Detective Mark McPherson interviews newspaper columnist Waldo Lydecker, a suspect in the homicide of Waldo's friend and protégé Laura Hunt, killed in her apartment by a disfiguring shotgun blast. Mark allows Waldo to accompany him as he interviews Laura's aunt, Ann Treadwell. Laura's fiance Shelby Carpenter is at Ann's place and it's clear Shelby and Ann are involved.
In flashback, Waldo tells how Laura impressed him with her integrity and how his high-society connections and her own hard work enabled her to rise to the top of her advertising company. When she dated an artist named Jacoby, jealous Waldo publicly attacked him in his column and Laura broke off the relationship. However, when Waldo revealed that fiance Shelby was dating a model, Diane Redfern, Laura refused to end the relationship. When Waldo and Laura discovered Shelby with Ann, Laura left to go to her country house to reconsider her engagement.
Mark finds a bottle of cheap Scotch in Laura's apartment, which her maid Bessie found the day after Laura's murder. Shelby and Ann show up at Laura's apartment but Shelby refuses to drink the Scotch.
Mark spends the night in Laura's apartment, gazing at her portrait, going through her things and becoming obsessed with her. Waldo visits and warns him his falling for a corpse will drive him insane. Mark falls asleep next to Laura's portrait. He awakes when Laura herself enters the apartment. She says she's been away alone at her country home and hadn't heard of her apparent murder because her radio was broken. Laura finds Diane Redfern's clothes in her closet. Mark and Laura speculate that in the dark apartment, the killer mistook Diane, who had dressed in Laura's negligee, for Laura. Mark asks Laura about Diane and Shelby, but Laura says that Diane meant nothing to Shelby. He also asks her about Shelby and she says she's decided to end the engagement.
Laura and Shelby meet, unaware they're being watched by the cops. Mark follows Shelby to Laura's country house and finds him with a shotgun that's been recently fired. Shelby says he'd hunted recently. Mark accuses Shelby of buying the cheap Scotch. Shelby confesses that he invited Diane over to Laura's apartment the night of the murder to end their affair. The doorbell rang and Shelby made Diane answer it. When she was killed, he panicked and fled. Mark asks Shelby if Laura killed Diane, but Shelby says he doesn't know. Mark accuses Laura of sending Shelby to get rid of the gun. He turns on the radio in her house and it works.
The next day, Mark finds that Laura's engagement to Shelby is on again. Waldo visits and faints when he sees Laura alive. Ann asks Shelby to marry her but he's more interested in Laura. Laura asks Shelby why he went to her country house and he says he wanted to get rid of the shotgun to protect her. She's horrified that he thinks she murdered Diane.
Mark takes Laura away to the police station. She denies killing Diane. He asks her about the working radio, which she says she asked a local handyman to fix as she left her country home. Mark is more interested in finding out why she didn't end the engagement with Shelby or if she told him she would end the engagement because that's why he wanted to hear. Laura tells Mark that ending the engagement would have signified that she thought Shelby the murderer. Once she tells him she's not in love with Shelby, he releases her.
Mark goes to Waldo's apartment and breaks the base of his antique clock, which is hollow but empty. At Laura's, Waldo attacks Mark's character, but Laura is attracted to Mark. Mark walks in and tells Laura her shotgun isn't the murder weapon. Tired of Waldo's jealousy, Laura ends their relationship and he leaves. Mark searches Waldo's second antique clock, which he gave to Laura, and finds the shotgun. He leaves the gun in the clock and kisses Laura goodnight.
Laura gets ready for bed. Waldo sneaks back into her apartment, retrieves the gun and tries to kill her in a jealous rage. Mark and another detective, not having seen Waldo leave her building, burst into Laura's apartment. The other detective shoots gun-wielding Waldo dead.