Harlander, a media mogul and war profiteer, has been told that he has six months before his sanity will leave him completely. He hires a young nurse, and decides to spend all his money before his six months are up.

Harry Yquem buys his beloved wife some jewelry in a place where underworld middlemen trade in fake and stolen goods. By chance, he spots a man with whom his wife had an affair in the past.

Dr. Mabuse and his organization of criminals are in the process of completing their latest scheme, a theft of information that will allow Mabuse to make huge profits on the stock exchange. Afterwards, Mabuse disguises himself and attends the Folies Bergères show, where Cara Carozza, the main attraction of the show, passes him information on Mabuse's next intended victim, the young millionaire Edgar Hull. Mabuse then uses psychic manipulation to lure Hull into a card game where he loses heavily. When Police Commissioner von Wenk begins an investigation of this mysterious crime spree, he has little to go on, and he needs to find someone who can help him.