One of the volumes was locked. It was the newest of the books, and evidently an attempt had been made to force the lock, for the hasp was badly wrenched. Mr. Milburgh had, in fact, made such an attempt, but as he was engaged in a systematic study of the diaries from the beginning he had eventually put aside the last volume after an unsuccessful effort to break the fastening. "Is there nothing else?" asked Tarling. "Nothing," said the disappointed inspector, looking into the interior. "There may be other little cupboards of this kind," he added. But a long search revealed no further hiding-place. "Nothing more is to be done here," said Tarling. "Keep one of your men in the house in case Milburgh turns up. Personally I doubt very much whether he will put in an appearance." "Do you think the girl has frightened him?" "I think it is extremely likely," said Tarling. "I will make an inquiry at the Stores, but I don't suppose he will be there either." This surmise proved to be correct. Nobody at Lyne's Store had seen the manager or received word as to his whereabouts. Milburgh had disappeared as though the ground had opened and swallowed him. No time was lost by Scotland Yard in communicating particulars of the wanted man to every police station in England. Within twenty-four hours his description and photograph were in the hands of every chief constable; and if he had not succeeded in leaving the country--which was unlikely--during the time between the issue of the warrant and his leaving Tarling's room in Hertford, his arrest was inevitable. At five o'clock that afternoon came a new clue. A pair of ladies' shoes, mud-stained and worn, had been discovered in a ditch on the Hertford road, four miles from the house where the latest murder had been committed. This news came by telephone from the Chief of the Hertford Constabulary, with the further information that the shoes had been despatched to Scotland Yard by special messenger. It was half-past seven when the little parcel was deposited on Tarling's table. He stripped the package of its paper, opened the lid of the cardboard box, and took out a distorted-looking slipper which had seen better days. "A woman's, undoubtedly," he said. "Do you note the crescent-shaped heel." "Look!" said Whiteside, pointing to some stains on the whitey-brown inner sock. "That supports Ling Chu's theory. The feet of the person who wore these were bleeding." Tailing examined the slippers and nodded. He turned up the tongue in search of the maker's name, and the shoe dropped from his hand. "What's on earth the matter?" asked Whiteside, and picked it up. He looked and laughed helplessly; for on the inside of the tongue was a tiny label bearing the name of a London shoemaker, and beneath, written in ink, "Miss O. Rider." CHAPTER XXX WHO KILLED MRS. RIDER?