Joe Powell, a publicity director for a film studio, visits his girlfriend Susan Cooper to spend a quiet evening together. The couple’s routine night takes a grim turn when a woman’s scream shatters the apartment building’s calm. They discover Ellen Smith, who lives across the hall, has been strangled in her own apartment, and the shock of the moment sets the pace for a string of troubling discoveries.
The case takes a sharper turn as Mona Harrison, an actress who had recently vanished, suddenly returns to headlines. At Mona’s home, police chief Williams conducts a thorough round of interviews with everyone who attended a dinner party the night before. The mood grows tense as Mona’s servants quit in a hurry, and the hostess herself had insisted on taking the group out to a restaurant—an invitation that never reaches the table. The mystery deepens with each question, each careless detail, and each whispered rumor.
Susan, drawn to the mystery, decides to search Mona’s bedroom and uncovers a hidden safe, a secret that signals there is more to Mona’s life than anyone realized. Her investigation takes a perilous turn when she hides in a closet as a man enters the room. The danger intensifies as the intruder closes in, and just as the threat seems to be closing in too tightly, Detective Hoffman arrives, jolting the moment and allowing the assailant to escape.
As the dust begins to settle, Joe and Susan learn a grim truth: Mona has been found dead, and the coroner’s verdict reveals a troubling contrast. Ellen was murdered by a man, while Mona’s death is attributed to a woman. This bizarre twist deepens the fear that someone close to Mona might be hiding a dangerous motive. Joe’s recent search through Mona’s files for mentions of her twin sister Marie nearly costs him his life, as he is almost ambushed while he studies the documents in his office.
With mounting alarm, Susan makes the difficult decision to leave for Reno, Nevada, seeking safety away from the escalating danger. Joe, along with Hamilton Hart and Carol Lynn, sets off to follow her to Reno, hoping to ensure her protection as the case grows more tangled. The journey is treacherous from the start, and Susan’s path is nearly cut off again when a near-miss on the road—driven by Arthur Evans, a figure connected to the surrounding web of blackmail and murder—threatens to derail her plans.
Arriving in Reno, Susan finally reunites with Joe, Carol, Hart, and Mona’s sister Marie at a hotel. In a tense confrontation, Susan reveals the shocking chain of manipulation: Arthur Evans had married Marie and, together, they used Mona as a pawn in a blackmail scheme. When Mona refused to pay further, Marie killed Mona, and Arthur killed Ellen as a witness to the crime. The web of deceit spirals into violence as Marie’s fury grows unchecked, and in a violent outburst, she unintentionally falls to her death from the hotel window, leaving the mystery unresolved in a way that hints at the consequences of the night’s dark secrets.
