“I must ask you to say nothing about this matter,” the professor directed. “Under no circumstance could I permit a story to be written about my work.”
“But why?”
“Publicity at this time might rob me of an opportunity to sell the machine. A very prominent man, James Johnson, is now considering its purchase.”
“But I thought you were expecting to sell your invention to the government,” Penny said, puzzled.
Professor Bettenridge bit his lip. Obviously, he was beginning to share his wife’s annoyance at the girls.
“I regret I can’t tell you all the details of my negotiations,” he said. “My wife and I are very tired, so if you will excuse us—”
“Certainly,” said Penny, taking the hint. “Louise and I must be on our way to Riverview.”
They started to leave, but before they could reach the door, someone tapped lightly on it. Professor Bettenridge and his wife exchanged a quick glance which Penny could not fathom. For a fleeting instant, she thought they both looked frightened.
Then the professor went to the door and opened it. A little man in a derby hat and with an apologetic manner stood on the threshold.
“Mr. Johnson!” exclaimed the professor, extending his hand. “My wife and I did not expect you until tomorrow.”