NYPD Det. Mark McPherson pays a visit to renowned newspaper columnist Waldo Lydecker as part of his investigation into the rather nasty unsolved murder of Laura Hunt, a young woman whom Lydecker took on as his protégé. Lydecker recognizes the detective from his former glory days as a gangbuster to which the detective responds by pointing out that Waldo wrote a column once about a murderer whose choice of weapon was shotgun loaded with buckshot which just so happens to replicate the means by which Laura Hunt was dispatched from the realm of the living.
Waldo counters by admitting his fascination with murder which leads to querying whether Mark would allow him to accompany the detective on his investigative route. That route leads next to Ann Treadwell, a Big Apple socialite who is not only Laura’s aunt, but the woman who introduced her niece to the man who became her fiancé, Shelby Carpenter. Mark brings up that relationship by revealing his knowledge that she has been supplying him with money. At that point, who should show up but Shelby himself, who insists that he and Laura were to have been wed that very week. Waldo, however, tells a different story: the very night that Laura was murdered she told Waldo that she wasn’t yet decided on whether she wanted to go through with the wedding.
When the detective heads off to investigate the scene of the murder at Laura’s apartment, he is accompanied by Shelby as well as Lydecker. Shelby hesitantly turns over the keys to Laura’s country home to Mark and Waldo accuses Shelby of murdering Laura. This sets the stage for Waldo to relate to Mark how he met Laura which is told in an extended flashback.
Waldo was dining conspicuously in his regular spot at the famous Algonquin when approached by a strikingly attractive young brunette woman with an overbite so slight as to be sexy. She wants Waldo to endorse a pen made her employer, but Waldo treats her as scornfully as he treats anyone else, seeming not to recognize her attractive qualities as any particularly standout. Only after a curt and imperious dismissal does he ruminate over the appearance of the girl and realize she will not leave his mind. Later he actively seeks her out at her job and graciously—if rather melodramatically—apologizes for his rudeness.
The flashback continues through a series of events that reveal the girl—who is Laura Hunt, of course—rising from her lowly place in the hierarchy of society to a position far more elevated as a result of her famous and influential mentor. Laura attends a party at her aunt’s and begins her relationship with Shelby. As he has done with every other man she has gotten romantically attached to, Waldo furtively investigates Shelby’s background and informs Laura that he is also currently involved with a model named Diane Redfern. Laura does not react as expected, expressing anger at Waldo’s interference rather than Shelby’s infidelity. Only after Waldo shows her a gold cigarette case that Laura has presented as a gift to Shelby which was in turn given to Diane who in turn pawned it for quick cash does she even seem to believe the accusations are true. Waldo then admits Laura lunched with Diane and was then to head to her country home for a few days. That plan was interrupted by her murder, of course.
Mark, in the meantime, has joined Waldo in his latest obsession with the young woman. The next night finds him returning to Laura’s apartment to search through her belongings just as much as to gaze at the large portrait of the dead woman hanging on the wall. Waldo shows up and lets know Mark know that he knows that Mark has secretly made a bid to purchase that very portrait. He then kids Mark for falling for a dead girl. Waldo leaves and Mark falls asleep still inside Laura’s apartment.
He is awakened by the sound of someone entering the apartment and when he looks up to see who else seems to have a key to Laura’s home he is stunned into silence by the sight of the girl whose portrait hangs nearby. A girl who is supposed to be very much dead.
In fact, Laura did make it to her country home where she has enjoyed utter isolation from friends and news reports. Only when Mark shows her a newspaper account of her own murder does she realize what has happened and why a strange police officer is sleeping in her apartment. Upon discovering a dress that belonged to Diane Redfern hanging in her closet, Mark realizes that the woman whose face was obliterated by the shotgun blast must have been Shelby’s little fling. Mark now realizes he must consider Laura Hunt a suspect in what has up to know been the murder of Laura Hunt. What he seems to take away from his questioning, however, is that Laura has finally made a decision on the subject of marrying Shelby: the wedding is off permanently.
No sooner has the detective left, however, than Laura is on the horn to Shelby, both unaware that the line is being tapped by police. Later she and Shelby reunite briefly and then Mark trails Shelby up to Laura’s country home where he catches him taking a shotgun from a rack. Shelby’s explanation is that he had taken Diane to Laura’s apartment for a talk when someone came to door. When Diane opened the door, a shotgun went off which caused him to panic and flee.
A party is held to celebrate the return of a living Laura and she takes this opportunity to ask Shelby why he went up to the country house. His answer about hiding the shotgun makes it clear to Laura that he thinks she killed Diane. Mark shows up and arrests her, removing her from the party in his custody for questioning which, it turns out, utterly convinces him that she did not kill Diane. He then takes her back to her apartment before conducting a search of Waldo’s home in which he discovers a hidden compartment inside a grandfather clock. Mark makes a beeline back to Laura’s where he spotted an identical grandfather clock.
Waldo has become every bit as unhappy with Laura’s growing closeness to Mark as he was with Shelby’s despite exhibiting signs that he is probably homosexual and so neither man poses a sexual threat to his relationship with her. This sullen attitude erupts in a display of scornful superiority toward Mark which in turn results in Laura coldly informing Waldo he should leave. With Waldo gone, Mark investigates the clock and discovers that a shotgun inside the secret compartment. He informs Laura that Waldo intended to shoot Laura, but killed Diane by mistake and then hid the gun in her clock after Shelby fled. Laura kisses Mark who locks her safely inside. As Laura begins dressing for bed, Waldo sneaks back into her apartment through the service entrance with shotgun in hand. He is just about to complete the job he botched the first time around when Mark and the guard outside who has informed him Waldo Lydecker never left break in. The guard takes him and fire and Waldo subsequently dies with his last words being Laura’s name.