“There goes my Hippy’s roll!” cried Nora, and for the moment attention was centered on Lieutenant Wingate’s rolling boulder. It made a clean hit, knocking down a tree close to the water.
“The racket must be terrific down there,” said Grace. “Hippy, you surely raised a disturbance with that last shot.”
Tom tried once more and sent a boulder into the lake. The Overlanders plainly heard the impact, and could see a shower of broken rock being distributed over the surface of the lake.
Suddenly a new sound smote the ears of the Overland Riders, a familiar sound that they had heard many times in France and on their journeys in their own land.
“What’s that?” demanded Stacy.
“That?” answered Hippy. “Why, that is a butterfly lullaby. You surely ought to know that sound by this time.”
“Woo, woo, woo!” was the sound that smote their ears again.
“Down, all of you! We’re under fire!” shouted Tom Gray.
CHAPTER XX
LEAD AND MYSTERY IN THE AIR
“Are—are we attacked?” wailed Emma Dean.