Former postal clerk Nikodem Dyzma arrives in Warsaw looking for work. By chance, he comes across an invitation to a banquet. He decides to attend, hoping for a good meal. At the event, he gets into a quarrel with a man named Terkowski. Surprisingly, instead of being thrown out, he receives praise and becomes the star of the evening. Influential guests welcome him into their circle. He meets Colonel Wareda, Minister Jaszuński, and landowner Kunicki, who offers him a job managing his estate in Koborowo. Dyzma leaves his rented room on Krochmalna Street, says goodbye to a prostitute named Mańka, and sets off to begin a new life.

An advance payment from Kunicki allows Dyzma to dress properly. When he arrives in Koborowo, he impresses the ladies—Kunicki’s wife Nina and his daughter Kasia. However, when he meets Nina’s brother, the eccentric Żorż Ponimirski, Żorż sees through him. They strike a deal: Dyzma promises to help the legally incapacitated Żorż in exchange for education. Żorż also tells Dyzma about Kunicki—who he is and how he came to possess the Ponimirski estate.

Dyzma travels to Warsaw with the task of securing a timber allocation from Minister of Agriculture Jaszuński for Kunicki’s sawmills. He contacts Colonel Wareda, who helps him gain access to high society circles in the capital. Dyzma presents Kunicki’s idea for saving agriculture to the Deputy Minister as his own, earning a reputation as a “brilliant mind.” He also meets Countess Przełęska, Nina and Żorż’s aunt, who introduces him to aristocratic salons. Together with her lover, Zyzio Krzepicki, they begin plotting how to free Nina from the conman Kunicki.

Dyzma returns to Koborowo as a hero. He has solved the timber allocation issue and no longer fears losing his job. Kunicki’s wife begins showing him affection, which sparks jealousy in her daughter Kasia. Unexpectedly, Dyzma receives a summons to Warsaw. Impressed by his “brilliant” agricultural reform plan, the Prime Minister offers him the position of President of the Grain Bank. Despite some doubts, Dyzma accepts the offer.

Nikodem Dyzma takes over as President of the Grain Bank. His right-hand man becomes Zyzio Krzepicki, a cunning opportunist. With Zyzio’s help, Dyzma rules the bank with an iron fist while indulging in high society. He meets Countess Koniecpolska, who invites him to her estate for a secret “lodge meeting.” As the “Grand Thirteenth,” he’s the only man among a dozen scantily clad society women. Back in Warsaw, danger looms: his former postal boss Boczek shows up, demanding a lucrative job and threatening to expose Dyzma’s past. To scare him off, Dyzma hires thugs.

Dyzma plots to get rid of Kunicki, seize the Koborowo estate, and marry Nina. Together with Zyzio Krzepicki, he orchestrates a scheme that leads to Kunicki’s arrest. A police commissioner, seeking Dyzma’s favor, offers Kunicki a deal: he’ll receive a passport and be allowed to leave the country if he renounces his claim to his wife’s property. Triumphant, Dyzma arrives in Koborowo as the victor, exclaiming: “Nina… the estate… the factories… millions… all mine…”.

After Kunicki’s marriage is annulled, Dyzma prepares to marry Nina. But trouble resurfaces: Terkowski, whose quarrel with Dyzma sparked his meteoric rise, now seeks to expose him. With help from the “Lodge of Twelve” ladies, the threat is neutralized. Dyzma resigns as President of the Grain Bank, seemingly in protest against government decisions, and returns to Koborowo. During a lavish estate reception, a presidential envoy arrives, asking Mr. Nikodem to accept the mission of forming a new government. Everyone is thrilled, and Dyzma considers the offer. Only the eccentric Żorż Ponimirski shouts, “Dyzma is a scoundrel and a fraud!”.