Werner Dux, heir of the big car company "Dux-Werke", is a gambler who has just been arrested in Chicago for shooting a cardsharper. While in jail, he learns from his friend Michael Nissen that his father has died recently. That means that the Dux-Werke are without a leader at the moment, for Werner's cousin Steffie, who is his co-heiress, is still too young to run the firm. In this situation, Werner convinces his friend Michael, who is an engineer by profession, to take over the firm as long as he is in jail and to pose as him. Michael agrees and is able to bring the firm up again. He even arranges a reliability test for motorcycles via Istanbul, Rome and Barcelona, which creates a big Turkish order for the company. When the real Werner escapes from jail and arrives in Germany, it looks as if the whole story is up to bust. But Werner needs money, so he convinces Michael to go on as before and hand over all profits of the firm to him.