"That is one of the things I should like to know," he said, "and the very matter upon which Miss Rider refuses to enlighten me. I am taking her to an hotel," he went on. "To-morrow I will bring her down to the Yard. But I doubt if the Chief can say anything that will induce her to talk." "Was she surprised when you told her of the murder? Did she mention anybody's name?" asked Whiteside. Tarling hesitated, and then, for one of the few times in his life, he lied. "No," he said, "she was just upset ... she mentioned nobody." He took the girl by taxi to the quiet little hotel he had chosen--a journey not without its thrills, for the fog was now thick--and saw her comfortably fixed. "I can't be sufficiently grateful to you, Mr. Tarling, for your kindness," she said at parting "and if I could make your task any easier ... I would." He saw a spasm of pain pass across her face. "I don't understand it yet; it seems like a bad dream," she said half to herself. "I don't want to understand it somehow ... I want to forget, I want to forget!" "What do you want to forget?" asked Tarling. She shook her head. "Don't ask me," she said. "Please, please, don't ask me!" He walked down the big stairway, a greatly worried man. He had left the taxi at the door. To his surprise he found the cab had gone, and turned to the porter. "What happened to my taxi?" he said. "I didn't pay him off." "Your taxi, sir?" said the head porter. "I didn't see it go. I'll ask one of the boys." As assistant porter who had been in the street told a surprising tale. A gentleman had come up out of the murk, had paid off the taxi, which had disappeared. The witness to this proceeding had not seen the gentleman's face. All he knew was that this mysterious benefactor had walked away in an opposite direction to that in which the cab had gone, and had vanished into the night. Tarling frowned. "That's curious," he said. "Get me another taxi." "I'm afraid you'll find that difficult, sir." The hotel porter shook his head. "You see how the fog is--we always get them thick about here--it's rather late in the year for fogs..." Tarling cut short his lecture on meteorology, buttoned up his coat, and turned out of the hotel in the direction of the nearest underground station. The hotel to which he had taken the girl was situated in a quiet residential street, and at this hour of the night the street was deserted, and the fog added something to its normal loneliness. Tarling was not particularly well acquainted with London, but he had a rough idea of direction. The fog was thick, but he could see the blurred nimbus of a street lamp, and was midway between two of these when he heard a soft step behind him. It was the faintest shuffle of sound, and he turned quickly. Instinctively he threw up his hands and stepped aside. Something whizzed past his head and struck the pavement with a thud. "Sandbag," he noted mentally, and leapt at his assailant.