A khaki-clad figure appeared in the doorway, saluted smartly.
"Yes, Lieutenant?"
"Close that door, soldier, and see that it's kept—say! What is this, anyway? Why the gas-mask?"
The guard's voice was weirdly muffled by his rubbery face covering.
"Orders, sir. Trial blackout and mock gas attack in fifteen minutes, sir. All men on duty have been ordered into masks, sir."
"So?" Steve Duane stared at the guard thoughtfully. "Well, in that case, you may resume your post. But this time close the door carefully. Oh, and by the way, soldier—"
He spoke with studied casualness as the guard turned away. The other man glanced back.
"Yes, Lieutenant?"
"You might be kind enough to—Achtung!"