While investigating the brutal murder of Laura Hunt, New York police lieutenant Mark McPherson calls on erudite columnist Waldo Lydecker, a close friend of the dead woman. Waldo knows of Mark from his heroic battles with gangsters, and Mark points out that Waldo once wrote a story about a murder committed with a shotgun loaded with buckshot--the very way that Laura was killed. Claiming to be intrigued by crime, Waldo asks to accompany Mark on his investigation, and the two men call on Laura's aunt, the wealthy Ann Treadwell. Mark inquires about Ann's relationship with Laura's fiancé, Shelby Carpenter, citing evidence that she has been giving him money. Just then, Shelby, a charming Southerner, arrives and says that he and Laura were to have been married that week, but Waldo insists that when Laura canceled their dinner date on the night of the murder, she had not yet decided whether to go through with the wedding. Shelby accompanies Mark and Waldo to Laura's apartment, where the murder occurred, and after Shelby reluctantly hands over the key to Laura's country home, Waldo accuses him of the murder. Later, Waldo takes Mark to a restaurant and recalls how he met Laura five years earlier: Waldo is dining alone at the Algonquin when he is approached by Laura, an eager young employee of an advertising agency. Laura asks Waldo to endorse a pen for her company, and is hurt and disillusioned when he rudely dismisses her. Unable to get her out of his mind, Waldo later goes to see Laura at the agency, where he apologizes and agrees to the endorsement. They become friends, and under Waldo's tutelage, Laura rises in her profession and society. Although their relationship is platonic, Waldo is jealous of her suitors, and uses both his column and his influence over her to keep any rivals for her affections at bay. One night, at one of Ann's parties, Laura meets Shelby, who confesses that his family has been bankrupt for years. Laura gives him a job at the advertising agency, and they soon become romantically involved. Waldo has Shelby investigated and informs Laura that her fiancé is seeing a model, Diane Redfern. Laura is furious at Waldo's interference and dismisses the accusations until he produces a gold cigarette case that she gave Shelby, saying he retrieved it after Diane pawned it. Back in the restaurant, Waldo tells Mark that Laura had lunch with Diane the day of her death, and had planned to go to her country home for a few days. The following night, Mark, who is growing obsessed with Laura, returns to the apartment and continues searching through her personal effects. Waldo stops in and says he knows Mark has secretly put in a bid for Laura's portrait, and chides him for falling in love with a corpse. After Waldo leaves, Mark falls asleep under the portrait. He awakens to the sound of someone entering the room, and looks up to see Laura standing before him. Laura, who has been isolated in the country, is stunned when Mark shows her a newspaper story about her "murder." Laura then discovers one of Diane's dresses in her closet, and Mark concludes that the murder victim, whose face was damaged beyond recognition, was actually Diane. Mark questions Laura, brightening when she says she had decided not to marry Shelby, and instructs her not to leave the apartment or use the phone. As soon as Mark leaves, however, Laura calls Shelby, unaware that the police have tapped her phone. Shelby and Laura meet briefly, and Mark follows Shelby to Laura's country home, where he finds him removing a shotgun from a rack. Shelby claims that he had brought Diane to Laura's apartment to talk, but when Diane answered the door and was shot to death, he panicked and fled. Later, at a party to celebrate her return, Laura asks Shelby why he went to the cottage, and when he replies that he went to hide the shotgun, she realizes with horror that Shelby believes she is the murderer. Mark takes Laura into custody in front of her guests, but after questioning her at the police station, is convinced of her innocence. After taking Laura home, Mark searches Waldo's house and discovers a hollow compartment in his grandfather clock. He then goes to Laura's apartment and announces that her gun was not the one used in the murder. Resentful of the growing bond between Laura and the handsome detective, Waldo insults Mark, and Laura coolly sends her old friend away. Mark examines Laura's clock, which is a duplicate of the one in Waldo's home, and finds a shotgun hidden inside. He tells Laura that Waldo killed Diane, thinking it was Laura, and hid the gun in the clock after Shelby ran out. After kissing Laura goodnight, Mark locks her in and leaves, and Laura prepares for bed, unaware that Waldo has come back into the apartment through the service entrance. Waldo enters Laura's room and is about to shoot her when Mark and his men break in. Waldo is shot by the police and dies with Laura's name on his lips.