On an ocean voyage, a librarian falls for a married man. After librarian Lulu Smith is accused by her patrons of having Spring fever, she spends her life savings on a cruise to Havana, during which she begins a romance with Bob Grover, a lawyer with political ambitions. After their return, Lulu becomes a clerical assistant for a newspaper, where she is pursued by brash reporter Al Holland. One night, several months into their affair, Bob comes to Lulu's apartment for dinner, bringing two Halloween masks with which they have a marvelous time playing. Their merriment is interrupted by a call from Al, whose proposal to Lulu prompts Bob to confess that he has an invalid wife whom he cannot leave. Lulu protests that she wishes to continue their affair, but Bob refuses to let her waste her life on him. They squabble, and Lulu throws him out without telling him she is pregnant. Time passes and Bob becomes district attorney, while Al becomes city editor of the newspaper. After Bob hires a detective, Marty, to find Lulu, the couple are reunited and Lulu introduces Bob to his daughter Roberta. Later, Lulu and Roberta are waiting to meet Bob, when Al suddenly appears. He is questioning her about Roberta when Bob arrives, and, in order to protect Bob's reputation, Lulu tells Al that the baby is Bob's adopted daughter and that she is her governess. In order to preserve the charade, Bob does adopt Roberta, taking her home the next day to present to his wife Helen, who is returning from a European rest cure. Helen is delighted with the child but questions Lulu's ability to care for her. Lulu runs out of the house, and when Bob follows her, she tries to tell him she is through with him but cannot. Soon after, Lulu goes to Al for a job and becomes the "advice to the lovelorn" columnist for his paper. Al pumps her for information about Bob and Roberta in order to write a story causing Bob's downfall, but Lulu refuses to say anything. As the years pass, Lulu still works for the paper, and Al, now the managing editor, is still pursuing her. Bob has been both a mayor and a congressman, but on the night he wins the nomination for governor, he becomes disheartened, ashamed of the hypocrisy of his double life. Lulu tries to talk him out of confessing the truth and ruining his career, but when it seems that she cannot succeed, she asks Al to marry her, hoping that will make Bob forget about her. On the night of Bob's election, however, Al tells her that he knows all about her, Bob and Roberta, and Lulu kills him to prevent him from publishing the story. A year later, Bob is on his deathbed, and Lulu, whom he had pardoned after a short jail term, comes to visit him. He shows her his new will, which tells the truth and leaves her half of his estate, but after he dies, she tears it up to protect him and Roberta, who is engaged to a socially prominent young man....