In San Francisco, Judge Wesley Armstrong is stabbed to death in his study by an intruder, and Victor Armstrong, the judge’s nephew, who has come to see him, is knocked unconscious by the same assailant as he answers the telephone in the study.
Police Lieutenant Mike Ruark is alerted by the judge’s secretary, Phyllis Powers, the person who had made the telephone call to the judge’s residence when Victor was attacked. As the police arrive at the Armstrong home, they discover Victor recovering consciousness and holding the murder knife in his hand.
Meanwhile, Tommy Chan, Charlie Chan’s second son, and Birmingham Brown, Chan’s chauffeur, are walking home from a movie when they witness an apparent burglary taking place as they see a man enter a house by climbing through a window. Unfortunately for the two amateur sleuths, it turns out that the “burglar” is the home’s owner, district attorney Frank Bronson, and they both end up spending the night in jail.
Later, Bates, Judge Armstrong’s butler, tells Bronson that the judge had denied Vic entrance to the house, and that Vic had sneaked in through a window. Phyllis then admits to Bronson that she had overheard Vic, her boyfriend, and the judge arguing about an unwise stock deal in which the former had invested $30,000 of his assets. The judge had called his lawyer, Ed Seward, arranging to meet him the next day to draw up a new will which would exclude his nephew who was his sole heir. Bronson assumes that if the judge had not been killed the night before, Victor would have been completely disinherited, thus making it appear that he had a clear motive for killing his uncle.
When Chan comes to see Bronson to apologize about the misadventure of Tommy and Birmingham, Bronson and Ruark receive word that two sets of fingerprints were found on the knife – Vic’s and Tony Pindello’s. Aware that Pindello had been executed at San Quentin Prison six months before, having been sentenced by judge Armstrong, Ruark asks for Chan’s help with the case.
Later, someone shoots and kills Bronson and removes papers that he was examining related to the Pindello case. Ruark tells Chan about Bronson’s murder and that Pindello’s fingerprints were found on Bronson’s desk.
At Judge Armstrong’s office, Chan and Ruark discover Walter Somervale, the judge’s clerk of court, going through papers in a filing cabinet. While Chan and Ruark examine the judge’s papers, Seward shows up and tells them that, before he became the judge’s personal attorney, he had defended Pindello in his murder trial. In the judge’s safe, are found papers regarding a commission investigating eacketeering in the insurance business, on which Seward is also serving. They also find a letter addressed to Vic, to be opened only in the event of the judge’s death. In the letter, Judge Armstrong states that he had uncovered evidence suggesting that Pindello may have been innocent and that he had intended to inform Bronson of this.
After Chan learns that Pindello was buried in a local cemetery, they go there and discover that the coffin has been removed. Chan then requests that all members of the Pindello jury be placed under police protection as he fears for their safety. However, Lt. Ruark fails to locate one juror, Thomas Cartwright.
Pat Finley, Ruark’s assistant, locates Cartwright’s new address but, before he can reach him, someone enters Cartwright’s room and slugs him with the butt of a pistol. When Finley arrives, he finds Cartwright dead by hanging. Once again, Pindello’s fingerprints are found at the crime scene. The third victim’s name, Chan notes, begins with the letter “C,” pointing to an alphabetical list of intended victims. Chan also tells Ruark that he thinks there could be a connection between the Pindello case and the insurance swindle.
After Chan discovers a method by which Pindello’s fingerprints might have been forged, he asks Ruark to arrange a meeting with Phyllis, Vic, and Seward at the judge’s home. While they are in the study, the lights go out, and a masked gunman locks them in a closet, then leaves. They manage to break out, and find that all of the papers relating to the Pindello case are missing.
Later, Chan discovers that a director of a funeral parlor has recently reburied a sealed coffin and obtains the address of the man who had arranged for the burial. Chan seeks out the address and breaks into the man’s room but is surprised by Joseph Pindello, Tony’s brother.
Later, Ruark assembles all of the principals in the case. Chan explains that Pindello had a brother, Joseph, who was in jail when Tony had written to him telling him that he was about to be executed for a crime that he had not committed. According to Chan, when Joseph was released from jail, he had dug up his brother’s body, and had intended to kill everyone who was associated with the execution.
As Chan explains this, Joseph enters, holds everyone at gunpoint, and says that he had simply intended to give his brother a proper burial. Before he can continue, he is tackled from behind by Tommy and is taken prisoner. However, Chan tells the group that Joseph is not the murderer of Armstrong, Bronson, or Cartwright, but that Seward is. Chan states that he was involved with Tony Pindello in an insurance swindle. Seward wanted all of the money, so he framed Tony for murder. Fearing that Armstrong and Bronson were about to discover this, Seward murdered them and also killed Cartwright to make it look like a series of murders. Seward grabs Joseph’s gun and explains how he had used Tony’s fingerprints to divert attention from himself. Chan then reveals that Joseph was part of the set-up that they have just gone through and that the gun in Seward’s hand is not loaded. Seward tries to flee, but runs into Birmingham and, in the confusion, is captured.