Stuttering Bishop Mallory asks attorney Perry Mason for information about the crime of manslaughter. Twenty years earlier, he explains, a woman named Ida Gilbert killed a man in an auto accident. She was determined to be drunk at the time of the accident and her father-in-law, Ronald Brownley, an oil millionaire who had objected to her marriage to his son, had her charged with manslaughter. Ida fled to Australia, where because she could not afford to care for her daughter Janice, Ida allowed the bishop to find a home for Janice with a couple in Salt Lake City. Brownley, searching for his granddaughter, has discovered a woman named Janice Alma Brownley who claims to be his granddaughter. The bishop knows she is a fake, however, and wants Perry to help him find the real heiress. Although Perry is suspicious of the bishop because of his stutter, he takes the case. Then the bishop is attacked in his hotel room by Peter Sacks, who is involved with the false Janice, and decides to return to Australia. Ida and her friend, Stella Kenwood, come to town and are located, along with Janice Seaton, by Perry, his secretary, Della Street, and his detective, Paul Drake. Then Janice disappears and Perry learns that the bishop is not on the boat to Australia. Ida plans to show Brownley a watch that proves Janice Seaton is his real granddaughter, but then he is shot by a woman in a white raincoat before Ida can meet with him. His body and car then disappear, and later the car is found in the bay. Ida's gun is in the car, and she is arrested for his murder. Perry takes on her defense. Brownley's body is found and it is discovered that he actually died of drowning. Perry reveals that Stella, the mother of the imposter Janice, shot Brownley after stealing Ida's gun, hoping to implicate her. Brownley did not die from the gun shot. Later, Sacks and his crony Victor Stockton, who had planned to murder Brownley in order to cover up their deception, pushed his car into the bay where he drowned, making them the actual murderers. The bishop reappears and speaks without stammering, explaining that he only stutters when he is under emotional shock.