Two nights later, Eugène sets out for the duchess' ball with his cousin Mme. de Beauséant. There he is greeted by Delphine and introduced to high society people, who invite him to their houses. He then realizes that he is being accepted in Parisian aristocracy and envied by many on account of his intimate acquaintance with Mme. de Beauséant.
The next morning, he tells the boarders at the pension of his triumphant evening. Vautrin, in a sarcastic and rather diabolical way, whispers that in order to keep up this kind of life Eugène will need money-money to move to a more fashionable neighborhood, money for new clothes, money for gambling — and how will you get this money, Vautrin adds, looking cunningly at Mlle. Taillefer?
The following weeks Eugène spends with Delphine, dining with her almost every night and taking her out afterward. He gets up at noon, walks in the Bois de Boulogne with Delphine whenever the weather is fair, and gambles heavily. From his first winnings, he repays his mother and sister and sends them presents.
But this situation cannot last, and after a while Eugène finds himself without money, not wanting to give up Delphine, and determined to maintain his social life by any means. His preoccupied attitude at the dinner table is quickly noticed by Vautrin, who pretends to leave the room but slyly stays on to spy on the young man. He overhears Eugène asking Victorine Taillefer whether she would love a poor young man if she were to become rich. Vautrin then reappears shouting, in a jocular tone, that the two young people have become engaged.
The ladies having left for bed, Vautrin and Rastignac stay together. Vautrin acknowledges that he has guessed that Eugène is in debt and offers to lend him three thousand francs. At first Eugène refuses with indignation to be obligated to Vautrin, but when the latter presents it as a business proposition at a high rate of interest, the young man accepts and Vautrin leaves him, implying that he will proceed to initiate his plan.
That evening, Eugène sets out to Mme. de Restaud's, pays his debts to M. de Trailles and M. d'Ajuda, plays whist, and wins back all he has lost.
The next morning, he promptly repays Vautrin, collects his promissory note, and repeats that he wants no part in the plot. Vautrin pretends not to listen to him.
Eugène continues his climb to the high circles of society. He has now given up studying, spends his time with Delphine, and gambles heavily. At first successful at the gaming table, he is able to keep pace with the financial demands of social life and even repay his mother and sister, buying them presents to appease his conscience. But very quickly the young man finds himself penniless and turns toward the potentially wealthy Victorine, becoming an easy prey for Vautrin, who finally succeeds in having him accept a note for three thousand francs and suggests that he is going ahead with his murder plot. Eugène is filled with horror and remorse. He gambles again, wins, and, with a sigh of relief, returns Vautrin's note.
This section depicts Rastignac's dramatic conflict between honesty and ambition, and Vautrin appears here as the devilish tempter, closely resembling the Mephistopheles in Goethe's Faust, then popular in France: "Ah! If only you'd let me teach you, I could make you achieve anything in the world. Everything you could possibly desire would be instantly granted, whatever it was: honor, fortune, women."
There is also in Rastignac's quest for money and love a strong resemblance to Balzac as a struggling young writer.