A blackmailer's murder tears apart a well-off family.
Hated by everyone in his family, Bayard Thatcher offers to leave if the family will pay him to do so. When they hesitate, he reminds them that he knows something about every one of them which he will reveal if the money isn't paid. That evening Bayard is shot. Pretending that he was wounded while cleaning his gun, the family sends for Dr. Allen Carick, who dresses the wound and leaves nurse Sally Keating to care for Bayard. Bayard tells Sally that his injury was not an accident. She also learns that Janice Thatcher, the wife of Dave Thatcher, is in love with the district attorney, John Tweed. When Sally tells Carick what she has learned, he asks her to leave the Thatcher home, but she is determined to get to the bottom of the mystery. Bayard announces his departure that evening even though Carick advises against it, and sends Sally away for the afternoon. She spends the time in the garden reading. While she is there she sees a frightened dog run from the house. Adela Thatcher follows the dog and explains she punished him when he broke a vase. Sally also sees Dave, who was supposed to be fishing with John Tweed. When everyone returns home, they find that Bayard has been murdered. After confusion and denials from everyone, during which Dave dies from an overdose of drugs, Sally realizes that Bayard was shot when the mail plane flew overhead at 3:20 p.m., even though Adela claimed to have spoken with him from the drugstore at 4:00. It is revealed that Adela made the murder scene look as if there had been a robbery to cover the crime and broke a vase to explain the dog's fear after hearing the shot. She then faked a phone call to give herself an alibi. She committed the murder to save Dave, a drug addict who was getting his drugs from Bayard. Tweed then arrests Adela, who dies from a heart attack before she can be taken away. The mystery is solved and now Tweed and Janice and Carick and Sally can be married.
