r. Bird shook his head.
"Too thin, Carney, old dear," he said. "Breslau is a very intelligent young man. He was perfectly normal when I left him shortly after midnight last night. He was working alone in here on a device of the utmost military importance. On the desk is a push button which sets ringing a dozen gongs in the building. Surely a man of that type would have had sense enough when he heard and saw intruders cutting a hole through the roof to sound an alarm which would have brought every watchman on the grounds to his assistance. He must have been knocked out before the hole was started, probably before the helicopter's landing."
"How? Gas of some sort?"
"The windows were all closed and locked and I have already ascertained that the gas and water lines have not been tampered with. Gas won't penetrate through a solid roof in sufficient concentration to knock out a man like that. It was something more subtle than gas."
"What was it?"
"I don't know yet. The clue to what it was lies, as I told you, in those windows."
Carnes moved over and surveyed the windows closely.
"I see nothing unusual about them except that they need washing rather badly."