Several evenings after the Bellegardes' ball, Newman goes to Don Giovanni alone, intent on enjoying the opera without the constant chattering of companions. As he waits for the music to begin, he notices Urbain and the young Marquise in one of the plush boxes, and Noémie Nioche with a young man in a smaller box.
En route to the Bellegarde box for a courtesy visit, Newman encounters a distraught Valentin. Valentin reveals that he cannot stop seeing Noémie, though it is clear to him that she is scheming and often cruel. Newman earnestly repeats his earlier idea that Valentin return with him to America, where Newman can get his friend a job in a bank.
At the Bellegardes' box, Newman naïvely discusses Don Giovanni with Urbain and the young Marquise, revealing his ignorance on the subject. When Urbain retreats temporarily to the foyer, the Marquise confesses herself to be a modern woman trapped in a stifling and antique tradition. She asks Newman to take her secretly to the Bal Bullier, a famously rowdy student dance in the Latin Quarter—an event far beneath the Bellegardes' usual social orbits. As the curtain rises and Newman returns to his seat, he notices Valentin sitting in the same box as Noémie and her companion.
During the next act, Newman encounters Valentin in the lobby, now quite taken with the idea of American banking. The two friends discuss the possibilities at great length:
Newman's imagination began to glow with the idea of converting this irresistible idler into a first-class man of business. He felt for the moment a spiritual zeal, that of the propagandist. Its ardour was in part the result of that general discomfort which the sight of all uninvested capital produced in him; so charming an intelligence ought to be dedicated to fine uses.
Newman tries to dissuade Valentin from returning to Noémie's box, but for Valentin—who has been jilted by Noémie's companion—returning is a point of honor. At the end of the act, Newman observes Valentin and Noémie's companion excitedly leaving her box. Newman goes to see Noémie and finds her alone, looking elegant and perversely pleased at the prospect of a fight.