In The Case of Murder and the Bloodstained Necklace, Mr. Keen, the renowned tracer of lost persons, is drawn into a chilling murder investigation when Grace Bradley is found dead in her hotel room. The scene is grim; she lies lifeless with a bullet wound to her throat and a string of pearls clutched tightly in her hand. Her friend, Mrs. Thornton, seeks Keen's help, revealing that Grace had recently lost her wealthy husband and had come to New York to start anew. The police are baffled by the pearls, which seem to contradict Grace's modest lifestyle.