When a watchman at National Chemical Laboratories, Inc. finds the body of Myrtle Stanfield, he calls the police, who find two mysterious notes near the body that implicate the watchman. Three years earlier, door-to-door salesman Henry Glory sells a novel to a young woman named Claudia Vance, who lives with her mother. When Henry delivers the book a few days later, he is told by Claudia's neighbor that Claudia is a woman of ill-repute and is known as "Catbird." Soon after meeting Henry, Claudia coaxes Henry into admitting that he wrote the novel himself, anonymously, and that he will be using the profits from the sales to put himself through law school. Henry is immediately smitten with Claudia and the next day, tells Claudia's neighbor that he intends to tell Claudia at 8:30 that evening that he loves her. Meanwhile, two white men are seen plotting something that will take place at 8:30 p.m. That night, Henry arrives at Claudia's but is knocked out by a man who comes up behind him and mistakes him for the intended victim. Now, three years later, in 1934, after Henry reads the headlines announcing Myrtle's murder, Claudia shows up at his office and tells him that the accused watchman is her brother Harper, and asks him to take his case. Henry accepts the case, and after interviewing Harper, realizes that he was not at the factory at the time the murder took place. At the trial, Brisbane, the plant boss, takes the witness stand and states that, at noon, Myrtle and Harper entered a back room at the plant. Harper, however, denies that he ever saw Myrtle. Next, Myrtle's mother Stella testifies that Myrtle's boyfriend, George Epps, went to the chemical plant to get his paycheck and that she never saw her daughter again after that. Later, Henry and Claudia deduce that Brisbane, who has a perfect alibi, committed the murder and that he is trying to blame it on her brother. The following night, Catbird, who is actually Claudia's criminal neighbor, greets Lem Hawkins at a nightclub, and Claudia, who is also there, gets Hawkins drunk. Hawkins soon admits to Claudia that Harper is being "railroaded" and that Brisbane is bribing him to keep quiet. The next day, Hawkins is arrested and tells how the murder happened: Brisbane tried to make love to Myrtle in the back room but she resisted, hit her head after being pushed to the ground by him and was knocked unconscious. Believing that she had been badly hurt, Brisbane sent Hawkins to bring Myrtle to the front of the building, but she had died. Brisbane, who intended to frame Hawkins, instructed him to write incriminating notes, but decided to frame Harper instead when Hawkins bungled the story. Later, Claudia finds a witness, a young boy, who told his mother that George became angry after seeing Myrtle and Brisbane kissing in the back room and wanted to kill them both. When he found Myrtle unconscious, George killed her by strangling her with a rope and then fled. The case is solved, and after Henry discovers Claudia is not Catbird, he kisses her and promises to take her away from the "Catbird's nest."