Judge Dempsey and opera singer "Gus" Di Ruvo, whose stage name is Tino Caraffa, are longtime residents of an apartment complex located over a speakeasy owned by Tomasso Antiovi. One night, East Coast snob Henry Greene brings his innocent southern fiancée, Isabelle Parry, in to the speakeasy for a drink, and the judge befriends her. Henry rebuffs him, however. When Gus, a notorious playboy, comes in, he is immediately drawn to Isabelle, who is thrilled when she learns that he is the famous Tino Caraffa. Policeman Mulligan comes in and asks Henry to move his car, which he has parked in a manner that endangers public safety. Henry immediately wants to leave, but Isabelle wants to stay, so Henry and Tomasso go outside to look at the car. Henry is convinced that Mulligan put his car in front of the fire hydrant himself and, when he returns to the bar, becomes incensed to learn that Isabelle has been dancing with Gus. Henry's language becomes insulting, and when he demands that Isabelle leave with him, she refuses and returns his engagement ring, after which he calls her "lazy white trash." Henry returns with Mulligan, whom he has told that Isabelle is being kidnapped. Over a drink, however, the judge informs Mulligan that Henry had earlier accused him of bribery, and Mulligan, outraged by the insult, arrests Henry for public disturbance. In the meantime, Isabelle and Gus have become friends, and he offers to put her up for the night, as she has nowhere to go and he is crazy about her. When she asks him about his intentions, he affirms that they are "strictly dishonorable." Later in the evening, the judge intrudes on Gus's apartment in an attempt to protect Isabelle from Gus. Gus goes downstairs when a lover, Lilli, arrives for an impromptu visit, and while he is away, the judge tells Isabelle she must return home the next day. She reveals that, although she never loved Henry, she does love Gus and cannot return home unmarried, as her family would think something was wrong with her. The judge warns her that Gus will never marry her, but Isabelle is adamant about staying. After Gus returns and the judge leaves, Isabelle notices that Gus's apartment is set up for a woman to spend the night, but stays nonetheless. Gus is so overwhelmed by her sweetness and innocence, however, that he spends the night in the judge's apartment. In the morning, Gus confesses to the judge that he is in love with Isabelle and has cabled his mother in Italy to ask her permission to marry, but makes the judge promise that he will not tell Isabelle yet. In the meantime, Henry arrives, fresh out of jail, and asks Isabelle to return to him. Although she can offer him no proof, she assures him that she is still a "virtuous maid," while maintaining that her virtue is no one's business but her own. She then asks Henry if he is still "pure," but he is astonished by her forward manner and tells her it is "entirely different" for him. Isabelle reluctantly agrees to remain engaged to Henry, who goes outside to wait for her after thanking Gus for his hospitality. When they are alone, Gus proposes to Isabelle, but she does not believe his expression of love and leaves. The judge delivers to Gus a cable from his mother approving the marriage, and Gus dejectedly joins the judge for a drink in his room. When they go in, they find Isabelle there, crying. After she tells Gus that she does indeed love him, the judge goes to tell Henry not to wait.