"Come in, Andy."
But the voice that answered as the door was flung open was not Andy's. Instead, it was a deep, resounding bass one.
"I'm not Andy; but I'll accept the invitation."
As the owner of the voice, a tall, well-set-up man with a military bearing, stepped into the room all the Scouts sprang erect at attention, and gave the Scout salute. Then they broke into three cheers.
"Why, Lieutenant Duvall, what are you doing here?" exclaimed Rob, coming forward.
The young officer shook hands warmly with the leader of the Boy Scouts. Then, while the others pressed closer to the lieutenant—the same officer who had conducted the aviation tests at the "tunnelled house"—he addressed Rob.
"The fact is, I came down here to see if you are willing to tackle some more adventures," he said.
"Are we—" began Rob; but a roar from the Scouts interrupted him.
"Just you try us, Lieutenant."
"More adventures? Great stuff!"