and in your case I'm convinced they'll all be...." 

"Don't say it," he said hastily. "I don't need to read your brain waves to know what you're thinking." 

"Nor do I need this machine to know what you are usually thinking of," she finished. "Now lie down and relax. I'm going to give you the lowest voltage first. I still don't think you are right in saying there's no real danger." 

He lay back and closed his eyes. 

Swiftly she went about, making adjustments, turning rheostats, watching indications on meters with narrowed eyes. Then, with a final check over the entire apparatus, she switched on the machine to lowest voltage. 

Slowly the tubes warmed up, then there came a slight crackling from the loudspeaker, developing swiftly into a hum that rose and fell in a musical pattern. The green bands on the oscilloscope danced in time to the hum from the loudspeaker, and on the television screen an image began to form. By stages it grew, at first seeming to be a wavering white pillar, then a ghostly form, like a sheeted figure in a graveyard, then suddenly it began to clarify. A face emerged into view, and Mary almost gasped as she recognized it as her own. But the rest of the picture remained shadowy and indistinct. 

"More power," murmured Mary. She turned the rheostat up a trifle further, and the hum from the loudspeaker became even louder, more vibrant. On the screen the rest of the dancing figure coalesced and suddenly Mary jumped back from the screen. She turned toward Jensen where he lay, relaxing with a slight smile on his face, and uttered an exclamation. 

"Don, you stop that!" She reached for the electrode to snatch it indignantly from his head. As she did so her fingers touched the metal. A bright flash came from the silver disk, raced up her arm, and her muscles tightened in shock. Her voice rose suddenly in a scream, and then, as Jensen jerked violently under her hands, everything went black. She slumped beside him, unconscious, and the hum from the loudspeaker took on a higher, treble note that filled the whole laboratory with its vibrant pulsations.High over the valley came a keening note, drifting down the wind with a strange, heterodyning effect. It rose and fell with a definite cadence, as though it were a message.

Out of the murky darkness at the far end came a stirring; a gigantic groping, as of a monstrous something responding sluggishly to the call. Then, more 

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