“_All Frogs listen. Mills is dead. Number Seven finished him this morning. Number Seven receives a bonus of a hundred pounds._” The voice was clear and singularly sweet. It was a woman’s. “_Twenty-third district will arrange to receive Number Seven’s instructions at the usual place._” Dick’s heart was beating thunderously. He recognized the speaker, knew the soft cadences, the gentle intonations. There could be no doubt at all: it was Ella Bennett’s voice! Dick felt a sudden sensation of sickness, but, looking across the table and seeing Elk’s eyes fixed upon him, he made an effort to control his emotions. “There doesn’t seem to be any more coming through,” said the operator after a few minutes’ wait. Dick took off the headpiece and rose. “We must wait for the direction signals to come through,” he said as steadily as he could. Presently they began to arrive, and were worked out by a naval officer on a large scale map. “The broadcasting station is in London,” he said. “All the lines meet somewhere in the West End, I should imagine; possibly in the very heart of town. Did you find any difficulty in picking up the Frog call?” he asked the operator. “Yes, sir,” said the man. “I think they were sending from very close at hand.” “In what part of town would you say it would be?” asked Elk. The officer indicated a pencil mark that he had ruled across the page. “It is somewhere on this mark,” he said, and Elk, peering over, saw that the line passed through Cavendish Square and Cavendish Place and that, whilst the Portsmouth line missed Cavendish Place only by a block, the Harwich line crossed the Plymouth line a little to the south of the square. “Caverley House, obviously,” said Dick. He wanted to get out in the open, he wanted to talk, to discuss this monstrous thing with Elk. Had the detective also recognized the voice, he wondered? Any doubt he had on that point was set at rest. He had hardly reached Whitehall before Elk said: “Sounded very like a friend of ours, Captain Gordon?” Dick made no reply. “Very like,” said Elk as if he were speaking half to himself. “In fact, I’ll take any number of oaths that I know the young lady who was talking for old man Frog.” “Why should she do it?” groaned Dick. “Why, for the love of heaven, should she do it?” “I remember years ago hearing her,” said Elk reminiscently. Dick Gordon stopped, and, turning, glared at the other. “You remember . . . what do you mean?” he demanded.