During a broadcast of radio personality Victor Grandison's show, Roslyn White, his secretary, is found hanged in his office. At the same time, his niece, Althea Keane, holds a party in honor of his birthday. The unexpected arrival of Steven Francis Howard, who claims to have been married to Matilda Frazier, Victor's other niece, interrupts the party. Matilda, who was engaged to marry Althea's husband Oliver, went abroad to get over his loss, and is thought to have drowned after a shipwreck. When Victor arrives with Jane Moynihan, his director, he is stunned to learn about Matilda's marriage, especially because her estate is about to be settled. Steven informs Victor that he knew nothing about Matilda's money, but in any case, is a wealthy man in his own right. Victor then invites Steven to stay in his home while policeman Richard Donovan secretly investigates his story. Meanwhile, Victor receives a telegram from Matilda, who was rescued and hospitalized in Brazil. Steven meets Matilda's plane, but she does not remember him or the marriage. To her surprise, however, he knows all about her and the others in the family. To corroborate his claims, he takes her to the justice of the peace who married them. Although the man recognizes Matilda, nothing seems familiar to her. Later, Matilda and Althea quarrel over Oliver, who is now drinking heavily. Still suspicious of Steven, Victor goes through his clothes and finds a snapshot of Roslyn. Elsewhere, Steven meets secretly with Jane, who is convinced that Roslyn did not commit suicide and shows him a letter that implicates Victor in her death. Steven then shows the letter to a skeptical Donovan, who explains that Victor was broadcasting at the time of Roslyn's death. Later, Victor overhears Althea tell Steven that she telephoned Roslyn the night of her death and heard her scream. Victor then records a quarrel between Oliver and Althea during which Oliver threatens to kill her, and afterward orders Oliver to leave the house. Under questioning, Althea tells Victor that she believes he killed Roslyn. Victor admits that he killed Roslyn when she discovered that he had misused Matilda's estate and then kills Althea, making it appear as if the killer was Oliver. Later, Victor cuts the brakeline on Oliver's car, and he dies in the ensuing accident. Steven tells Matilda that he has deceived her about their marriage. Explaining that he had been engaged to marry Roslyn, who he believes did not commit suicide, Steven warns Matilda that she is also in danger. Matilda, however, refuses to believe that Victor is behind the deaths. After he learns that Matilda is in love with Steven, Victor tricks her into writing a suicide note, which he intends to use to cover up her murder. When Victor discovers Steven with the recording he made of Oliver and Althea, he blackmails Press, a murderer, into kidnapping Steve and then gives Matilda a poisoned drink. The drink does not kill her, however, and when she regains consciousness, she realizes that Steven was telling the truth and calls the police. With her help, they find an unconscious Steven in a garbage dump, where Press has left him to be crushed to death. Realizing that he can no longer escape, Victor then confesses to his crimes during his final broadcast.