Ruth Robin is the daughter of a millionaire, and is attending a seminary for girls at the time the story opens. Her father, Daniel Robin, is a recluse and lives in perpetual fear of death at the hands of a criminal band known as the "Terrible Thirteen." He has been forced Into membership of this band against his will. Daniel Robin is shot from behind by LaFarge, the leader of the "Terrible Thirteen," who is known as the Hound. While on his death bed Mr. Robin has his daughter summoned. He tells her in the presence of his trusted butler, Wayman, that she must recover a Peacock Fan stolen by the band, as it contains a secret affecting her. She must also accept thirteen separate keys as they are handed to her by an unknown hand, and follow the Instructions in each instance. Ruth agrees to these terms, and after her father's death starts out on the first mission. It takes her to the home of the Countess Zitka, where she finds the Peacock Fan. Later, she is forced to invade the headquarters of the "Terrible Thirteen," and still later another key takes her into the heart of Chinatown.