The Gambler") and had died at the end of "Das Testament des Dr. Mabuse" ("The Testament of Dr. Mabuse"). His successor wants to put Mabuse’s plans into action. He controls a luxury hotel that is equipped with surveillance cameras after Gestapo plans. The American multi-millionaire Travers falls in love with Marion, a girl that Travers saved from dying twice, as he is made to believe. But actually, Mabuse had hypnotized Marion to get to Travers. He wants to take control of his nuclear plants to cause a world-wide chaos. Fortunately, Travers and Marion are saved and the criminal’s plans are thwarted. But is Mabuse really dead this time?