But Bentley's heart was filled to overflowing with gratitude that he had been able to safeguard Ellen against Barter. He never doubted it had been Barter who had telephoned her. And even now he fancied he could hear Barter's chuckle of amusement. Barter was watching, perhaps even listening. Bentley felt that the madman was just biding his time. Barter could have taken Ellen in this attempt, but hadn't tried greatly, knowing himself invincible, knowing that he could take her at any moment if it was necessary. And he might take her even if it were not necessary, since he had warned Bentley she must be removed. The police car raced back uptown so that Bentley could inform himself of any new developments in the Hervey case. Ellen snuggled against him gratefully. "You'll have to stick close to me," said Bentley, "until something happens, or until the exigencies of service draw me away from you. Then it will be up to Tom Tyler to look after you." "I can look after myself," she retorted spiritedly. "I'm over age and not without brains...." "Yet you went to Washington Square," said Bentley gently. "Didn't it even seem strange to you that I would have selected such a place as a rendezvous?" - - - Ellen turned away from him and her lips trembled. His gentle thrust had hurt her. "But I would have sworn it was your voice, Lee," she said. "And--I still think it was!" "I tell you I didn't phone you to meet me in Washington Square!" "But you told me you had talked with Barter for a long time on the headquarters phone, didn't you? Remember that you are dealing with the cleverest and maddest brain we know of to-day. What if he had merely talked with you to get a record of your voice? Suppose a voice were composed of certain ingredients, certain sounds. Suppose those ingredients could somehow be captured on a sensitized plate of some kind! Edison would have been burned as a sorcerer a few centuries before he invented the wax record. Twenty years ago who would have thought of talking pictures ... voices permanently recorded on celluloid?" "But the talkie films merely parrot, over and over again, the words of actual people. When I talked with Barter this morning I certainly said nothing about meeting you at Washington Square." "But the tone, the timber, the frequency of your voice! Lee, suppose he had gone a step further than the talkies and had found a way to break the voice apart and put it back together to suit himself...?" "Good Lord, Ellen! It sounds crazy ... but if you would have sworn that voice was mine, then mine it may have been, speaking words with my voice that I never spoke personally. But wait until we find out for sure. We're just guessing." But the idea stuck in his mind and he believed in it enough to tell Tyler, upon arriving at the Hervey residence, to warn every man named on the list of the Mind Master to make no appointments over the telephone, no matter how sure they were of the voices at the other end of the wire.