"Thanks, Doctor."
The detective returned in ten minutes with a worried expression.
"She wasn't in your office, Doctor," he reported.
"Who? Oh, Thelma. Where was she?"
"No one seems to know. She left yesterday afternoon and hasn't returned."
"Oh, well, since I am out of the city, I expect she decided to take a vacation. Women are always undependable. Did you get hold of the rest?"
"They'll be down at midnight, all but Davis. He'll come down in the morning."
"Good enough! Now, Colonel, if you'll have the officers who are going out to-morrow assembled, we'll divide the territory and make our plans for the search."
A week later, the situation was unchanged. Secret service operatives and soldiers from the Proving Ground had covered, foot by foot, square miles of territory south of the Proving Ground, but without result. Not a single unexplainable thing had been found. Sensitive instruments sent down from the Bureau of Standards, instruments so sensitive that they would detect an electric light burning a mile away, had yielded no results. As a final measure, General Merton had ordered a dozen planes with steel-cylindered motors to the Proving Ground and they had repeatedly crisscrossed the suspected territory, but had acquired no static charge large enough to affect them. It was evident that Saranoff's device, if it existed, had been moved, or else was not in operation.