The film tells the story of an ambitious young man, Tom, who loves Grete, daughter of the manager of the national railroads; but Grete's father prefers Lund, an upright and uptight army officer. To prove his worth, Tom organizes a daring robbery of the nightly Bergen Express in the hopes of outwitting his rival, who's been assigned to track down the thieves.

Suddenly appearing in Florence, an evil seductress causes Cesare, the city's ruler, and his son to both fall madly in love with her. The son, killing his father before an order to torture the woman can be carried out, then turns the city's churches into dens of sexual debauchery. Acts of evil and corruption continue unabated until the arrival of Death, who brings with her a horrible plague which she is about to loose upon the city.

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.

There are many ways to travel! Rich Director Brown's two young daughters prefer a first-class coupe in a high-speed train. While the train whizzes along the rails on its way to the big city, the young ladies in a strange way meet two strange guys, one long and thin, the other small and thick ... Fy and Bi! Fy and Bi are on their way to the capital to look for a place, they have an introductory letter with them, and it turns out that it is for the young ladies' father. The two young ladies promise to put a good word in for them, but director Brown receives Fy and Bi with much distrust, and he throws them out. Through many trials and a breathtaking ride in a motorboat, however, Fy and Bi manage to make a good impression on the director.