"I mean the woman," replied Ling Chu quietly. "But who in God's name wanted to get into the house after murdering Mrs. Rider?" asked Whiteside irritably. "Your theory is against all reason, Ling Chu. When a person has committed a murder they want to put as much distance between themselves and the scene of the crime as they can in the shortest possible space of time." Ling Chu did not reply. "How many people are concerned in this murder?" said Tarling. "A bare-footed man or woman came in and killed Mrs. Rider; a second person made the round of the house, trying to get in through one of the windows----" "Whether it was one person or two I cannot tell," replied Ling Chu. Tarling made a further inspection of the little wing. It was, as Ling Chu had said and as he had explained to the Chinaman, cut off from the rest of the house, and had evidently been arranged to give Mr. Milburgh the necessary privacy upon his visits to Hertford. The wing consisted of three rooms; a bedroom, leading from the sitting-room, evidently used by Mrs. Rider, for her clothes were hanging in the wardrobe; the sitting-room in which the murder was committed, and the spare room through which he had passed with Odette to the gallery over the hall. It was through the door in this room that admission was secured to the house. "There's nothing to be done but to leave the local police in charge and get back to London," said Tarling when the inspection was concluded. "And arrest Milburgh," suggested Whiteside. "Do you accept Ling Chu's theory?" Tarling shook his head. "I am loath to reject it," he said, "because he is the most amazingly clever tracker. He can trace footmarks which are absolutely invisible to the eye, and he has a bushman's instinct which in the old days in China led to some extraordinary results." They returned to town by car, Ling Chu riding beside the chauffeur, smoking an interminable chain of cigarettes. Tarling spoke very little during the journey, his mind being fully occupied with the latest development of a mystery, the solution of which still evaded him. The route through London to Scotland Yard carried him through Cavendish Place, where the nursing home was situated in which Odette Rider lay. He stopped the car to make inquiries, and found that the girl had recovered from the frenzy of grief into which the terrible discovery of the morning had thrown her, and had fallen into a quiet sleep. "That's good news, anyway," he said, rejoining his companion. "I was half beside myself with anxiety." "You take a tremendous interest in Miss Rider, don't you?" asked Whiteside dryly. Tarling brindled, then laughed. "Oh, yes, I take an interest," he admitted, "but it is very natural." "Why natural?" asked Whiteside. "Because," replied Tarling deliberately, "Miss Rider is going to be my wife." "Oh!" said Whiteside in blank amazement, and had nothing more to say.