Thomas Mann traces the progress of the "confidence man: of the title from his childhood through young adulthood. Felix, born and raised in Germany, begins life in a well-off family. Even as a child, Felix is captivated by acting after attending his first theatrical performance. His father, who makes champagne, unfortunately suffers serious setbacks, ultimately goes bankrupt, and, in despair, kills himself. These disasters prompt his family’s move from the countryside to Frankfurt. Felix is supposed to enter the military, but he fakes his way out of it. Thus released from doing his proper duty, he takes the train to France. En route, he steals a jewel case from another traveler.

Once in Paris, he starts work in a hotel, where he takes a different name and sells some of the jewels. In a convenient plot twist, he also becomes the lover of the wealthy woman who previously owned the jewels and, when it is revealed that he stole them, does not seem to mind. Felix uses his own name in his evening forays into Paris nightlife. He befriends a young nobleman who wants to stay in Paris with his charming mistress, but his parents want to send him away. Felix strikes a deal to impersonate the marquis and travel in his stead. On a train to Portugal, he meets a natural scientist, who provides the supposed aristocrat with an introduction to his family in Lisbon. While his daughter is initially captivated with Felix, it turns out that it is her mother whom Felix finally seduces.