One afternoon at Mrs. Lucretia Green's high class boardinghouse, Alvin Hillyard, a struggling young composer, witnesses a drunken man abusing a young woman in the tenement yard next door. He climbs out the window and saves the girl, Louise Howard, then carries her to the boardinghouse, where Mrs. Green comforts her. Mrs. Green offers Louise a room in exchange for helping around the house, hoping to keep her safe from her violent, drunkard stepfather, Spike. Meanwhile, Eddie Blake, a saloon owner and another one of Mrs. Green's boarders, encourages Spike to drink and then tries to drag Louise back to her father as he wants to hire the girl, to whom he is attracted, as an entertainer in his seedy club. Alvin once again intervenes, and Mrs. Green tells Eddie to pack his bags while Alvin vows to teach the lout how to have respect for "our" women. Later, at a saloon, Spike and Eddie discuss Louise, and Spike tells the ruffian to leave the girl alone, blaming his own violence on the alcohol that Eddie has given him. Eddie proceeds to push alcohol on the susceptible Spike, and after he has become thoroughly inebriated, he goes to Louise's room and tries to grab her. Alvin rescues Louise once again and then decides that he will marry her so that she will finally be safe. Three months later, Spike, in a state of alcohol withdrawal, begs Eddie for a drink, and Eddie says he will serve him only if he helps kidnap Louise and set up a cabaret in another town, where with her looks and his brains they will make a killing. The pair devises a scheme which involves sending a fake telegram calling Alvin away to his sick mother's bedside. As Alvin packs to leave, Louise offers to accompany him, but Alvin confesses that he has never told his class-conscious mother about their marriage. Alvin leaves as Spike watches the house, and Louise, distraught, ruins a photo of Alvin's mother and then discovers and tears up letters in which the matron mentions her hopes that Alvin will marry a young woman of their own class. Her final acts of defiance are to remove her wedding ring and tear up her marriage license. Although Spike has tried to dissuade him, Eddie enters Louise's room and then tells her to join him in a business deal in another town, a proposition to which Louise agrees, provided their relationship remains strictly business. Alvin discovers the trick played upon him once he arrives at his mother's home and, having dropped his house key, breaks into his and Louise's room through a window and pulls a gun on the pair. The two men fire their guns, and when the police arrive, they find Louise unconscious and wounded. Alvin is convicted of assault based on Louise's testimony, and the girl is left with a disfiguring scar on her neck. Later, Alvin escapes from prison and becomes a successful music teacher under the name "Arthur Jones" in the same city where Louise and Eddie have set up a chic gambling club, the Club Lido. Alvin begins to fall in love with his star music pupil, Alice Hathaway, but cannot declare his feelings because of his past. One day, her father, Ralph Hathaway, a wealthy lawyer, receives a call from Louise inviting him to come to a "whoopie" party at the club, of which Hathaway is the sponsor and protector. When a letter is left for Hathaway, Alice, now engaged to Alvin, asks her fiancé to bring it down to the club, where much to his shock, he is introduced to Louise. Louise blackmails Alvin into dancing with her in front of Hathaway, and then later into coming to visit her at her home. When he arrives, she tries to seduce him, then confesses that she has always loved him. He throws her down and leaves, and, distraught and hopeless, Louise writes a letter and asks her maid to deliver it to Hathaway. She begs God's forgiveness and drinks poison, and when her maid tries to revive her, she begs her to simply deliver the letter. The maid calls Hathaway to come to Louise's side, and before he arrives, Eddie enters the room and finds a letter informing him that she finally plans to clear Alvin's good name. Hathaway arrives, reads his letter, and exclaims in sorrow that his people have much to learn. In the meantime, Alvin, having confessed all to Alice, tries to comfort her, but Hathaway arrives bearing the truth conveyed in Louise's letter: that Eddie had actually shot Louise, who is now dead, and that Alvin is innocent. Alice and her future husband, now exonerated, embrace.