In the upstairs theatre office, Valerie Stanton, Rosalind Russell, a Broadway actress, tells Gordon Dunning, Leon Ames, her producer and former lover, about her intention to marry architect Michael Morrell, Leo Genn. Gordon threatens to tell Michael about her sordid past and grabs Valerie, wanting their relationship to continue. Valerie refuses and strikes Gordon with his statuette. Realizing that Gordon is dead, Valerie leaves the office without being seen and says goodbye to the cast on the closing night of their latest play. Meanwhile, Valerie's rival Marian Webster, Claire Trevor, finds Gordon's lifeless body.
Valerie returns to her apartment, where Michael Morrell, Leo Genn, calls about Gordon's absence. In distress, Valerie falls asleep as she memory-palaces the events leading up to his death.
One night, after finishing a play, Valerie tells Gordon about her interest in appearing in rival producer Peter Gunther, Walter Kingsford,'s upcoming revival of Hedda Gabler to prove her versatility as an actress. Gordon wants Valerie to continue appearing in his comedies. They attend Gordon's party, where Valerie meets Michael Morrell, and the spark between them rekindles.
The next day, Valerie dines with Michael and develops a romantic attraction. Later that night, Valerie calls Marian into her dressing room and allows Marian to pursue Gordon as she pleases. However, Gordon's feelings toward Valerie rekindle when she and Michael also arrive at the Sardi's restaurant. On the closing night of the play, Valerie reads columnist Jeff Trent's Dan Tobin article, reporting that she will appear in Dunning's new comedic play Madly in Love in tomorrow's newspaper. Valerie confronts Gordon in his office as he did not consult her beforehand. She demands that Gordon issue a retraction, but he refuses. The argument evidently leads to Gordon's death. Valerie suddenly wakes up as her housemaid Nancy, Theresa Harris, notifies her about Gordon's death.
A police sergeant arrives at Valerie's apartment and notifies her that Captain Danbury, Sydney Greenstreet, has called the theater personnel to report their whereabouts during Gordon's murder. At the theater, Marian, who has been hospitalized, is implicated as the prime suspect. When the interrogation concludes, Danbury brings Valerie to Gordon's office and shows her a letter Gordon had written rejecting Marian's love. Danbury also states Marian's fingers were on the statuette. Valerie returns to her apartment and tells Michael she believes in Marian's innocence. However, Michael believes Marian can defend her own innocence and proposes to marry Valerie.
Michael invites Danbury to Valerie's interview with Jeff. As Michael converses with Danbury outside, Valerie postpones the interview. She then tells a hypothetical theory in which she could have killed Gordon. However, Danbury dismisses the theory as she lacks a motivation. Sometime later, Valerie visits Marian in her hospital room. Marian has guessed Valerie had killed Gordon and denounces her as a remorseless killer. Valerie goes to Danbury's office to confess until she learns that Marian has killed herself.
Under heavy distress, Valerie is unable to concentrate during rehearsals and runs back home. On the opening night of Valerie's new play, Danbury arrives at Valerie stating that the investigation is closed, with Marian having killed Gordon. Trapped in her own guilt, Valerie walks about the theater until Michael confesses he already knew the truth. As the play progresses to the final act, Valerie writes a letter of confession, which Danbury finds in her velvet gloves. When the play finishes, Valerie turns herself in but receives her final standing ovation.
