On the street in Venice, Gratiano, Lorenzo, Salerio and Solanio discuss Lorenzo's plan to elope with Jessica that night, before the dinner at Bassanio's. They are interrupted when Launcelot enters, carrying Jessica's letter.
Unlike Portia, and her suitors who follow her father's legal dictates, by eloping Lorenzo and Jessica circumvent typical legal structures to get married.
Reading the letter, Lorenzo is overjoyed and remarks that Jessica's "fair hand" is "whiter than the paper it writ on" (2.4.12). When Launcelot reports that he is headed back to his former master, Shylock's, house, to invite Shylock to dinner on behalf of his new master, Bassanio, Lorenzo asks Launcelot to secretly bring Jessica the message that Lorenzo will not fail her. Launcelot agrees.
Jews were typically depicted as darker than Europeans. Notice how Lorenzo describes Jessica, who will betray her father and fellow Jews, as white. He seems to believe that Jewishness is more an aspect of personality than biology.
Once Launcelot has left, Lorenzo and the others make plans to put on a fake "masque" (costumed show) as a cover to hide the elopement. Salerio and Solanio exit, leaving Lorenzo and Gratiano alone. Lorenzo then tells Gratiano that Jessica's letter contained instructions on how to help her escape from her father's house, where she has stolen gold and jewels from Shylock to take with them. Jessica, Lorenzo concludes, will flee with them tonight, costumed as his torchbearer.
It turns out that Jessica will not only abandon her father and avoid the traditional legal framework for getting married, she is also going to rob her father to provide herself and her husband with money. As in Bassanio's suit of Portia, romantic conquest and commercial gain are mingled. They all seem to think that stealing from a Jew is no big deal.