"Why, these 'magic-eyes' are almost human," she commented in an undertone to Susan. "They turn lights on and off, cook meals, and open doors, when a beam of light strikes the cell——"
"I've heard of them before," Susan interrupted in a tone which clearly implied that she was not in the least interested.
Penny took the hint and dropped the subject. But she became absorbed in the article. When she closed the magazine a half hour later, her face was flushed with excitement.
"Susan, let's get away from here," she proposed in a whisper. "I've just had an inspiration!"
Grumbling a little at being forced to leave a fascinating story before she had finished it, Susan followed her friend from the building.
"What about this inspiration of yours?" she demanded as they walked to Penny's parked roadster.
"It's this way, Susan. I knew there was a logical explanation for the mysterious disappearance of that car Rap Molberg was driving. Let's go over to the Hamilton Factory this minute and test out my new theory."
"You may know what you're talking about, but I'm sure I don't, Penny Nichols."
"That's because you wouldn't let me tell you about that article I was reading," Penny laughed. "But I'll explain everything as we go along."
Without pausing to consider that it might not be safe to investigate the abandoned manufacturing plant at such a late hour, the girls drove directly into the hilly section of Belton City. Penny turned into the familiar dead-end street and was relieved to find no sign of other vehicles.